JPH0211671B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a black coloring agent used to form a black oxide film on the surface of steel materials. Traditionally, the so-called black coloring of steel surfaces has two purposes: to protect the steel surface from corrosion caused by acids, moisture, salt, etc. in the natural environment, or from rust caused by oxidation, and to improve the aesthetic appearance of the surface. Therefore, it is widely applied to gun parts, tools, camera parts, sewing machine parts, optical equipment parts, etc. The black coloring agents used for this black dyeing include sodium hydroxide (NaOH), disodium phosphate (Na ₂ HPO ₄ ), sodium nitrate (NaNO ₃ ), sodium nitrite (NaNO ₂ ), and sodium cyanide. A so-called alkaline black colorant having a composition containing an appropriate amount of (NaCN) or the like is generally used, but the following problems have been pointed out with respect to the conventional black dyeing colorant having such a composition. That is, the black density of the treated surface differs depending on the type of steel material. For example, steel materials with a high carbon content can be colored with a desirable black color, but steel materials with a high content of elements other than carbon may have a lighter color density. When coloring a material assembled from multiple parts of different steel materials under the same conditions in order to achieve a reddish hue, it is necessary to separately set the appropriate coloring treatment time through a preliminary test. We spend a lot of effort on controlling the quality of steel materials,
Despite this, it is difficult to obtain an oxide film with a sufficiently uniform black density. In addition, the oxide film formed by the conventional black coloring agent is porous and the bond between the steel base material and the formed oxide film is weak, and as shown in the cross-sectional view of FIG. A large number of cracks 3 occur in the formed oxide film 2, and the durability of the oxide film 2 itself is insufficient.Also, oxidation of the surface of the internal steel material 1 is promoted through the cracks 3, and due to aging, it becomes relatively At an early stage, the black oxide film changes color or fades, and eventually develops into an unsightly rusty state, resulting in poor corrosion resistance. This means that the oxide film 2 with a seemingly satisfactory black density immediately after treatment with a conventional black dye colorant can be heated to about 150°C.
This is evident from the fact that it easily turns red when exposed to high temperatures for 15 to 16 hours continuously. In view of the problems of conventional black coloring agents for steel materials, the present invention provides excellent corrosion resistance and heat resistance of the oxide film formed by the treatment, and is independent of the material of the steel material. This product was developed with the aim of providing a black coloring agent that can form an oxide film with uniform black density.As a result of extensive research, it was discovered that a small amount of black coloring agent with a conventional composition was combined with specific additives. The present invention was achieved by discovering that the above object can be achieved by adding these substances. That is, the present invention uses an alkali black coloring agent containing sodium hydroxide, sodium nitrate, sodium nitrite, etc. as a base, and 2-mercaptobenzothiazole, 2-mercaptobenzothiazole, etc.
This is a black coloring agent containing a small amount of 1,2,3-benzotriazole and n-octadecyl chloride. Examples of conventionally commonly used black coloring agents include NaOH (45 to 50% by weight) (hereinafter, % means % by weight), Na ₂ HPO ