JPH0243798B2 - - Google Patents

Description

TECHNICAL FIELD This invention relates to fluid compositions suitable for application to metal surfaces. The composition may be advantageously used as a lubricant or coolant during metal processing or for corrosion protection of steel coil or sheet packaging articles. The invention further relates to methods of using this fluid composition. During certain metalworking operations, it is common to supply fluid to the metal surface to be machined to reduce friction and also cool the workpiece. In many cases, for example during temper rolling or high speed cutting of steel, aqueous fluids are preferred due to their purifying action. Although the invention will be described herein with particular reference to the example of temper rolling fluids, it should be understood that it may also be applied to other aqueous metalworking fluids, such as cutting fluids. BACKGROUND ART Until now, temper rolling fluids have generally been composed of nitrites to inhibit corrosion and one or more organic amine compounds such as triethanolamine, which acts as a secondary corrosion inhibitor and as a complexing agent. It contained. Such fluids exhibit a number of drawbacks, including the following: 1. Tendency to foam and resulting problems during metal processing. 2. Hygroscopicity and resulting complaints about steel coil or sheet packaging, known as wet packs, which spoil the appearance of the steel surface and are detrimental to paintability. 3. Complaints related to welding machine tip life by steel users. 4. Serious problems in waste disposal and water treatment in rolling mills caused by the presence of amine compounds in such fluids. 5 Due to problems in handling contamination arising from previously used fluids, recirculating the rolling fluid was implemented, but this ultimately presented problems with corrosion control, product cleanliness and fluid deterioration. thing. It is an object of the present invention to provide a processing fluid that avoids or at least alleviates some or all of these problems in use. The present invention provides a rolling fluid that avoids most of the above-mentioned drawbacks while having superior performance substantially comparable to or superior to known rolling fluids in many other respects. In particular, the compositions according to the invention are amine-free and conventionally acceptable for disposal into the environment either with or without disposal after use. This composition has a mild cleaning action and results in a more effective cleaning of the steel strip during skin-pass rolling and a reduced tendency to form wet packages, as compared to the fluids previously used, resulting in a reduction in the tendency of wet wraps to form on the steel surface. Provides improved paintability. The composition according to the invention is suitable for use with steel intended for food grade applications. Rolling fluids according to preferred embodiments are less prone to excessive foaming during use than previously used fluids and are prepared with lower material costs per unit area and reduce the amount of waste contaminants. It can be applied at lower surface coverage than usual for fluids used heretofore and inhibits corrosion of the steel when it is exposed to high humidity after unwrapping. DISCLOSURE OF THE INVENTION The present invention, in a first aspect, comprises sodium nitrite, sodium benzoate, and sodium carbonate, wherein the weight ratio of sodium carbonate to sodium benzoate is in the range of 2:1 to 4:1; The weight ratio of sodium nitrate to sodium benzoate is 9:1 or more
An aqueous composition for coating metal surfaces is provided, characterized in that the ratio is in the range of 15:1. In a second aspect, the present invention provides an aqueous composition for coating metal surfaces, which additionally contains a glycol or a polyol in addition to the above components, and optionally a surfactant. Furthermore, the present invention also provides a method of treating steel, which comprises applying the aqueous metal surface coating composition to the surface of a steel material as a method of using the composition according to the first aspect. BEST MODES FOR CARRYING OUT THE INVENTION Preferred embodiments of the invention will now be described with reference to the following examples. A preferred embodiment of the invention uses an aqueous solution having the composition shown in Table 1 as the concentrate.

Table When intended for use as a temper rolling fluid, this concentrate is typically diluted with water to a 5% v/v processing solution. However, a 2% v/v processing solution is also effective. Formulations having concentrations within the range shown in Table 2 were found to be effective.

[Table] Fatty alcohol ethoxylates 0.09-0.11 Of the components shown in Tables 1 and 2, only nitrite, carbonate and benzoate are essential components. Sodium nitrite acts as the primary corrosion inhibitor. Sodium carbonate acts as an additional corrosion inhibitor and also acts as a moisture wicking inhibitor. Sodium benzoate acts as a secondary corrosion inhibitor. Sodium carbonate and sodium benzoate are also
It acts as a buffer system to maintain the pH in the range from pH 8.5 to 11.5, preferably from pH 10.5 to 11.5.
These effects combine to provide comprehensively excellent corrosion and moisture absorption suppression effects. For this purpose, the weight ratio of sodium carbonate to sodium benzoate is in the range of 2:1 to 4:1 and the weight ratio of sodium nitrite to sodium benzoate is in the range of 9:1 to 4:1.
It is necessary that the ratio be in the range of 15:1. Preferably, the weight ratio of sodium nitrite to sodium benzoate is up to 12:1. It is preferable to suppress the amount of sodium nitrite to 132 g/or less. One or more glycols or polyols, such as glycerol or ethylene glycol, assist in suppressing moisture absorption. It is desirable that a surfactant and preferably a fatty alcohol ethoxylate in the range of 5 to 20 ppm be added to stabilize the surface tension properties of the solution without causing excessive foaming thereof during use of the solution. Alternatively, higher concentrations of low foaming surfactants up to 100 ppm may be used. Preferably,
The processing solution (at 5% v/v for concentrate) was
It has a surface tension of 40-50 dynes/cm. If the rolling fluid is to be applied to steel to be used in food grade applications, preferably food grade or equivalent components should be used.
The formulation does not contain added organic nitrogen compounds such as amines. No special care is taken to eliminate traces of organic nitrogen compounds that may be present as impurities in other ingredients, and such traces are negligible in the industrial grades of ingredients used. It will be understood that it will happen. In use, the processing solution according to the invention is applied, for example by spraying, to a steel strip in temper rolling, preferably at a temperature in the range from 20 DEG to 40 DEG C. As another example, we describe the results of a comparative test using a commercially available amine-containing rolling fluid concentrate (A1) as a control agent. A 5% processing solution (A2) was made therefrom by dilution with water according to conventional practice. A solution with the composition according to Table 1 was prepared (concentrate B1). A 5% processing solution (B2) was made therefrom by dilution with water. Two 20 ton steel coils were rolled in succession in one day, the first one (coil 1) using solution B2 as the temper rolling fluid and the second one (coil 2) using control solution A2. did. Both coils were taken from the same annealing charge. Each coil was cut into two pieces at the rolling mill.
A portion of each was retained for a five month storage trial. Whenever possible for each test, the coils were sampled at the center coil location and tested for edge-to-edge surface coverage. Sampling of the coils in the shear line immediately after rolling showed that even at this stage the solution B2 according to the invention produced a visibly cleaner surface than the control solution A2. Surface coverage analysis (Table 3) showed that solution B2 gave approximately twice as clean a product as when solution A2 was used, based on the turbidity test results. According to the invention
In samples treated with B2, the surface coverage of sodium and nitrite was beneficially lower than that in solution A2.
The amount of adhesion obtained was about 30 to 50% of that obtained when using . A second inspection and sampling was conducted at the shear line two months later. There were no signs of corrosion except at the unprotected coil edges and the condition of both coils was found to be satisfactory. However, coils treated with solution B2 according to the invention have a uniform dry appearance, whereas coils treated with control solution A2 have a "wet package" appearance.
It was observed that it had a greasy appearance that could almost be considered as. Both coils were repackaged for additional storage. After a total of 5 months of storage, the coils were re-inspected and sampled on a shear before being oiled for sale. Both coils are corrosion free and solution free.
The coils treated with B2 were still dry. The coil treated with solution A2 (control) appeared to have undergone absorption and desorption of water and its surface appearance was much more unsightly than that of the coil treated according to the invention. One peculiarity that became apparent during the course of testing was that the turbidity measurements for coils treated with solution A2 decreased, whereas those from coils treated with solution B2 significantly decreased. It was stable. This is considered to be due to the absorption and desorption of water exhibiting an aggregation effect with particulate matter in the coil treated with solution A2. The enlarging grains that form are more easily visible and the strip has a dirty appearance. However, paradoxically,
Cleanliness (as measured by turbidity) is
Larger particles scatter less light, so they increase
A lower turbidity is therefore recorded. Rolling tests were conducted on 10 coils that were temper rolled using a 5% processing solution (B3). The results of sampling during this test are shown in Table 5. Results from two experimental coils and ten full-scale tests show that very consistent low surface adhesion is achieved using the solution according to the invention. Solution A2
Comparison with the results obtained during the investigation of surface coverage when the solution of the present invention was used showed that lower and more consistent coverage was obtained with the use of the solution of the invention.

