JP3073370B2 - Paint base treatment agent for steel surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an undercoating agent capable of removing rust on a steel surface and heat scale of a welded portion, and applying a one-liquid, one-step iron phosphate coating conversion to the removed steel surface. .

[0002]

2. Description of the Related Art Rust generated in various products made of steel and large structures such as hull blocks, particularly during production and storage, or heat scale of a welded portion enhances adhesion to a substrate and rust prevention during painting. Need to be sufficiently removed. Conventionally, such rust and heat scale are removed by mechanical means such as shot blasting or a rotary steel brush. Therefore, workability in terms of working environment is poor, and improvement in process shortening and cost is desired. Was.

For large structures such as hull blocks, after pickling with a 10% phosphoric acid aqueous solution at 50 to 60 ° C.,
Further, there is also a coating base treatment method in which a chemical conversion treatment is performed with an iron phosphate-based solution. However, in this method, since the pickling solution is an aqueous solution containing only phosphoric acid, the temperature of the pickling solution is set to 50 ° C. in order to completely dissolve and remove rust on the steel surface and heat scale at the welded portion completely quickly.
A complicated two-component, two-step process is required, such as requiring a heat source to raise the temperature above, or performing further chemical conversion treatment after pickling because the iron phosphate film formed on the steel surface during pickling is not sufficient. Needed.

[0004]

SUMMARY OF THE INVENTION In view of the state of the art, the present invention removes rust on the surface of various products made of iron and steel and large scale structures of hull blocks and the like, and removes heat scale from welds, and removes iron and steel after removal. An object of the present invention is to provide a coating base treating agent which can treat a surface with an iron phosphate film forming process in one solution and one step to improve the adhesion to a base.

[0005]

The present invention is characterized in that (1) 1,4-naphthoquinone-2-sulfonate and nitrobenzenesulfonate are mixed with a 10 to 20 wt / v% aqueous solution of phosphoric acid. An undercoat agent for painting steel surfaces. (Hereinafter referred to as the first invention) (2) It is characterized in that 1,4-naphthoquinone-2-sulfonate, nitrobenzenesulfonate and a fluorine-based surfactant are blended in a 10 to 20 wt / v% phosphoric acid aqueous solution. An undercoating agent for steel surfaces. (Hereinafter, referred to as a second invention).

The salts of 1,4-naphthoquinone-2-sulfonic acid and nitrobenzenesulfonic acid used in the first and second inventions of the present invention include ammonium, sodium and potassium salts.

The components of the undercoating agent of the first invention and the concentration thereof will be described in detail. The concentration of phosphoric acid is 10 wt / v%.
If the amount is less than the above, it is good if the amount of oxidized scale such as rust and heat scale is light, but if the strength is high, the removability per unit time is lacking at room temperature. 10-2
0 wt / v%.

If the concentration of the 1,4-naphthoquinone-2-sulfonate added as an oxide scale removal accelerator is less than 0.1 wt / v%, the effect of accelerating the removal of oxide scale is lacking and 0.5 wt / v. %, The effect of removing oxide scale is not significantly improved.
5 wt / v% is preferred.

If the concentration of nitrobenzenesulfonate added as an oxide scale removal accelerator and iron phosphate film formation promoting agent is less than 0.1 wt / v%, the effect of promoting oxide scale removal and the effect of iron phosphate film formation can be reduced. Chipping,
If it exceeds 0.4 wt / v%, the effect of promoting the removal of oxide scale and the effect of promoting the formation of an iron phosphate film are not further improved, so that 0.1 to 0.4 wt / v% is preferable.

The purpose of use of phosphoric acid, 1,4-naphthoquinone-2-sulfonate and nitrobenzenesulfonate, which are components of the coating undercoating agent of the second invention, and the range of their addition concentration are described in the first invention. As in the second
The components of the coating base treating agent of the present invention are added with a fluorine-based surfactant for increasing the wetting and penetrating power of the base treating solution to further promote the oxide scale removing effect, and the concentration thereof is 0.005 wt / v. %, The effect of wet and penetrating power is small and lacks synergistic effect on oxide scale removal, and 0.03
Even if the amount exceeds wt / v%, the synergistic effect on oxide scale removal is not significantly improved.
3 wt / v% is preferred.

