AU592671B2 - Phosphate coating composition and method of applying a zinc-nickel phosphate coating - Google Patents

Description

I iu Michigan, Michigan, uis U. S, day of Octobrci 1987 of INOIIC -,%41lliailon of vtfcrurim ure is requiiinai, Donald Lee Miles, COMMONWEALTH OF AUSTRALIA 9 A t- A fl f d<r f lflf d4r/*t^^r w r C-414i74 2 6 71 tess^wmsESxf^w.'.f r-aieins MCI, I D IiO q COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Class Int, Class Application Number Lodged Complete Application No.

Specification Lodged Published Priority: It.1 ;f S .T ll, P, %i r i Related art: 4 Name of Applicant: Address of Applicant: Olt Actual Inventor: Addre* for Service: Adde~s for Service: TO BE COMPLETED BY APPLICANT CHEMFIL CORPORATION 1300 Piedmont Troy, Michigan 48084, United States of America Harry Randolph Charles and Thomas Wilson Cape Care of COLLISON 117 King William ADELAIDE, S.A.

CO.,

Street, 5000 Complete Specification for the invention entitled: PHOSPHATE COATING COMPOSITION AND METHOD OF APPLYING A ZINC-NICKEL PHOSPHATE COATING The following statement is a full description of this invention, including the best method of performing it known to US t tr PHOSPHATE COATING COMPOSITION AND METHOD OF APPLYING A ZINC-NICKEL PHOSPHATE COATING I. Field of the Invention The present invention relates to a composition and method of applying an alkali-resistant phosphate coating on metal substrates which include zinciferrous coatings. More particularly, the present invention relates to nickel-zinc phosphate conversion coating compositions prepared from concentrates wherein a substantially saturated solution, having a balance of monovalent non-coating metal ions and divalent coating metal ions, such as zinc, nickel or manganese form a coating upon the metal substrates.

:0 II. Background of the Invention 0 O 0 Conversion coatings are used to promote paint adhesion and .IG: improve the resistance of painted substrates to corrosion. One type of conversion coating is a zinc phosphate conversion coating oo 0 *0 which is composed primarily of hopeite [Zn 3 (PO4)2]. Zinc phosphate coatings formed primarily of hopeite are soluble in alkali solutions. Such conversion coatings are generally painted which prevents the conversion coating from dissolving. However, if the S paint coating is chipped or scratched, the zinc phosphate coating is then exposed and subject to attack by alkaline solutions such as salt water. When the conversion coating is dissolved, the o underlying substrate is subject to corrosion.

la" 0 4 It*< r i cr--I In the design and manufacture of automobiles, a primary objective is to produce vehicles which have more than five-year cosmetic corrosion resistance. To achieve this objective, the percentage of zinc-coated steels used in the manufacture of vehicle bodies has continually increased. The zinc-coated steels currently used include hot-dip galvanized, galvanneal, electrozinc and electrozinc-iron coated steels. Such zinc coatings present problems relating to maintaining adequate pain adhesion.

Adhesion to zinc-coated steel, uncoated steel and aluminum substrates can be improved by providing a phosphate 11-.

lb 043.069 water run-off is then processed through a waste treatment system and the reduction in divalent metal ions removed at the rinse stage results in waste 043.069 conversion coating. To be effective in vehicle manufacturing applications, a conversion coating must be effective on uncoated steel, coated steel and aluminum substrates.

An improved zinc phosphate conversion coating for steel is disclosed'in U.S. Patent No. 4,330,345 to Miles et al. In the Miles patent, an alkali metal hydroxide is used to suppress hopeite crystal formation and encourage the formation of phosphophyllite [FeZn 2

(PO

4 2 crystals, or zinc-iron phosphate, on the surface of the steel panels. The phosphophyllite improves corrosion resistance by reducing the alkaline solubility of the coating. The alkaline solubility of the coating is reduced because iron ions from the surface of the steel panels are included with zinc in the conversion coating.

The formation of a zinc-iron crystal in a phosphate conversion coating is possible on steel substrates by providing a high ratio of alkali metal to zinc. The alkali metal suppresses the formation of hopeite crystals and allows the acid phosphate solution to draw iron ions from the surface of the substrate and bond to the iron ions in the boundary layer or reaction zone formed at the interface between the bath and the substrate. This technique for creating a phosphophyllite-rich phosphate conversion coating is not applicable to substrates which do not include iron ions.

The predominance of zinc-coated metal used in new vehicle designs interferes with the formation of phosphophyllite in accordance with the Miles patent. Generally, the zinc-coated panels do not provide an adequate source of iron ions to form phosphophyllite. It is not practical to form phosphophyllite crystals by adding of iron ions to the bath solution due to the tendency of the iron to precipitate from the solution causing unwanted sludge in the bath. A need exists for a phosphate conversion coating process for zinccoated substrates which yields a coating having reduced alkaline solubility.

i In U.S. patent No. 4,596,607 and Canadian patent No.

1,199,588 to Zurilla et al., a method of coating galvanized substrates to improve resistance to alkali corrosion attack is disclosed wherein high levels of nickel are incorporated into a zinc phosphate conversion coating solution. The Zurilla process uses high zinc and nickel levels in the zinc phosphating coating composition to achieve increased resistance to alkaline corrosion attack. The nickel concentration of the bath as disclosed in Zurilla is 85 to 94 mole percent of the total zinc-nickel divalent metal cations with a minimum of 0.2 grams per liter (200 ppm) zinc ion concentration in the bath solution. The extremely high levels of nickel and zinc disclosed in Zurilla result in high material costs on the order of three to five times the cost of prior zinc phosphate conversion coatings for steel. Also, the high zinc and nickel levels result in increased waste disposal problems since the zinc and nickel content of the phosphate coating composition results in i higher levels of such metals being dragged through to the water rinse stage following the coating stage. Reference i!s also made to U.S. patent No. 4,595,424.

20. It has also been proposed to include other divalent metal ions in phosphate conversion coatings such as manganese.

However, one problem with the use of manganese is that it is characterized by multiple valence states. In valence states other than the divalent state, manganese tends to oxidize and precipitate, forming a sludge in the bath instead of coating the substrate. The sludge must be filtered from the bath to prevent contamination of the surface.

A primary objective of the present invention is to increase the alkaline corrosion resistance of phosphate conversion coatings 30. applied to zinc-coated metals. By increasing the resistance of the phosphate coating to alkaline corrosion attack, it is anticipated that the ultimate objective of increasing corrosion reistance of vehicles to more than five years will be achieved.

i 1 j Another objective is to improve the control of the phosphate coating process so that an effective coating, which is both corrosion-resistant and U i 3a liic: Ir i 4 1 043.069 adhesion-promoting, can be consistently applied to steel, aluminum and zinc-coated panels. As part of this general objective, the control of a phosphate coating process including manganese is desired wherein sludge formation is minimized.

A further objective of the present invention is to reduce the quantity of metal ions transferred to a waste disposal system servicing the rinse stage of the phosphate conversion coating line. By reducing the quantity of metal ions transferred to waste disposal, the overall environmental impact of the process is minimized. Another important objective of the present invention is to provide a conversion coating which satisfies the above objectives while not unduly increasing the cost of the conversion cL ting process.

soa SUMMARY OF THE INVENTION o 0 as This invention relates to a method of forming a phosphate oo conversion coating on a metal substrate in which a coating composition, comprising zinc, another divalent cation such as nickel or manganese, and a non-coating, monovalent metal cation. The 'nvention improves the alkaline solubility of conversion coatings applied to ;inc-coated substrates and produces a coating having favorable crystal structuTe and good paint adhesion characteristics.

According to the method of the present invention, three essential components of the conversion coating bath are maintained within relative proportions to obtain a preferred crystal structure, referred to as "Phosphonicollite" [Zn 2 Ni(PO4) 2 3 or "Phosphomangollite" ([Zn 2 Mn(P0 4 2 which are considered trademarks of the assignee. A Phosphonicollite is a zinc-nickel phosphate which has superior alkaline solubility characteristics as compared to hopeite crystals characteristic of other phosphate conversion coatings, the essential constituents being grouped as follows: ~p 043.069 A potassium, sodium, or armnonium ions present as a phosphate; B zinc ions; and C nickel or nickel and manganese.

The quantity of zinc ions in the coating composition at bath dilution is between 300 ppm and 1000 ppm. The ratios in which the essential constituents may be combined may range broadly from 4-40 parts A two parts B 1-10 parts C. A preferred range of the ratios of essential ingredients is 8-20 parts A two parts B 2-3 parts C, with the preferred quantity of zinc being between 500 to 700 ppm.

Optimum performance has been achieved when the essential constituents are combined in the relative proportions of about 16 parts A: 2 parts B 3 parts C.

All references to parts are to be construed as parts by weight unless otherwise indicated.

The method is preferably performed by supplementing the essential constituents with accelerators, complexing agents, surfactants and the like and is initially prepared as a two-part concentrate as follows:

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*1 1.