Table 1 These results show that much better surface coverage uniformity and lower surface coverage are obtained when the solutions of the invention are used. Attempts were made to dilute solution A1 to the 2% level to achieve lower surface coverage, but it was found that using prior art concentrates gave unsatisfactory results. Some of the materials of the invention (eg, ethylene glycol and benzoate) are barely detectable on the product surface even using sensitive liquid chromatography techniques that are more sensitive than 1 ppm benzoate levels. It has also been found that the use of the composition according to the invention improves the corrosion resistance of treated steel under high humidity. Samples of test coils after 5 months of storage were placed overnight in a humidification cabinet at 93% relative humidity. Solution A2
It was found that metals treated with solution B2 rusted, whereas metals passivated with solution B2 were found to be clean; in fact, panels treated with solution B2 showed no visible rust under the most severe conditions. Everything was fine for 5 days until it became clear. The tests were repeated to confirm these results. It is believed that the significant difference in corrosion performance can be explained as follows. After the nitrite on the surface has been consumed by contact with air, the sheet compacted using the control solution A2 has approximately 2 to 5
It has a surface coverage of acetate of mg/ ^m2 . It has been shown that acetate is aggressive towards steel and has high water absorption properties. After the nitrite has been consumed on the sheet rolled with solution B2, only a small surface coverage of carbonate and benzoate (0.2-1 mg/m ² ) remains. These components have low water absorption properties and in addition the benzoate appears to act as a general inhibitor. Benzoates are also apparently more effective as inhibitors against free oxygen access. This corrosion inhibition is particularly beneficial to end users of non-oil immersed coils, such as drum stock manufacturers.
During storage in coil form, passivation is equivalent whether the prior art solution or the solution according to the invention is used. In the unraveled sheet form during subsequent processing, superior corrosion resistance is exhibited by the sheets treated according to the invention, especially under high humidity conditions. In addition, lower surface coverage and generally improved cleanliness result in improved paintability and paint adhesion. It has been found that sheets rolled using recycled prior art solution have a much dirtier appearance than in fresh solution. This is because particulate carbon in the recirculating solution is redeposited onto the strip during temper rolling. To date, approximately 60% of all products have had to be rolled using recycled solutions to minimize waste due to problems associated with contamination. The solutions of the present invention do not need to be recycled and provide a significant improvement in overall product cleanliness over non-oil soaked and oil soaked powder coated products. In addition, it was observed that the emulsification tendency of the oil is much worse when using recirculated solutions, regardless of its composition. This is believed to be due to the presence of contaminants in conjunction with the triethanolamine component in the prior art solutions and such emulsification tendencies are avoided by the use of non-recirculating solutions according to the present invention. Industrial Applicability The present invention provides the following advantages to the metal rolling industry: 1. Provides similar protection in the coiled state to that provided by the prior art compared to conventional nitrites of 5-10 mg/ml.
Apply in a small amount of 1 to 3 mg/m ² instead of m ² . 2. To provide much better corrosion resistance after the sheet is unwrapped than provided by the prior art, especially for non-oil soaked materials. 3. Elimination of organic nitrogen components almost eliminates problems associated with waste water treatment in temper rolling mills and allows the use of non-circulating solutions. 4. A significant improvement in the overall cleanliness of the uncoated sheet is obtained since no solution recirculation is required. 5. The use of lower surface coverage eliminates or virtually reduces the occurrence of wet packs and extends welder tip life. Substantially similar advantages are obtained when fluids according to the invention are used as coolants or lubricants in other metalworking fields.

[Table] is known.

[Table] It is known that

Claims (1)

[Claims] 1. Contains sodium nitrite, sodium benzoate, and sodium carbonate, wherein the weight ratio of sodium carbonate to sodium benzoate is in the range of 2:1 to 4:1, and sodium nitrite to sodium benzoate. The weight ratio is 9:1~
An aqueous composition for coating metal surfaces, characterized in that the ratio is in the range of 15:1. 2. A composition according to claim 1, wherein the concentration ratio of sodium carbonate to sodium benzoate is selected to buffer the solution at a pH value between pH 8.0 and 11.5. 3. The composition of claim 1, wherein the weight ratio of sodium nitrite to sodium benzoate ranges up to 12:1. 4. The composition according to claim 1, comprising 132 g/or less of sodium nitrite. 5 Sodium nitrite, sodium benzoate, sodium carbonate, and glycols or polyols, with a weight ratio of sodium carbonate to sodium benzoate ranging from 2:1 to 4:1 and a weight ratio of sodium nitrite to sodium benzoate. is 9:1~
An aqueous composition for coating metal surfaces, characterized in that the ratio is in the range of 15:1. 6. The composition according to claim 5, further comprising a surfactant. 7. The composition according to claim 5, wherein the glycol is ethylene glycol. 8. The composition according to claim 6, wherein the surfactant is a fatty acid ethoxylate. 9. A composition according to claim 5 or claim 6, wherein the concentration ratio of sodium carbonate to sodium benzoate is selected to buffer the solution at a pH value between pH 8.0 and 11.5. 10. A composition according to claim 5 or claim 6, wherein the weight ratio of inorganic sodium nitrite to sodium benzoate ranges up to 12:1. 11. The composition according to claim 5 or 6, which contains not more than 132 g of sodium nitrite. 12. Claim No. 6 containing, as solutes per liter of solution, not more than 132 g of sodium nitrite, not more than 11 g of sodium benzoate, not more than 44 g of sodium carbonate, not more than 50 g of ethylene glycol, and not more than 0.11 g of surfactant. Compositions as described in Section. 13 diluted to 5% by volume with water and 10.5~
13. A composition according to claim 12 having a pH value of 11.5 and a surface tension of 40 to 50 dynes/cm. 14 comprising sodium nitrite, sodium benzoate, and sodium carbonate, wherein the weight ratio of sodium carbonate to sodium benzoate is in the range of 2:1 to 4:1 and the weight ratio of sodium nitrite to sodium benzoate is 9: 1~
A method of treating steel comprising applying an aqueous metal surface coating composition in the range of 15:1 to the surface of the steel material. 15 Composition is 1.0 to 6.6 per ^m2 of steel surface
15. The method of claim 14, wherein the method is applied to provide a surface coverage of mg of sodium nitrite. 16. The method of claim 14, wherein the composition is applied by spraying onto the surface. 17. The method of claim 14, wherein the composition is applied as a lubricant or coolant before or during metal working. 18. The method of claim 17, wherein the composition is applied as a skin pass rolling fluid before or during skin pass rolling.