[0011] The fluorine-based surfactant in the present invention obtained by collectively to a surfactant having a fully fluorinated perfluorocarbon Chie in, as the major chemical name perfluoroalkyl (C ₈ ~ C ₁₂ ) trimethylammonium salt [C ₉ F ₁₉ CONH (CH ₂ ) ₃ N
(CH _{3) 3} I], N- perfluorooctane sulfonyl glutamic acid disodium, N- [3- (perfluorooctane sulfonamide) propyl] -N, N- dimethyl -N- carboxymethylene ammonium betaine,
Perfluoroalkyl (C ₇ ~C ₁₃₎ carboxylic acids, perfluorooctane sulfonic acid diethanolamide, perfluoroalkyl (C ₄ ~C ₁₂₎ sulfonate (K, N
a), N-propyl-N-(2-hydroxyethyl) perfluorooctane sulfonamide, perfluoroalkyl (C ₆ -C ₁₀₎ sulfonamide propyl trimethyl ammonium salts, perfluoroalkyl (C ₆ -C ₁₀₎
-N-ethylsulfonylglycine salt (K) and the like are sold as a fluorine-based surfactant and can be used.

In the method of applying a coating base treating agent according to the present invention, the spray method is preferably more efficient when the object to be treated is large, and may be directly immersed in the substrate treating agent when the object is small.
In addition, when the rust on the steel surface of the object to be treated is mild, the treatment temperature at the time of the substrate treatment is sufficiently applicable as long as the surface treatment agent does not freeze, but if the degree of rust is strong, the temperature is high. As the removal of rust and the formation of the iron phosphate film are accelerated, the spraying or immersion of the undercoating agent is performed in a range of 25 to
About 30 ° C. is preferable.

[0013]

The coating undercoating agent of the first invention of the present invention is obtained by mixing a predetermined amount of 1,4-naphthoquinone-2-sulfonate and nitrobenzenesulfonate with a phosphoric acid aqueous solution. The operation of removing rust on the steel surface and heat scale of the welded portion, and allowing the iron surface after the removal to be treated with one solution and one step of iron phosphate film formation will be described.

In a phosphoric acid aqueous solution, 1,4-naphthoquinone-2-
By adding the sulfonate and nitrobenzene sulfonate together, the rust on the steel surface and the dissolution and removal of heat scale at the welded portion are remarkably accelerated as compared with the phosphoric acid alone aqueous solution, and the steel surface after the rust removal is coated. A dense iron phosphate film is formed to improve the adhesion of the iron phosphate. The mechanism of dissolution and removal promotion of rust and heat scale is not clear,
Compared with the case where only 1,4-naphthoquinone-2-sulfonate is used in combination with the phosphoric acid aqueous solution and the case where only nitrobenzenesulfonate is used in combination, the combined use of both of them has a greater removal effect. 1,4 with power
-It is considered that the synergistic effect of the combination of naphthoquinone-2-sulfonate and nitrobenzenesulfonate with phosphoric acid.

The mechanism by which the iron phosphate film is formed on the steel surface after the removal of rust and heat scale is that when the cleaned steel surface comes into contact with the substrate treatment solution by spraying or immersion, as shown in the equation, Fe + 2H ₃ PO ₄ → Fe (H ₂ PO ₄ ) ₂ + H ₂ Formula 3Fe (H ₂ PO ₄ ) ₂ → Fe ₃ (PO ₄ ) ₂ + 4H ₃ PO ₄ Formula Iron dissolves and consumes phosphoric acid. For this reason, the pH rises at the interface between the steel surface and the processing solution, and the Fe (H ₂ PO ₄ ) ₂ formed by the formula
Is decomposed by the formula to form insoluble iron phosphate [Fe ₃ (P
O ₄ ) ₂ ] is thought to precipitate and adhere to the steel surface. In this case, the nitrobenzenesulfonate contained in the base treatment liquid oxidizes hydrogen generated from the steel surface by the formula into water, and accelerates the reaction of the formula by quickly erasing from the steel surface, and the synergistic effect causes the film to form. The formation time can also be reduced.

The undercoating agent according to the second aspect of the present invention comprises a phosphoric acid aqueous solution and predetermined amounts of 1,4-naphthoquinone-2-sulfonate, nitrobenzenesulfonate and a fluorine-containing surfactant. The mechanism of accelerating the dissolution and removal of oxide scale and the formation of the iron phosphate film by the undercoating agent are basically the same as described in the first invention. By using a fluorine-based surfactant (a fluorine-based surfactant whose wetting and penetrating power is much higher than that of a hydrocarbon-based surfactant), the wetting and penetrating power of the base treatment liquid against rust and heat scale can be reduced. It is considered that this has the effect of further improving the effect of removing oxidized scale such as rust and heat scale.