2.

3.

4.

5.

6.

7.

8.

9.

Raw Material Water Phosphoric Acid (75%) Nitric Acid Zinc Oxide Nickel Oxide Sodium Hydroxide (50 Anxmonium Bifluoride Sodium salt of 2 ethy hexyl sulfate Nitro Benzene Sulfoni TABLE I CONCENTRATE A Most Preferred Prel Range Ran 20% 10 38% 20 21% 5- 5% 4- 8% 3- 4% 0- 2% 0.2 0.3% 0.2 c Acid trace 0ferred ge -50% -45% 25% 9% 18% 6% 2-5% 2-0.5% trace Broad Range 0-80% 10-60% 2-35% 2-15% 1.5-25% 0-10% 0-10% 0.1% 0-trace II i 043.069 TABLE II CONCENTRATE B Most Chemical Preferred Preferred Broad Raw Material Family Range Range Range 1. Water Solvent 34% 30-60% 30-80% 2. Phosphoric Acid Acid 28% 20-35% 10-35% 3. Nitric Acid Acid 5% 0-10% 0-15% 4. Zinc Dxide Alkali 13% 0-30% 0-30% 5. Nickel Oxide Alkali 20% 0-45% 0-45% i As used herein, all percentages are percent by weight and "trace" is about 0.05 to 0.1%.

According to the present invention, a phosphate coating bath comprising a substantially saturated solution of zinc, nickel and alkali metal or other monovalent non-coating ions results in the formation of a nickel-enriched S phosphate coating having improved alkaline solubility characteristics. The surprising result realized by the method of the present invention is that as the zinc concentration of the coating bath decreases, the nickel content of the resulting coating is increased without increasing the concentration of the nickel.

PThis surprising effect is particularly evident at higher nickel concentrations. If Smillion, the increase in nickel in the coating per unit of nickel added to the bath is less than in baths wherein the zinc concentration is in the range of 300 to 1000 parts per million.

6 I 1 I C While not wishing to be bound by theory, it is believed Lhat the inclusion of nickel in the coating depends on the relative proportion of nickel and other divalent metal ions available for precipitation on the metal surface. The inclusion of nickel in the coating may be controlled by controlling the concentration of the divalent metal ions at the boundary layer. The relative proportion of ions must be controlled since different divalent metal ions have different precipitation characteristics. At the boundary layer, the zinc concentration is higher than the zinc bath concentration by an amount which can be approximated by calculation from the nickel to zinc ratio in the bath and the t A rV

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Ur- $1 j 6a

I'

043.069 resultant coating composition. It has been determined that low zinc/high nickel phosphate coating solutions produce a higher nickel content in the phosphate coating than either high zinc/high nickel or low zinc/low nickel coating solutions.

According to another aspect of the present invention, a third divalent fietal ion may be added to the coating solution to further improve the alkaline solubility characteristics of the resulting coating. The third divalent metal ion is preferably manganese. When manganese is included in the bath, the nickel content of the coating drops because the presence of manganese in the i boundary layer competes with nickel for inclusion in the phosphate coating.

10. Manganese is considerably less expensive than nickel and therefore a 1i S« r manganese/nickel/zinc phosphate coating solution may be the most cost-effective S, method of improving resistance to alkaline solubility. Alkaline solubility of o 0 4 manganese/nickel/phosphate coatings is improved to the extent that the annonium dichromate stripping process generally used to strip phosphate coatings is ineffective to remove the manganese/nickel/zinc phosphate coating completely.

8t S4 t

S"

t Prior attempts to manufacture a manganese phosphate Sconcentrate encountered a serious problem of unwanted precipitation that formed sludge which is turn must be removed. Adding manganese alkali, such as MnO,

MN(OH)

2 or MnCO 3 to phosphoric acid results in the formation of a brownish sludge. According to the present invention, nitrogen-containing reducing agents such as sodium nitrite, hydrazine sulfate, or hydroxylamine sulfate eliminates the unwanted precipitation. The precise quantity of reducing agent required to eliminate precipitation depends upon the r .y of the manganese alkali. The reducing agent must be added prior to the manganese and prior to any oxidizer.

7 e i -I; 4 .4 BRIEF DESCRIPTION OF THE DRAWINGS Fibure 1 graphically represents data from Table IV relating the nickel content of a phosphate coating to the nickel concentration in the corresponding phosphate bath. Two types of phosphate baths are compared. One o *9 a a S eROS *0 a 0 .4 .4.404 .4 .4, *0 .4 4 .4.4 a 0 0 .4 05 '9a 0 0*0 o a a a .4.

.4.4 .4 .4.4 .4 9.

.4.04*a .4 0 .4 a., 7a

TESTING

I 111 3 1 rI 043.069 has low zinc levels and the other has high zinc levels. The coatings are applied to steel panels such as used by the automotive industry for body panels.

Figure 2 graphically presents test data as in Figure 1 as applied to hot-dip galvanized panels.

Figure 3 graphically presents test data as in Figure 1 as applied to electrozinc panels.

Figure 4 graphically presents test data as in Figure 1 as applied to galvanneal panels.

Figure 5 graphically presents test data as in Figure 1 as applied J1 0 to electrozinc-iron panels.

*4 o r Figure 6 graphically presents test data from Tables V and VII relating the ratio of nickel to zinc in the boundary layer to the percentage of nickel in the coating as applied to steel panels.

9 9 Figure 7 graphically presents test data as in Figure 6 as applied to hot-dip galvanized panels.

S Figure 8 graphically presents test data as in Figure 6 as applied to electrozinc panels.

Figure 9 graphically presents test data as in Figure 6 as applied to galvanneal panels.

Figure 10 graphically presents test data as in Figure 6 as applied to electrozine-iron panels.

l 0 I L i i-

III-

043.069 Figure 11 graphically presents test data showing the improvement in alkaline solubility realized by increasing the nickel concentration in a phosphate bath as applied to steel panels.

Figure 12 graphically presents test data as in Figure 11 as applied to- hot-dip galvanized panels.

Figure 13 graphically presents test data as in Figure 11 as applied to electrozinc panels.

Figure 14 graphically presents test data as in Figure 11 as 2 applied to galvanneal panels.

Du °%lJ0. Figure 15 graphically presents test data as in Figure 11 as o* o applied to electrozinc-iron panels.

D 0 Figure 16 graphically presents the dependence of corrosion and oo .00 paint adhesion on the nickel to zinc ratio in the boundary layer as applied to steel O a panels.

C'

oo o Figure 17 graphically presents test data as in Figure 16 as O° applied to hot-dip galvanized panels.

o 0 Figure 18 graphically presents test data as in Figure 16 as applied to electrozine panels.

Figure 19 graphically presents test data as in Figure 16 as applied to galvanneal panels.

Figure 20 graphically presents test data as in Figure 16 as applied to electrozinc-iron panels.

-9r~ 043.069 The above examDles were tested for corrosion resistance and

I

043.069 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention is generally referred to as phosphate conversion coating wherein a zinc phosphate solution is applied to metal substrates by spray or irnersion. The metal substrate is first cleaned with an aqueous alkaline cleaner solution. The cleaner may include or be followed by a water rinse containing a titanium conditioning compound. The cleaned and conditioned metal substrate is then sprayed or immersed in the phosphate bath solution of the present invention which 'is preferably maintained at a temperature between about 1000 to 1400 F. The phosphate coating solution preferably has a total acid content of between about 10 and 30 points and a free acid content of between about 0.5 and 1.0 points. The total acid to free acid ratio is preferably between about 10:1 and 60:1. The pH of the solution is preferably maintained between 2.5 and 3.5. Nitrites may be present in the bath in the amount of about to about 2.5 points.

Following application of the phosphate solution, the metal substrate is rinsed with water at ambient temperature to about 1000 F for about one minute. The metal substrate is then treated with a sealer comprising a chromate or chromic acid-based corrosion inhibiting sealer at a temperature of between ambient and 1200 F for about one minute which is followed by a deionized i water rinse at ambient temperature for about thirty seconds.

10 -i i LII ^v w r f- c -w ii~irli~ll....11 1i1 i'iaaf a 4.

One benefit realized according to the present invention over high zinc phosphate baths is a reduction of the quantity of divalent metal ions transferred from the phosphate treatment step to the water rinse. A quantity of phosphating solution is normally trapped in openings in treated objects, such as vehicle bodies. The trapped phosphating solution is preferably drained off at the rinse stage. According to the present invention, the total quantity of divalent metal ions is reduced, as compared to high zinc phosphate baths, by reducing the concentration of zinc ions.

As the concentration is reduced, the total quantity of ions transferred from the phosphate stage to the rinse stage is reduced. The

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.1 '1 043.069 Again, the percentage of nickel in the phosphate coating is increased most effectively by the use of the low zinc/high nickel formulations such 043.069 water run-off is then processed through a waste treatment system and the reduction in divalent metal ions removed at the rinse stage results in waste treatment savings.

