JPH0245716B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in the rust-preventing surfaces of steel materials such as hot-rolled pickled steel plates, cooled steel plates, and cast iron. Generally, cold-rolled steel sheets and the like are subjected to surface treatment. In other words, since it takes a considerable period of time for these various types of steel plates to be processed and used for their respective purposes after manufacture, they are not subjected to rust prevention treatment such as the application of rust prevention oil or water-soluble rust prevention agents. ing. However, all of these conventional rust prevention methods have the following drawbacks. When anti-corrosion oil is applied, not only does the oil cause stickiness, but the biggest drawback is that a degreasing process is required when the steel plate is used, and the degreasing liquid must be disposed of as waste. Also, if welding is performed with anti-corrosion oil applied, the electrodes will get dirty and smoke will be generated significantly.
There are drawbacks such as an unfavorable working environment. In addition, inorganic salts such as sodium nitrite and sodium borate have been used as water-soluble rust preventive agents, but there are reasons such as the formation of nitrosamines, which are carcinogenic substances, and toxicity, and surface treatments such as chemical conversion treatment, plating, and painting. Due to the negative impact it has on people, their use is becoming less popular. Therefore, organic rust inhibitors have recently come into use. These organic rust inhibitors contain saturated and unsaturated aliphatic carboxylic acids (i.e. formic acid,
Acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, acrylic acid. crotonic acid, isocrotonic acid, undecylenic acid, oleic acid, etc.), saturated and unsaturated aliphatic dicarboxylic acids (i.e. oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, speric acid, azelaic acid) , sebacic acid, maleic acid, fumaric acid, etc.), aromatic carboxylic acids, (i.e. benzoic acid, nitrobenzoic acid, aminobenzoic acid, toluic acid, aminotoluic acid, nitrotoluic acid, phenylacetic acid, cinnamic acid, salicylic acid, etc.) , aromatic dicarboxylic acids (phthalic acid, aminophthalic acid,
nitrophthalic acid, isophthalic acid, terephthalic acid, etc.), triazoles (benzotriazole, methylbenzotriazole, etc.), imidazoles,
A small amount of surfactant (anionic surfactant, cationic surfactant, nonionic surfactant, Many use amphoteric surfactants in combination. In particular, since carboxylic acids have excellent rust prevention properties, most water-soluble organic corrosion inhibitors contain carboxylic acids as a main ingredient. However, when steel sheets are treated with a corrosion inhibitor based on carboxylic acid, the treated surface may darken when dry or when stored for a long period of time. If anti-corrosion oil is applied and stored in stacks, oil staining may occur. The present inventors have conducted intensive research to solve these drawbacks of organic corrosion inhibitors, and as a result, have found a solution by using specific additives. That is, the present invention relates to a method for improving the surface of a steel material, which is characterized by adding the following compound (a) or both of the following compounds (a) and (b) when using a carboxylic acid-based corrosion inhibitor. (a) General formula (X represents a hydrogen atom, a hydroxyl group, an alkyl group, a carboxyl group, or a nitro group) or an alkali metal salt, ammonium salt, or amine salt thereof (b) Ethylenediaminetetraacetic acid or an alkali metal salt, ammonium salt, or amine thereof At least one salt selected from salts A feature of the present invention is that when steel plates treated with only carboxylic acid corrosion inhibitors are stored dry or stacked for a long period of time, the entire treated surface darkens; By adding the agent, the treated surface can be kept clean. Another feature of the present invention is that when a carboxylic acid-based corrosion inhibitor is used as a temper rolling fluid and a steel plate is treated and then coated with rust preventive oil and stored in piles, oil stains occur. By adding the additive of the invention, the problem of oil stain can be solved. Another feature of the present invention is that by adding the additive of the present invention to a water-soluble organic corrosion inhibitor, the rust prevention performance can be further improved. Another feature of the present invention is that it does not adversely affect subsequent surface treatments such as chemical conversion treatment, plating, and painting. The carboxylic acid corrosion inhibitor used in the present invention may be exemplified by known ones, but preferably the saturated and unsaturated aliphatic carboxylic acids, aliphatic dicarboxylic acids, and aromatic carboxylic acids mentioned in the prior art section Examples include carboxylic acid-based corrosion inhibitors such as acids and aromatic dicarboxylic acids. Examples of the compound of general formula (1) used in the present invention include pyridine-2-carboxylic acid, pyridine-3-carboxylic acid, pyridine-4-carboxylic acid, pyridine-5-methyl-3-carboxylic acid, and pyridine-2-carboxylic acid. 4-nitro-3-carboxylic acid, pyridine-5-hydroxy-3-carboxylic acid, pyridine-
2,3-dicarboxylic acids and the like can be mentioned.