[0017]

【Example】

Example 1 A test piece (material: hot-rolled steel plate SPHC, dimensions: 50 mm × 50 mm × 2.3 mm) was subjected to high-temperature treatment at 570 ° C. or higher to form a dense mill scale (average scale amount 4 mg / cm ² ). The test specimen was immersed in a beaker containing 125 ml of the coating base treatment liquid shown in Table 1 (first invention) and Table 2 (second invention), and kept at 25 ° C. to visually determine the mill scale removal time. It was measured. Incidentally, the fluorine-based surfactant of the second invention is a perfluoroalkyl (C ₈ ~C ₁₂₎ trimethylammonium salt.
The term perfluoroalkyl (C ₈ -C ₁₂ ) means that the compound was perfluoroalkylated (C ₉ F ₁₉ ) with a mixture of alkyl groups having 8 to 12 carbon atoms. The rust prevention effect test performed thereafter was performed by the following method. The test piece from which the mill scale had been removed was left standing for 20 days as it was to determine the state of rust generation, and the results as shown in Table 1 (first invention) and Table 2 (second invention) were obtained.

[0018]

[Table 1]

[0019]

[Table 2]

(Example 2) MIG welding of CO ₂ (50 mm at the center of 200 mm length) was performed on one side of a test piece (material: SS41 steel plate, dimensions: 200 mm × 50 mm × 3.2 mm).
mm welding) to remove the slag at the bead portion, and then exposed outdoors for 3 months to generate red rust on the entire surface. The test piece 1 thus rusted was placed in a transparent plastic container (300 × 200 × 400) as shown in FIG.
mm) 2 was placed on a test piece stand 3 provided in the inside 2, and 2500 ml of the coating base treatment liquid 4 was put thereinto, and then the chemical pump (made by Iwaki: MD-80) 5 was started to activate a full cone spray nozzle (nozzle hole: The voltage is adjusted with a slide transformer (Yamabishi: S-130-10) 7 so that the injection amount of the base treatment liquid from the diameter 6 (2.4 mm) 6 becomes 4.8 liter / min. The discharge pressure is 1kg / cm
Injection was carried out in ² , and the removal time of the red rust scale was measured by visual judgment, and the results as shown in Table 3 (first invention) and Table 4 (second invention) were obtained.

The subsequent adhesion test with the paint after the base treatment was carried out by the following method. After the test piece from which the red rust scale has been removed is dried as it is, JIS
Airless spray coating of a tar epoxy paint according to K5400 (General Paint Test Method), and after drying at room temperature for 7 days, a deterioration promoting liquid at 60 ° C shown in Tables 5 and 6 (employed by Japan Shipbuilding Research Association) After immersion for 30 days, the paint was subjected to an adhesion test according to JIS K5400 and the results shown in Tables 5 and 6 were obtained.

[0022]

[Table 3]

[0023]

[Table 4]

[0024]

[Table 5]

[0025]

[Table 6]

[0026]

EFFECTS OF THE INVENTION The use of the coating surface treating agent of the present invention removes mill scale, red rust, and heat scale of welds on the surface of steel such as various products made of steel materials and large structures requiring coating. The rust-preventive iron phosphate film is formed on the steel surface after the removal, so that the adhesion of the paint to the base material, which is indispensable for painting, can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus for measuring the effect of an undercoat agent for coating steel surfaces according to the present invention.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-55-1170 (JP, A) JP-A-56-33481 (JP, A) JP-A-57-198272 (JP, A) 17253 (JP, B1) JP-B 33-1458 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22/00-22/86

Claims (2)

(57) [Claims] 1. An aqueous solution of phosphoric acid in a 10-20 wt / v% aqueous solution,
A coating surface treating agent for steel surfaces, which comprises a mixture of 4-naphthoquinone-2-sulfonate and nitrobenzenesulfonate. 2. An aqueous solution of phosphoric acid in a 10 to 20 wt / v% aqueous solution,
A coating surface treating agent for a steel surface, comprising 4-naphthoquinone-2-sulfonate, nitrobenzenesulfonate and a fluorine-based surfactant.