The primary thrust of the present invention is an improvement in the coating step of the above process.

EXAMPLES

EXAMPLE 1 A phosphating bath solution was prepared from two concentrates 4 t I r t 4 ftrt as follows:

CONCENTRATE

Al

CONCENTRATE

B Name of Raw Material Water Phosphoric Acid (75%) SNitric Acid (67%) Zinc Oxide Nickel Oxide o. 15. Sodium Hydroxide (50%) Potassium Hydroxide (45%) Sodium Salt of 2 Ethyl S Hexyl Sulfate Amnonium Bifluoride Ammonium Hydroxide Nitro Benzene Sulfonic Acid 29% 36% 18% 10% 4% 34% 28% 13% 1% 2% <0.1% <0.1% LiJ 11 i i The above concentrates were diluted to bath concentration by adding 5 liters of concentrate Al to 378.5 liters of water, to which was added a mixture of 10 liters of Concentrate B combined with 378.5 liters of water. The above concentrates after dilution, were combined and a sodium nitrite solution comprising 50 grams sodium nitrate in 3478.5 liters of water which is added to the concentrate as an accelerator. The coating was spray-applied for to 120 second or immersion-applied for 90 to 300 seconds in a temperature of 115-130° F. When no B concentrate is used, a total of 7 liters of concentrate is added to 378.5 liters of water.

All the rest of the procedure is the same_ 00 0 0000 00 004 ,o O 0 .00 *r 00 *0r 00004 4;" lla 043.069 Using this equation, nickel/zinc ratios in the boundary layers are calculated with the results shown in Table VII below: 043.069 The use of alkali metal phosphate in preparation of a zinc phosphate bath involves addition of a less acidic alkali metal phosphate concentrate to a more acidic bath prepared from a standard zinc phosphate concentrate. The higher pH of the alkali metal phosphate concentrate will cause precipitation of zinc phosphate during periods of inadequate mixing. The phosphate bath will have a lower zinc concentration when the alkali metal phosphate is added at a faster rate than when it is added at a slower rate.

Variation in degree of precipitation will affect the free acid in that more precipitation will lead to higher free acid. Examples 7, 7a, 12 and 12a demonstrate that one concentrate can produce baths that react differently.

EXAMPLES 2-16 The following examples have been prepared in accordance with I't the method described in Example 1 above. Examples 3, 4 and 11 are control examples having a high zinc concentration which does not include Concentrate B, a 15. source of alkali metal ions.

Examples including manganese are prepared by adding the specified quantity of the nitrogen-containing reducing agent to a phosphoric acid/water mixture. To this solution, a manganese-containing alkali, such as MnO, Mn(OH) 2 and Mn(C0 3 is added. If an oxidizer, such as nitric acid, added to the bath, it is added subsequent to the addition of the manganese-containing alkali.

Examples 2 through 16 were prepared in accordance with Example 1 above. However, the coating compositions were changed in accordance with the following tables: -12- 043.069 043.069 EXAMPLE 2 Name of Raw Material Water Phosphoric Acid (75%) Nitric Acid (67%) Zinc Oxide Nickel Oxide Sodium Hydroxide (50%) Potassium Hydroxide (45%) Sodium Salt of 2 Ethyl Hexyl Sulfate Ammonium Bifluoride Anmonium Hydroxide Nitro Benzene Sulfonic Acid

CONCENTRATE

A2 35% 39% 12% 5% 4% 2%

CONCENTRATE

B

34% 28% 13% <1% 2% 0.1% 0.1% EXAMPLE 3 Name of Raw Material 0 a a 2000 *25 o ag D0:$ 0 B 00 *n 00 0 00t; 00 0 0::a Water Phosphoric Acid (75%) Nitric Acid (67%) Zinc Oxide Nickel Oxide Sodium Hydroxide Potassium Hydroxide Sodium Salt of 2 Ethyl Hexyl Sulfate Ammonium Bifluoride Amnonium Hydroxide Nitro Benzene Sulfonic Acid

CONCENTRATE

A3 29% 39% 11% 3% <1% 2% <0.1% <0.1% EXAMPLE 4

CONCENTRATE

A4

CONCENTRATE

B Name of Raw Material 00. 0 to o 0 0R o to Water Phosphoric Acid (75%) Nitric Acid (67%) Zinc Oxide Nickel Oxide Sodium Hydroxide (50%) Potassium Hydroxide (45%) Sodium Salt of 2 Ethyl Hexyl Sulfate Amnonium Bifluoride Amnnonium Hydroxide Nitro Benzene Sulfonic Acid 24% 35% 23% 10% 34% 28% 13% <1% 2% 0.1% (0.1% -13i rORROSTN AND ADHESION TEST RESULTS 'i 043.069 EXAMPLE Name of Raw Material

CONCENTRATE

A5

CONCENTRATE

B

Water Phosphoric Acid (75%) Nitric Acid (67%) Zinc Oxide Nickel Oxide Sodium Hydroxide (50%) Potassium Hydroxide (45%) Sodium Salt of 2 Ethyl Hexyl Sulfate Amnonium Bifluoride Anrnonium Hydroxide Nitro Benzene Sulfonic Acid 20% 39% 21% 5% 8% 4% 34% 28% 13% <1% 2% <0.1% 0.1% EXAMPLE 6 Name of Raw Material

CONCENTRATE

A6

CONCENTRATE

B

2 i t it

I,

0ft 4v 4 Water Phosphoric Acid (75%) Nitric Acid (67%) Zinc Oxide Nickel Oxide Sodium Hydroxide (50%) Potassium Hydroxide (45%) Sodium Salt of 2 Ethyl Hexyl Sulfate Ammonium Bifluoride Ammonium Hydroxide Nitro Benzene Sulfonic Acid 31% 36% 17% 4% 9% 1% 34% 28% 13% <1% 1% 0.1% <0.1% EXAMPLE 7

CONCENTRATE

A7

CONCENTRATE

B

Name of Raw Material tL I 43'5~.

34 t :340.

Water Phosphoric Acid (75%) Nitric Acid (67%) Zinc Oxide Nickel Oxide Sodium Hydroxide (50%) Potassium Hydroxide (45%) Sodium Salt of 2 Ethyl Hexyl Sulfate Amnonium Bifluoride Anrnonium Hydroxide Nitro Benzene Sulfonic Acid 35% 38% 12% 4% 6% 3% 34% 28% m-- 13% 1% 1% <0.1% 0.1% -14- TtJ- 1 043.069 TABLE IX 140* F Indoor Scab Test Results Type of Phosphate Low Zinc Low Zinc Low Zinc Low Zinc High Zinc Low Nickel High Nickel High Nickel High Nickel ligh Nickel 043.069 EXAMPLE 8 CONCENTRATE CONCENTRATE Name of Raw Material A8 B Water 36% 34% Phosphoric Acid 39% 28% Nitric Acid 10% Zinc Oxide 5% Nickel Oxide 5% Sodium Hydroxide 3% 13% Potassium Hydroxide Sodium Salt of 2 Ethyl Hexyl Sulfate 1% Arrnonium Bifluoride 1% Ammonium Hydroxide <0.1% Nitro Benzene Sulfonic Acid <0.1% EXAMPLE 9

CONCENTRATE

Name of Raw Material A9 Water 2P Phosphoric Acid 33% Nitric Acid 16% Zinc Oxide 8% Sae Nickel Oxide 4% Sodium Hydroxide Potassium Hydroxide Sodium Salt of 2 Ethyl Hexyl Sulfate 1% Ammonium Bifluoride 1% Anmmonium Hydroxide <0.1% 30 f Nitro Benzene Sulfonic Acid 0.1% 0 a« EXAMPLE CONCENTRATE CONCENTRATE Name of Raw Material A9 B SWater 35% 34% Phosphoric Acid 33% 28% o, Nitric Acid 16% Zinc Oxide 8% Nickel Oxide 4% Sodium Hydroxide 13% Potassium Hydroxide Sodium Salt of-2 Ethyl Hexyl Sulfate 1% Amnonium Bifluoride 1% Amnonium Hydroxide 0.1% Nitro Benzene Sulfonic Acid 0.1% L I II I I I I 043.069 EXAMPLE 11

CONCENTRATE

Name of Raw Material Water 36% Phosphoric Acid 39% Nitric Acid 11% Zinc Oxide 11% Nickel Oxide 1% Sodium Hydroxide Potassium Hydroxide Sodium Salt of 2 Ethyl Hexyl Sulfate <1% Ammonium Bifluoride 1% Anmonium Hydroxide 0.1% Nitro Benzene Sulfonic Acid <0.1% EXAMPLE 12 CONCENTRATE CONCENTRATE Name of Raw Material A10 B Water 36% 34% Phosphoric Acid 39% 28% Nitric Acid 11% Zinc Oxide 11% Nickel Oxide 1% Sodium Hydroxide 13% Potassium Hydroxide Sodium Salt of 2 Ethyl Hexyl Sulfate 1% Amnonium Bifluoride 1% Ammonium Hydroxide <0.1% Nitro Benzene Sulfonic Acid 0.1% EXAMPLE 13 CONCENTRATE CONCENTRATE Name of Raw Material All B Water 37% 34% Phosphoric Acid 39% 28% Nitric Acid 11% Zinc Oxide 11% Nickel Oxide 1% Sodium Hydroxide 13% Potassium Hydroxide Sodium Salt of 2 Ethyl Hexyl Sulfate 1% Amnmonium Bifluoride Ammonium Hydroxide <0.1% Nitro Benzene Sulfonic Acid 0.1% -16- 4, I i rl i Name of Raw Material Water Phosphoric Acid (75%) Nitric Acid (67%) Zinc Oxide Nickel Oxide Sodium Hydroxide (50%) Potassium Hydroxide (45%) Sodium Salt of 2 Ethyl Hexyl Sulfate Amnonium Bifluoride Amnonium Hydroxide Nitro Benzene Sulfonic Acid

CONCENTRATE

A12 35% 33% 16% 8% 4%

CONCENTRATE

B

34% 28% 13% <1% <0.1% <0.1% 25.