In addition, as alkaline agents for making these compounds and salts, sodium hydroxide, potassium hydroxide,
Examples include ammonia, monoethanolamine, monoisopropanolamine, triethanolamine, aminoethylethanolamine, n-hexylamine, and the like. The same alkaline agent as above can be used also when preparing a salt of ethylenediaminetetraacetic acid. In the present invention, a compound represented by the general formula (1) or a salt thereof, or both the compound of the above (a) and (b) ethylenediaminetetraacetic acid or a salt thereof are added to the organic corrosion inhibitor (a), and ammonia It is preferable to use water, hydrazine, aminos (monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, hexylamine, etc.) to adjust the pH to a range of 7 to 11. The organic corrosion inhibitor of the present invention may be used at a commonly known concentration. In addition, the amount of the compound represented by general formula (1) added is about 0.01 to 5% (weight%,
The same applies hereinafter) is preferred, and the amount of ethylenediaminetetraacetic acid added is also preferably in the range of about 0.01 to 5%.
When using both together, the total is approximately 0.02 to 5
%, with each component preferably present at a concentration of about 0.01% or more. Even if the concentration used exceeds 5%, an effect can be seen, but it is not economical. Regarding the addition method, it may be added to the water-soluble organic rust preventive agent in advance, or it may be added separately at the time of use. The present invention will be described below with reference to Examples.
Note that % indicates weight %. Example 1 Caprylic acid 1%, pyridine-3-carboxylic acid
The treatment liquid was a 0.1% aqueous solution adjusted to pH 8 by adding monoethanolamine as a neutralizing agent, and the steel plate was subjected to normal skin pass rolling, part of it was made into a coil shape on the exit side of the roll, and the other part was After applying anti-rust oil, it was made into a coil. Example 2 1% benzoic acid, 1% pyridine-4-carboxylic acid
A coil was obtained in the same manner as in Example 1 by adding isopropanolamine as a neutralizing agent to the aqueous solution and adjusting the pH to 9 as a treatment liquid. Comparative Example 1 A coil was obtained in the same manner as in Example 1 using a treatment liquid whose pH was adjusted to 8 by adding monoethanolamine as a neutralizing agent to a 1% aqueous solution of caprylic acid. Comparative Example 2 A coil was obtained in the same manner as in Example 2 except that pyridine-4-carboxylic acid was not used. Reference Example 1 A cold-rolled sheet whose surface was cleaned using an aqueous solution of 1% aminobenzoic acid and 0.2% ethylenediaminetetraacetic acid (hereinafter abbreviated as EDTA), adjusted to pH 10 by adding monoethanolamine as a neutralizing agent, was used as the treatment liquid. It was sprayed continuously on steel plates, immediately squeezed with a rubber roll, dried with a hair dryer, and then some were stacked as they were, and some were dried and coated with anti-corrosion oil before being stacked. Example 3 4-nitrophthalic acid 1%, pyridine-3-carboxylic acid 0.3%, EDTA-2Na salt 0.2 in terms of EDTA
The same procedure as in Reference Example 1 was carried out using a treatment solution whose pH was adjusted to 9 by adding triethanolamine as a neutralizing agent to an aqueous solution of 1.5%. Example 4 3-nitrophthalic acid 0.5%, azelaic acid 0.5
The same procedure as in Reference Example 1 was carried out using a treatment solution whose pH was adjusted to 10.5 by adding monoethanolamine to a 0.05% aqueous solution of pyridine-4-carboxylic acid. Reference Example 2 N-alkyl-β-aminopropionic acid was added as a surfactant to an aqueous solution of 0.5% sebacic acid, 0.4% 1,2,3-benzotriazole, and 2% EDTA.
The same procedure as in Reference Example 1 was carried out using a treatment solution in which 0.1% was added and the pH was adjusted to 9 using monoisopropanolamine as a neutralizing agent. Comparative Example 3 The same procedure as Reference Example 1 was carried out except that EDTA was not used. Comparative Example 4 The same procedure as Example 3 was carried out except that pyridine-3-carboxylic acid and EDTA-2Na salt were not used. Comparative Example 5 The same procedure as Example 4 was carried out except that pyridine-4-carboxylic acid was not used. Comparative Example 6 The same procedure as Reference Example 2 was carried out except that EDTA was not used. The coils in Examples, Reference Examples, and Comparative Examples were 1
Table 1 shows the performance evaluation regarding the occurrence of rust and oil stain when left for several months and after performing the following wet box storage test. Wet box storage test is 10×10cm
After tightening 10 test pieces in a small vise,
For those without oil in a wet box at ℃, 85%RH
Tests were conducted for 15 days, and for those coated with oil, for 30 days. Performance evaluation was performed based on the following criteria. ◎; No change ○; Slight black discoloration △; Discoloration and oil stain observed ×: Discoloration and oil stain as well as a small amount of rust observed. XX: A large amount of rust is observed. As is clear from the table, the method of the present invention eliminates the blackening of the treated surface that occurs when a water-soluble organic corrosion inhibitor is used, and also eliminates the blackening that occurs when the treated surface is further treated with a rust preventive oil. This not only solves the oil stain problem, but also further improves rust prevention performance.

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Claims (1)

[Claims] 1. When using a carboxylic acid corrosion inhibitor,
A method for improving the surface of a steel material, characterized by adding the following compound (a) or both the following compounds (a) and (b). (a) General formula (X represents a hydrogen atom, a hydroxyl group, an alkyl group, a carboxyl group, or a nitro group) or an alkali metal salt, ammonium salt, or amine salt thereof (b) Ethylenediaminetetraacetic acid or an alkali metal salt, ammonium salt, or amine thereof At least one type selected from salt.