309.

o *9 9F 9* p .9 As the bath is used on a cormrercial basis, the phosphate bath is replenished after a series of coatings. The bath will become enriched with nickel after a series of coatings because more zinc than nickel is contained in the phosphate coating. The replenishment solution should be formulated to maintain the desired monovalent metal ion to zinc ion to nickel ion concentration.

The above examples, when diluted to bath concentration, yield the following approximate ratios of alkali metal to zinc to nickel ions: Exarrle No.

1 2 3 4 6 7 8 9 11 12 12a TABLE III Alkali Metal Ion: Zinc Ion: Nickel Ion Ratio Table 4.5:1:0.80 4.9:1:0.92 0.1:1:0.30 5.2:1:0.97 7.8:1:1.24 6.0:1:1.39 6.4:1:1.35 5.8:1:0.88 0.1:1:0.57 0.1:1:0.20 5.0:1:0.27 9.4:1:0.55 17 -i I 043.069 In the following section, this data will be related to the solubility of the phosphate coating in alkaline media.

ALKALINE SOLUBILITIES OF PHOSPHATE COATINGS 043 .069 EXAMPLE CONC ENTRATE CONCENTRATE Name of Raw Material Ml MB 'Water 2996 34% Phosphoric Acid 36% 28% Nitric Acid 19% Zinc Oxide Nickel Oxide 1% Manganese Oxide 4% 1. Sodium Flydroxide 13% Potassium Hydroxide 7- 19% Hydroxylamine Sulfate Sodium Salt of 2 Ethyl Hexyl Sulfate Am~onium Bifluoride 1% Arrmonium Hydroxide 0.1% Nitro Benzene Sulfonic Acid 0.1% EXAMPLE 16 CONCENTRATE CONCENTRATE Name of Raw Material M2 MB Water 24% 34% Phosphoric Acid 36% 28% Nitric Acid 23% Zinc Oxide 9% Nickel Oxide 3% Manganese Oxide 4% SSodium Hydroxide 13% Potassium Hydroxide (4 5%)19 Hydroxylan-ine Sulfate 1% Sc-iiium 3!alt of 2 Ethyl Hexyl Sulfate 1% Anynonium Bifluoride 1% 3'Arrnionium Hydroxide Nitro Benzene Sulfonic Acid (0.1% i c I

I

t8 4 E 0 8 I tii

TESTING

A series of test panels were coated with combinations of two-part coating solutions. The test panels included uncoated steel panels, hot-dip galvanized, electrozinc, galvanneal, and electrozinc-iron. The test panels were processed in a laboratory by alkaline cleaning, conditioning, phosphate coating, rinsing, sealing and rinsing to simulate the previously described manufacturing process. The panels were dried and painted with a cationic electrocoat primer paint. The panels were scribed with either an X or a straight line and then subjected to four different testing procedures, the General Motors Scab Cycle (GSC), Ford Scab Cycle (FSC), Automatic Scab Cycle (ASC), Florida Exposure Test, and the outdoor Scab Cycle (OSC).

TEST METHODS The GSC, or 140 F indoor scab test, is a four-week test with each week of testing consisting of five twenty-four hour cycles comprising immersion in a 5% sodium chloride solution at room temperature followed by a 75 minute drying cycle at room temperature followed by 22.5 hours at 85% relative humidity at 20. 140°F. The panels are maintained at 140'F at 85% relative humidity over the two-day period to complete the week. Prior to testing, the test panels are scribed with a carbide-tipped scribing tool. After the testing cycle is complete, the scribe is evaluated by simultaneously scraping the paint and blowing with an air gun.

25. The test results were reported as rated from 0, indicating a total paint loss, to 5, indicating no paint loss.

The FSC test is the same as the GSC test except the test is for ten weeks, the temperature during the humidity exposure portion of the test is set at 120" F and the scribe is evaluated by applying Scotch Brand 898 tape and removing it and rating as above.

-19- .4 *8 4 81c r 4 *a 4 44 4 4 8 8.

888 1 2 i to electrozinc-iron panels.

043.069 The ASC test is comprisd of 98 twelve hour cycles wherein each cycle consists of a four and three-quarter hour 95 to 1000 humidity exposure followed by a 15 minute salt fog followed by seven hours of low humidity (less than percent humidity) drying at 1200 F. The ASC test is evaluated in the same way as the FSC test.

The Florida exposure test is a three-month outdoor exposure facing the south and oriented at 5 from horizontal at an inland site in Florida. A salt mist is applied to the test panels twice a week. Panels are scribed per ASTM D-1654 prior to exposure and soaked in water for 72 hours following exposure.

The panels are crosshatched after soaking and tested according to ASTM D-3359, Method B.

The most reliable test is the OSC test wherein a six-inch scribe is made on one-half of a panel and the other half is preconditioned in a gravelometer in accordance with SAE J 400. The panel is then exposed to salt spray for twenty-four hours which is followed by deionized water immersion for forty-eight hours. The panel is then placed outside at a forty-five degree angle southern exposure. A steel control panel, treated with the same conversion process except for the final rinse which was chrome (III) final rinse, is treated simultaneously in the same manner. When the control panel exhibits a corrosion scab of about six millimeters, the panels are soaked for twenty-four hours. The OSC is evaluated according to the same procedure used for the FSC and ASC tests as described previously.

g The panels scribed with a crosshatch grid were used to evaluate adhesion performance. After cyclical testing, the panels were contacted by an adhesive tape which is removed and qualitatively evaluated depending upon the degree of removal of non-adhering film by the tape. The numerical rating for this test is based upon a five-point scale ranging from a rating of 0 for no adhesion to for perfect adhesion.

applied to electrozinc -iron panels.

043.069 The above examples were tested for corrosion resistance and adhesion by the above-described test method.

Table IV shows the relationship of the percentages of nickel in the baths, the zinc level in the baths, and the percentage of nickel contained in the coatings for six different phosphate bath compositions as applied to steel, hotdip galvanized, electrozinc, galvanneal, and electrozinc-iron by both the spray and hrmiersion methods.

It 4 Type of Phosphate Concentrate Used Nickel oncentration Spray Phosphate Steel Hot Dip Galvanized Electrozino AGl Galvanneal Electrozino-Iron Imme~rsion Phosphate Steel Hot Dip Galvanized Electrozine AOI Gaivanneal Electrozinc-tron Low Zinc Low Nickel Example 12 208 ppm 0.71% 0.78% 0.49% 0.59% 0.62% 0.53% 1.15% 1.01% 1.2 7% 1.18% Percentage of Low Zinc High Nickel Example 1 670 ppm 1.89% 1.42% 1.39% 1.431% 1.36% 1.5 6% 2.10% 1.80% 2.3 4% 1.97% TABLE IV Nickel In Phosphate Coatings Low Zinc Low Zinc High Nickel High Nickel Examp~le 2 Example 4 708 ppm 88O ppm 1.8 1% 1E.49% 1.69% 1.39% 2.10% 1.98% 2.33% 2.1296 2.41% 1.67% 1.49% 1.76% 1.52% 2.12% 2.2 3% 2.2 3% 2.59% 2.16% High Zinc Low Nickel Examp~le 11 250 ppm 0.3B8% 0.41% 0.3 6% 0.40% 0.40% 0.4 3% 0.8 2% 0.64% 0.68% 0.73% High Zinc High Nickel Examp~le 3 635 ppm 0.86% 0.7 3% 0.64% 0.7 4% 0.64% 1.05% 1.20% 0.87% 1.03% 0.75% I I I. 1>1.

Li I i i ii 043.069 Referring to the above table, examples that are low zinc/high nickel phosphates yield the highest percentage of nickel in the phosphate coatings.

Example 11, which is a low zinc/low nickel phosphate, has a lower percentage of nickel incorporated in the phosphate coating. Even lower levels of nickel incorporation are achieved when a high zinc/low nickel composition is used as shown in Example 10. The use of a high zinc/high nickel phosphate bath results in only slightly more nickel in the phosphate coating than in the low zinc/low nickel bath and considerably less than any of the low zinc/high nickel baths. Thus, to obtain more nickel in the coating, the bath concentration of nickel should be high and the bath concentration of zinc should be low. The results are graphically presented in Figures 1-5 which clearly show that with either immersion or spray application methods, the low zinc formulations are more efficient in increasing nickel content of the phosphate coating than high zinc formulations. Figures each relate to a different substrate material and the results ahcieved indicate that the low zinc formulations are preferable for all substrates.

For each of the above examples, the percentage of nickel in the phosphate coatings is shown in Table V below for the five tested substrates after immersion phosphating.

Concentrates Used Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 7a Example I Example 6 Example 11 Example 12 Example 12a Immerslon Phosphate Steel 1.56% 1.05% 2.12% 1.72% 2.79% 2.65% 2.69% 1.66% 1.56% 0.43% 0.53% 0.59% TABLE V Percentage of Nickel In Phosphate Coatings* Hot Dip Galvanized Electrozne 2.10% 1.80% 2.10% 1.98% 1.20% 0.87% 2.23% 2,,23% 2.36% 2.51% 3.15% 3.33% 3.29% 2.69% 3.89% 3.58% 3.03% 2.61% 2.36% 1.68% 0.82% 0.64% 1.15% 1.01% 1.15% 0.98% A01 Galvanneel 2.34% 2.33% 1.03% 2.59% 3.04% 3.47% S3.13% 4.23% 2.51% 1.74% 0.68% 1.27% 1.18% Electro- Zinc-Iron 1.97% 2.12% 0.75% 2.16% 2.47% 3.29% 2.45% 3.93% 2.01% 1.62% 0.73% 1.18% 1.05% -22- 7- -1- 043.069 TABLE XVIII _r i 1 i i i i i II I I 043.069 Again, the percentage of nickel in the phosphate coating is increased most effectively by the use of the low zinc/high nickel formulations such as Examples 1, 2, 4, 5, 6, 7, 7a and 8. The low nickel/high zinc is the least effective and the low nickel/low zinc or the high nickel/high zinc are only slightly more effective.

NICKEL/ZINC RATIO IN THE BOUNDARY LAYER .2 0 0400 0b 0 40 Oa 0 0a @0 0 00 0 r.

a.r *0 0 00 i rI r 2b.

The proportion of nickel in the phosphate coating is proportional to the nickel/zinc ratio available for precipitation. Unfortunately, the ratio available for precipitation is not the overall bath ratio but rather the ratio at the boundary layer between the metal surface and the bulk of the bath. For all substrates tested high metal ion concentration in the boundary layer resulting from acid attack on the metal surface tended to lower the proportion of nickel available for precipitation. While it is not practical to measure metal ion concentrations at the boundry layer directly, the boundary layer concentrations can be calculated based on the linear correlation between the proportion of nickel in the coating and the nickel/zinc ratio. As the zinc concentration increases, the linear correlation coefficient is maximized at the boundary layer concentration. Furthermore, as the concentration of zinc is increased, the y-intercept should approach zero. These two criteria will be met only half the time each for application of this change to random data. Whether they follow the expected changes or not constitutes a test of the accuracy of the theory. For both criteria to be met for all five materials there is a 99.9% chance that the theory is correct. In fact, all five materials met these criteria. The increase in metal ions in the boundary layer and the correlation coefficients are given in Table VI.

-23- 0 043.069 TABLE XIX EFFECT OF MANGANESE: PHOSPHORIC ACID RATIO Example Example Example Example Mar -I D c i -i rr 043.069 TABLE VI Difference Between Bath and Boundary Layer Zinc Concentrations Extra Metal Ions At Bath Metal Substrate In the Boundnry Lsyer Concentration Steel 1600 ppm 0.906 Hot Dip Galvanized 450 ppm 0.913 Electrozlne 300 ppm 0.954 A01 Galvanneal 200 ppm 0.976 Electrozinc-ron 250 ppm 0.946 SCorrelation between percentage nickel in the phosphate coating and nickel to zinc ratio.

Immersion Phosphate Correlation Coefficient* At Boundary Layer Concentration 0.989 0.933 0.966 0.982 0.954 4 a *5 at a a 4J a a 4 *c a 54 5 a a s- For hot-dip galvanized and electrozinc, the extra metal ions are zinc and hence can be added directly to the zinc concentration in the bath to obtain the zinc concentration in the boundary layer. However, for steel, the increase in concentration reflects an increase in the iron concentration. Since iron ions have a greater tendency to cause precipitation, the concentration of additional metal ions in the boundary layer of 1600 ppm is somewhat distorted.

The ferrous ions compete more effectively than zinc ions for inclusion in the coating because phosphophyllite has a lower acid solubility than hopeite. This means that the determined concentration increase of 1600 ppm is greater than the actual ferrous ion concentration. The 1600 ppm represents the amount of zinc that would compete as effectively as the ferrous ions actually present and therefore can also be added directly to the bath concentration of zinc. A similar argument can be made for galvanneal and electrozinc-iron. The boundary layer ratios can be calculated by the following equation: ,.1 Nickel/zinc ratio In the boundary layer Nickel in Bath (Zinc in bath Extra metal ions in the boundary layer) -24- Si.- N fl'-~-,UTh~g~t'Th<,5L~Nt' na :A~LJ' qui~ 4 1 i :i i i ii i I i i I I i

I

043.069 Using this equation, nickel/zinc ratios in the boundary layers are calculated with the results shown in Table VII below: Concentrates Used Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 7a Example 8 Example 9 Example 11 Example 12 Example 12a Immerslon Phosphate TABLE VII Nickel/Zinc Ratio In the Boundary Layer* Hot Dip Galvanized Electrozlnc 0.524 0.592 0.596 0.682 0.246 0.260 0.578 0.641 0.668 0.790 0.824 0.954 0.784 0.912 0.894 1.063 0.532 0.613 0.419 0.459 0.147 0.161 0.164 0.186 0.262 0.317 A01 Galvanneal 0.649 0.755 0.271 0.691 0.899 1.063 1.023 1.217 0.682 0.490 0.172 0.204 0.369 Electro- Zinc-iron 0.619 0.717 0.266 0.665 0.841 1.017 0.964 1.135 0.646 0.474 0.167 0.195 0.341 I I t4 4 *0 C .sf Ie I t LI Figures 6-10 show the correlation between the nickel/zinc ratio in the boundary layer and the percentage nickel in the coating.

FORMATION OF PHOSPHOPHYLLITE WITH A HIGH NICKEL PHOSPHATE It has been previously established that higher phosphophyllite phosphate coating improves the painted corrosion resistance and paint adhesion on steel. In the previous section, it was shown that nickel competes with zinc for inclusion in the phosphate coating. It is critical to this invention that the inclusion of high phosphophyllite on iron-containing substrates is maintained at the high levels obtained with low zinc/low nickel baths. Data in Table VIII below shows that high nickel/low zinc phosphates have a phosphophyllite content equivalent to that of low nickel/low zinc phosphates. Notice that high zinc baths have lower phosphophyllite contents than the low zinc baths, even for the zinciron alloys, A01 galvanneal and electrozinc-iron. This will have important repercussions in the painted corrosion testing of these baths.

-1 -12- 043.069 Type of Phosphate Concentrate Used Nickel Concentration Spray Phosphate Steel ADI Osivanized Eiectrozinc-iron Immersion Phosphete Steel A01 Galvanneal Electrozinc-Iron TABLE VIII Percentage of Nickel In Phosphate Coatings Low Zinc Low Zinc Low Zinc Low Zinc High Zinc Hi11gh Zinc Low Nickel Hiigh~ Nickel High Nickel High Nickel Low Nickel High Nickel Examiple 12 Examp~le 1 Example 2 Examplie 4 Examrple 11 Examlrpe 3 20B ppm 670 ppm 708 ppm 380 ppm 250 ppm635pp 0.73% 0.02% 0.05% 1.00% 0.02% 0.09% 0.43% 0.03% 0.07% 1.00% 0.0 5% 0.08% 0.70% 0.02% 0.06% 0.03% 0.07% 0.85% 0.04% 0.04% 0.9 5% 0.04% 0.06% 0.4 1% 0.02% 0.03% 1.00% 0.02% 0.0 5% 0.32% 0.01% 0.03% 0.30% 0.02% 0.03% I t t t 1~ t fZ~ t OP-ratio a Phosphophyllite) (Hopeite Phosphophylte) t t 4 C f (C 26 CORROSION AND ADHESION TEST RESULTS INDOOR SCAB TEST RESULTS Table IX below shows the 140*F indoor scab test results on five substrates with spray and immersion application processes.

The low Zinc/high nickel baths show improved corrosion and adhesion results when applied by the immersion process. The adhesion and corrosion test results are superior for Examples 1, 2 and 4 as compared to the high zinc/high nickel composition of Example 3 and the low zinc/low nickel composition of Example 12 for electrozinc and hot-dip galvanized. This difference is ascribed to the higher nickel content. Steel, A01 galvanneal and electrozinc-iron showed worse performance with Example 3 only.

This difference can be ascribed to lower phosphophyllite contents.

r it

C,

tI t S t t t. C j 26a 1 I- said aqueous bath having a zinc ion concentration of between -14- 043. 069 TABLE IX 140' F Indoor Scab Test Results Low Zinc Low Zinc Low Zinc Low Zinc Iligh Zinc Low Nickel High Nickel lligh Nickel High Nickel High Nickel

I

I

I

ii ii ii 7 ir 4 10.

15.

Type of Phosphate Concentrates Used Nickel Concentration Spray Phosphate Steel Not Dip Galvanized Electrozinc A0l Gaivanneal Elec trozinc-liron Imsmersion Phosphate Steel Hot Dip Galvanized Electrozinc A01 Galvanneal Electrozinc-lron Example 12 20B ppm S Q'bCoss W Hatch Examrple 1 670 ppm S OlpCoss n) Hatch Examrple 2 708 ppm Sqrib0 Cocss (mmhi Hatch) Example 4 880 ppm S7rib~ Cross Example 3 635 ppm Hatc In Table X below, samples are shown. The automatic the automatic scab test results for the same scab test shows improvement in corrosion resistance with high nickel/low zinc baths as compared to the other two for hot-dip galvanized and electrozinc. Steel and electrozinc -iron show decreased performance form the high zinc bath, undoubtedly because of lower phosphophyllite.

On galvanneal, paint adhesion is adversely affected by high zinc baths but low nickel levels adversely affect corrosion resistance for all coated samples and equivalent results with uncoated steel. Variations from the general trend are believed to be unrelated to the expected effectiveness of the low zinc/high nickel compositions.

Type of Phosphate Concentrates Used Nickel Concentration Spray Phosphate Steel Hot Dip Galvanized Electrozinc A01 Galvanneal Electrozine-fron Immersion Phosphate Steel Hot Dip Galvanized Electrazinc A01 Galvanneal Electrozinc-fron Low Zinc Low Nickel Example 12 208 ppm S4 rbT Cross m) Hatch TABLE X Automatic Scab Test Results Low Zinc Low Zinc Low Zinc High Nickel High Nickel High Nickel Example 1 Example 2 Example 4 670 pprn 708 pprn 880 ppm Slb Cross Crlb oss Srlbe Cross MM Hth l )l Hatch Wf~l Hatch hifgh. Zinc High Nickel Example 3 635 ppm gribp Cross (mn) Hatch -27- It 4 Now.

043.069 A second automatic scab test was conducted for Examples 5-9 and 12a as shown in Table XI below. The test results showed improvement in adhesion for galvanneal and elec trozinc -iron substrates for the low zinc/high nickel comp~ositions as compared to the low zinc/l1ow nickel and high zinc/high nickel con-positions. The corrosion test results indicated substantial improvemnent for hot-dip galvanized and electrozinc with the low zinc/high nickel formulations.

Steel showed slight improvement with high nickel baths. The results of this test will be discussed in more detail in the section on alkaline solubility.

S St t

V

I

*1S (.5 a 4.55,

S

St F C

C

t (4 Tyjpe of Phosphate Low Zinc Low Nickel Concentrates Used Example 12a S Orlb Coss Hatch Steel 6am 5 Hot Dip Galvanized 6mm 4 Electrozinc 2mn S AOl Galvanneal 2am 4+ Electrozlnc-Iron 2am 2 0 mmersion Phosphate TABLE Xl Automatic Scab Test Results* Low Zinc Low Zinc Low Zinc High Nickel High Nickel High Nickel Example 5 Examp~le 6 ExanVle 7 nT Coss, S7rlbT Cross, Sqrlb Cross Hatch am Hatch (mmJ Hatch 4rnn S 4am~ 4+ 4am 5 3amr 4+ 2rnm 5 3am 4+ 5g 5 4am 5 4ram 5 2am 3 laM S 2anm 4+ igh Zinc High Nickel Example 8 S7rbi Coss Hatch 4am 5 4asrn 4+ IMF 5 3mrn 5 2am 4 High zinc High Nickel Examp~le 9 S~rlb Cross .1n Hatch Sra Sam 4+ lam S lam 3 lain 3 12 Examples 1-4 and Xt, A were tested in Florida exposure with the results shown in Table XII below.

4 I

A

Armmnniijm Rifhinriria 9 0/ 043.069 TABLE XII Florida Exposure Test Results Type of Phosphate Low Zinc Low Zinc Low Zinc Low Zinc Hligh Zinc Low Nickel High Nickel High Nickel High Nickel High Nickel Concentrates Used Example 12 Exarple 1 Example 2 Examnple 4 Examnple 3 Nickel Concentration 208 ppmn 670 ppm 708 ppm 880 ppm 635 ppmn S~ribc Cross S ribp Cross S ribp Cross Eribe Cross Scribe Cross nmI Hatch rn)_ [latch Hatch In Hatch W rnn) Hach Sray Phosphate Steel 3rnmn 5 3pm 5 2pmr 5 2ir.m 5 Spin 2 Hlotfip Galvanized Sn-e 2+ 2mmy 3 On-sn 4 iOM- 4 3nyrn 3 Electrozinc IMn 2+ 3pmn 3 Onson 4 0nMm 4 IMm 3 A01 Galvanneal On-n 3 iO-n 3+ iOn-n 4+ Ornm 4+ 0MM 2+ Electrozins-Iron &msn 4 iOn-n 4 (kim 4+ (On-n 4+ 9nwn 1 Imnersion Phosphate Steel 2rn 5 2nmm 5 2pmy 5 Pawrn 5 2na Hot Dip Galvanized Den-n 4 (On-n 4+ 0MM 4+ OMn- 4 en-n 4 Eiectrozlnc Ornm 4 On-r 4 (krnm 4 Onsn 4 On-sn 2+ A01 Galvanneal Ornm 4 (OM- 4+ (kern 4+ (On-n 5 (On-n 3 Ele ctrozlnc-lIron heM 3 (OM- 4 (kem 4 In-e 3 IM-r 3 Z The Florida exposure test results show increased corrosion resistance or paint adhesion of the low zinc/high nickel composition on electrozinc, '20:4- galvanneal and hot-dip galvanized when compared to the low zinc/low nickel or high zinc/high nickel compositions. Superior corrosion resistance and paint 4 adhesion was observed on electrozinc-iron and steel for low zinc as compared to high zinc/high nickel. In particular, Examples 2 and 4 showed excellent corrosion resistance and adhesion when compared to the other formulations when spray applied.

In surmry, hot-dip galvanized and electrozinc show consistent improvement with low zinc/high nickel phosphate baths over either low nickel/high nickel phosphate baths over either low nickel/low zinc or high nickel/high zinc baths. This is because of increased nickel content in the phosphate coating.

Electrozinc-iron and steel show an inconsistent or slight improvement related to the level of nickel in the phosphate coating, but a large improvement related to ,the level of phosphophyllite in the coating. Galvanneal does not clearly show inprovernent related to Phosphonicolite or phosphophyllite levels in the coating.

-29- 043.069 In the following section, this data will be related to the solubility of the phosphate coating in alkaline media.

ALKALINE SOLUBILITIES OF PHOSPHATE COATINGS S Table XIII below and Figures 11-15 show that low zinc/high nickel compositions as represented by Example 5 are superior to low zinc/low nickel compositions when tested for solubility in alkali solutions. No real improvement in resistance to alkaline attack was shown on steel panels; however, resistance to alkaline attack on pure zinc substrates, such as hot-dip galvanized and electrozinc, is substantially increased with higher nickel content bath. Galvanneal shows no increase in resistance to alkaline attack based upon the nickel content.

Electrozinc-iron shows a slight increase in resistance.

Ii a- TABLE XIII Alkaline Solubilities of Phosphate Coatings Percentage of Coating Insoluble In Alkalkl* Type of Phosphate Low Zinc High Nickel Low Zinc Low Nickel Concentrate Used Example 5 Example 12 Steel 27% 24% Hot Dip Galvanized 28% Electrozinc 38% 17% A01 Galvanneal 36% 37% Electrozinc-Iron 32% 26% Solubilities of the galvanized products are higher than expected because of a redeposition of white powder associated with attack on the substrate. Spray phosphate coatings.

Figures 16-20 show that higher nickel/zinc ratios in the boundary layer can be correlated with decreased corrosion and/or paint adhesion loss.

Electrozinc, hot-dip galvanized and, to a lesser extent, electrozinc-iron all show L decrease in alkaline solubility at higher nickel/zinc ratios, and all shov a decrease in corrosion and/or paint loss. A01 galvanneal does not show a decrease in alkaline solubility or a decrease in corrosion and paint loss due to a higher nickle to zinc ratio in the boundary layer. No significant changes are noted in L 043.069 the alkaline solubility because there is such a small change in the nickel/zinc ration in the boundary layer. It is interesting to note that the data available suggests that if the nickle/zinc ratio for steel were raised, then it would improve the painted corrosion resistance or paint adhesion.

ACCELERATED TESTING FOR NICKEL AND FLUORIDE The coating comnpositions of Example 13 and Example 14, having different levels of aimonium bifluoride, were applied to cold-rolled steel and hotdip galvanized as well as electrozinc substrates. The test results show that high nickel phosphate baths based on low zinc/high nickel are superior to phospDhate baths having low zinc/low nickel for steel, hot-dip galvanized and electrozinc.

Tables XIV and XV below show that fluoride does not substantially affect the quality of the phosphate coating for a high nickel bath over the range of 0-400 ppm.

TABLE XIV Accelerated Testing for Nickel and Fluoride+

CSC

FSC

0 3.4 Fluoride 0 185 385 590 780 975 0 185 385 590 780 975 185 385 590 780 975 Spray Phosphate Substrate

MIS

CRS

CRS

CRS

CHS

CRS

HO

HOG

HOG

HO

HOG

HOG

EZ

EZ

EZ

EZ

EZ

EZ

Law Nickel High Nickel Example 13 Examp~le 14 t71 Coss S~rib Cross, Srfn 5 5mm 5 5mw 5 4mm 5 6mwn 5 Snsw 5 Srn 5 4mw 5 5mm 5 Sara 5 4msm 4+ 2mm 4+ 4mwr 3+ 2mm 5 4rm 4+ 2rmm 5 Sim 3+ 2rsew 5 5mw 3+ 2mm 5 4ram 3+ 2rm 5 2nm 5 2mm 5 2mm 5 2mm 5 5aIT) 5 1(115 5 2amn 5 1mm 5 2mw 4 1am 5 2mw 5 2msin 5 Law Zinc Low Nickel Example 13 Q7lb Coss Hatch 51m 5 4mm 5 Swim 5 '4mwr 5 4Ms 5 4mwr 5 $mm 4+ BRMw 3+ &Tiw 1 a1m 0 am 0 5mw 5 6mw 5 4am 5 4ram 5 5Mw 4+ 5mmi 5 Law Zinc High Nickel Example 14 S~rirbe Cross n) Hatch 3mw 2mm 211* 3anm 4mm 3rm 4+ 71115 7afm 7arm 6mw 6m am 4+ Sam 4mw 3mwr 4mw 4mm 4mw 2 -31- 04 3.0 69 TABILE XV Accelerated Testing for Nickel and Fluoride+

ASC

V. v0 0 a 0 no0~' 25.4 a five Fluoride porn 0 185' 385- 590 780 975 0 185 385 590 780 975 0 185 590 780 975 Spray Phosphate Substrate

CRS

CRS

Ci'S

HDG

IIDG

HDG

HDG

HDG

EZ

EZ

EZ

EZ

EZ

Low Nickel High Nickel Example 13 Example 14 S bc noo S Crb ross rTn hatch (fn Hatch linen 5 orn 5 rm 5 Vomn 5 8nrn 5 7nxn 5 Orun 4+ om 5 6rnen 5 11ifl 5 Sam 5 l10ru 5 Icon 4 2mrn 4+ 3cm 2 lois 4+ 3rnm 2 2rrm 3+ 3Inn 2 loon 5 ln 2 loorn 5 3rn 2+ loon 4+ 2Inin 4+ loon 5 3mm 5 loo~n 5 3rrr 4+ 2inn 5 2mnm 5 loin 5 Icon 4+ loon 5 3com 4 2mnm 5 S7rb Cros ]latch l9rro 4 8mmr 4+ 11cnm 4 lOmri 4+ Soon 4+ loom 2 lon 1+ 5omn 2 Failure Failure Orun 4 im 3 rn 3 Irrm 4 horn 3+ Low Zinc Low tinc Low Nickel High Nickel Examp~le 13 Exampjle 14 7nr l6m 7mm cm imm Ors Ornm 0mm Coss Hatch 4+ 4+ 4+ 4+

I

3 3 3.

3 4 4+ 4+ ZINC MANGANESE NICKEL PHOSPHATE COPOSITIONS Additional testing has been conducted to determine the effectiveness of adding manganese and nickel to zinc phosphate coating solutions having preferred ratios of zinc to nickel. Also, formulations incorporating nitrite, hydrazine and hydroxylamine have the effect of reducing the manganese precipitation and producing a clearer bath solution.

The compositions were tested as previously described and are listed above as Examples 15 and 16.

4130".

440 TEST RESULTS OF MANGANESE ZINC PHOSPHATES.

Examples 10, 12, 15 and 16 were compared to determine the effect of the addition of manganese to both a low zinc/low nickel composition as represented by Example 12 and and a low zinc/high nickel composition as represented by Example 10. The nickel and manganese contents of manganese- -32- 043.069 containing zinc phosphate coatings and comparable panels from non-manganese baths are shown in Table XVI below: TABLE XVI Composition of Manganese Zinc Phosphates* 5. Tpe of Phoshpate Low Zinc Lw Zinc Low Zinc Lw Zinc Low Nickel Low Nickel High Nickel High Nickel High Manganese High Manganese Concentrates Used Example 12 Example 15 Example 10 Example 16 Nickel Content Steel 1.0% 0.6% 1.5% Ilot Dip Galvanized 0.9% 0.7% 1.6% 1.1% Electrozine 0.8% 0.7% 1.2% Electrozinc-Iron 0.9% 0.7% 1.4% Manganese Content Steel 3.0% 2.6% Ilot Dip Galvanized 2.9% 2.6% Electrozinc 2.7% Electrozinc-Iron 3.3% 2.4% Imersion Phosphate When manganese is included in the bath, the nickel content of the coating drops. This is because the manganese in the boundary layer also competes with the nickel for inclusion in the phosphate coating. As will be shown lt 26. below, the addition of manganese to the bath does not cause a drop in performance, but in some instances actually shows improvements. Since manganese S" is generally less expensive than nickel, a manganese/nickel/zinc phosphate bath may be the most cost-effective method of improving resistance to alkaline solubility. Quantitative testing of the alkaline solubility of manganese/nickel/zinc phosphate coatings is not possible since the ammnonium dichromate stripping method was not effective in removing the coating. However, qualitatively the decrease in S.alkaline solubility of manganese/nickel/zinc phosphate is clearly shown by the increased resistance to the alkaline stripping method that was effective -on nickel/zinc phosphate coatings.

-33- 4,

I

i i i i 043.059 CORROSION AND ADHESION TEST RESULTS The manganese/nickel/zinc phosphate coatings were tested by the indoor scab test with the results shown in Table XVII below: Type of Phosphate Concentrates Used TABLE XVII 140° F IDS TEST RESULTS* Low Zinc Low Zinc Low Nickel Low Nickel High Manganese Example 12 Example 15 Scribe Cross Scribe Cross (rni) Hatch (mn) Hatch 3nrn 5 4nn 5 4Tm 5 4nrn 5 4rmn 4+ 3am 5 Irmn 4 Inm 4+ Low Zinc High Nickel Exarrple 10 Srilb Cross r) Hatch 3mn 5 3mn 5 3n 5 2rrn 54+ Ocrn 4+ Low Zinc High Nickel High Manganese Example 16 Scrib Cross m Hatch 3mn 3nln 2mrn Inm 4+ Steel Hot Dip Galvanized Electrozinc Electrozinc-Iron Immersion Phosphating Table XVII shows that the test results for low zinc/low nickel and low zinc/high nickel compositions having manganese added thereto are substantially equivalent as applied to steel, hot-dip galvanized, electrozinc and electrozinc-iron substrates. The exception is that electrozinc shows improvement with additions of manganese to the low nickel bath. The test results were obtained on panels that were coated by immersion phosphating.

NITROGEN-REDUCING AGENTS Substantially equivalent phosphate concentrate having manganese oxide were prepared using a reducing agent to limit precipitation during manufacture. Some effective reducing agents were nitrite, hydrazine, hydroxylamine when added in the proportions shown below in Table XVIII: 7 -34- -22- 043.069 TABLE XVIII Effect of Nitrogen-Reducing Agents on Manganese Phosphate None Nitrite Hydrazlne Hydroxylamine Water 46.4% 46,4% 46.0% 46.2% Phosphoric Acid 40.2% 40.2% 39.9% 40.0% Sodium Nitrite 0.38% lHydrazlne SuiTate 0.75% Ilydroxylamine Sulfate 0.75% Manganese Oxide 9.10% 9.10% 9.03% 9.06% Nitric Acid 3.72% 3.49% 3.76% 3.47% Nickel Oxide 0.45% 0.45% 0.45% 0.45% Solution Clarity muddy brown slightly cloudy clear clear Precipitate heavy brown slightly brown none none Table XVIII and all other concentrates in this section show the ingredients in the order added.

The results of the above comparative test indicate that the hydrazine and hydroxylarnine reducing agents were completely effective in Sobtaining a clear solution and eliminating precipitation from the baths. The sodium nitrite was moderately effective in clarifying the solution and partially effective in t that it reduced the degree of precipitation. Therefore, the addition of sufficient amounts of nitrogen containing reducing agents can eliminate or greatly reduce the precipitation and clarity problems. The quantity of reducing agent required is expected to be dependent upon the purity of the manganese alkali. The quantity of reducing agent is limited primarily by cost considerations. The reducing agent is preferably added prior to the manganese and prior to any oxidizing agent.

Another key factor is the ratio of manganese to phosphoric acid. Table XIX shows the effect of variations of the manganese/phosphoric acid ration on the clarity of the concentrate.

i I~ I! 043.069 TABLE XIX EFFECT OF MANGANESE: PHOSPHORIC ACID RATIO Example Example Example Example Name of Raw Material XVII XVIII XIX XX Water 41.1% 42.3% 43.5% 46.5% Phosphoric Acid 48.0% 46.8% 45.5% 42.3% Hydroxylamine Sulfate 0.52% 0.52% 0.52% 0.53% Manganese Oxide 10.4% 10.4% 10.5% 10.7% Clarity Clear S1. Cloudy Cloudy Voluminous White ppt.

Mn:H 3

PO

4 Molar Ratio 0.378:1 0.388:1 0.403:1 0.441:1 Clearly, the manganese:phosphoric acid molar ratio should be between 0.388:1 and 0.001:1. As in all concentrates, the less water added the better as long as no precipitate is formed. Table XX shows the effect of increasing the concentration of the concentrate. One of the traits of manganese phosphate concentrates is that they form moderately stable super-saturated solutions. Thus, in order to determine whether or not a solution has been formed that will not precipitate during storage, the concentrates must be seeded.

I ir t ibr I Name of Raw Material Water Phosphoric Acid (75%) Hydroxylamine Sulfate Manganese Oxide Manganese Concentration Mn:H 3

PO

4 Molar Ratio Initial Solubility Solubility after Seeding TABLE XX EFFECT OF CONCENTRATION Example Example XXI XXII 31.8% 36.4% 55.6% 51.8% 0.60% 0.56% 12.0% 11.2% 2.42 m/i 2.24 m/1 0.388:1 0.388:1 All Soluble All Soluble Massive All Soluble Precipitation Example

XXIII

41.1% 48.0% 0.52% 10.4% 2.06 m/l 0.388:1 All Soluble All Soluble Thus, the concentration of manganese should be 2.24 m/1 or below.

We claim: -36- _i i

Claims (3)

10. 0* 0 1 0 00* 0 0 0 400 a *0 000,°0 0 0 0 0 o a e 2 a l2

20. THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:- 1. A method of phosphate conversion coating metallic substrates selected from the group consisting of steel, zinc-coated steel, and aluminum comprising the steps of: cleaning the surface of the substrates with an alkali cleaner; conditioning the surface of the substrates with a titanium containing aqueous solution; coating the surface of the substrates with a solution comprising an aqueous solution of the constituents A, B, and C combined in the ratio of 4 to 40 parts by weight A:2 parts by weight B:1 to 10 parts by weight C, and B is provided at a concentration of between 300 ppm and 1,000 ppm, wherein A is selected from the group consisting of potassium, sodium and ammonium ions present as a phosphate salt; B is zinc ions; and, C is selected from the group consisting of nickel, or nickel and manganese; applying said coating composition to the surface of the substrates at a temperature of between 1000 and 1400 F. for between 30 and 300 seconds; and rinsing said substrates. 2. The method of claim 1 wherein said constituents are combined in a ratio of from 8 to 20 parts by weight A:2 parts by weight B:2 to 4 parts by weight C, and the concentration of B is between 500 to 700 ppm. -37- Ai- I_ 0 A Q 0 9 a o 0 60 e* 0 9 9 0 00 o o9 0 0 00 a 90 o 9 a a oeo0000 a 20. 0 0 3. The method of claim 1 wherein said constituents are combined in a ratio of 10 parts by weight A:2 parts by weight B:3 parts by weight C, and the concentration of B is between 500 to 700 ppm. 4. A method of coating substrates selected from the group consisting of steel, zinc-coated steel, and aluminum comprising the steps of: cleaning the substrates with an alkali cleaner; conditioning the surface of the substrates with a titanium containing aqueous solution; preparing a coating composition by diluting in an aqueous bath first and second concentrates; said first concentrate comprising in weight percent: Water 0-80% Phosphoric Acid 10-60% Nitric Acid 2-35% Zinc Oxide 2-15% Nickel Oxide 1.5-25% Sodium Hydroxide 0-10% Ammonium Bifluoride 0-10% Sodium Salt of 2 Ethyl Hexyl Sulfate 0-1% Nitro Benzene Sulfonic Acid 0-0.1% said second concentrate comprising in weight percent: Water 30-80% Phosphoric Acid 10-35% Nitric Acid 0-15% Sodium Hydroxide 0-30% Potassium Hydroxide 0-45% -38- -b~ n 1C Y I- l- L ii I said aqueous bath having a zinc ion concentration of between 300 to 1,000 ppm, an alkali metal ion concentration from an alkali metal phosphate of between 600 and 20,000 ppm, and a nickel ion concentration of between 150 and 5,000 ppm; applying said coating composition to the surface of the substrates at a temperature of between 1000 and 1400 F. for between and 300 seconds; rinsing said substrates; applying a chromate rinse to the substrates; and rinsing said substrates with water. ,.0o 5. A method of coating a substrate selected from the group S consisting of steel, zinc-coated steel, and aluminum comprising the steps of: cleaning the substrates with an alkali cleaner; conditioning the surface of the substrates with a titanium containing aqueous solution; preparing a coating composition by diluting in an aqueous bath first and second concentrates; said first concentrate comprising in weight percent: •Water 10-50% Phosphoric Acid 20-45% Nitric Acid 5-25% 25 Zinc Oxide 4-9% Nickel Oxide 3-18% 0 0 Sodium Hydroxide 0-6% o0o Ammonium Bifluoride 0.2-5% Sodium Salt of 2 Ethyl Hexyl Sulfate 0.2-0.5% Nitro Benzen Sulfonic Acid 0-0.1% said second concentrate comprising in weight percent:

39- :0 0l4 Water 30-60% Phosphoric Acid 20-35% Nitric Acid 0-10% Sodium Hydroxide 0-30% Potassium Hydroxide 0-45% said aqueous bath having a zinc ion concentration of between 500 and 700 ppm, an alkali metal hydroxide ion concentration of between 2000 and 7000 ppm, and a nickel ion concentration of 30. between 500 and 1,050 ppm; 0 A o° .applying said coating composition to the surface of the substrates at a temperature of between 100° and 1400 F. for between 30 and 300 *seconds; 09. rinsing said substrates; applying a sealing rinse to the substrates; and rinsing said substrates with water. 6. A method of coating a substrate selected from the group consisting of steel, zinc-coated steel, and aluminum comprising the steps of: cleaning the substrates with an alkali cleaner; 5. conditioning the surface of the substrates with a titanium t containing aqueous solution; preparing a coating composition by diluting in an aqueous bath first and second concentrates; said first concentrate comprising in weight percent: Water Phosphoric Acid 38% Nitric Acid 21% Zinc Oxide Nickel Oxide 8% Sodium Hydroxide 4% I-I- r,-L i Ammonium Bifluoride 2% Sodium Salt of 2 Ethyl Hexyl Sulfate 0.3% Nitro Benzene Sulfonic Acid 0.05-0.1% said second concentrate comprising in weight percent: Water 34% Phosphoric Acid 28% Nitric Acid Sodium Hydroxide 13% Potassium Hydroxide said aqueous bath having a zinc ion concentration of between 500 and 700 ppm, an alkali metal hydroxide ion concentration of between 2000 and 7000 ppm, and a nickel ion concentration of between 250 and 1,050 ppm; applying said coating composition to the surface of the substrates at a temperature of between 1000 and 1400 F. for between 30 and 300 seconds; rinsing said substrates; applying a chromate rinse to the substrates; and rinsing said substrates with water. 25 7. A method of coating a substrate substantially as hereinbefore described with reference to the examples. Dated this 19th day of October 1989 CHEMFIL CORPORATION By their Patent Attorneys COLLISON CO. -41- 4_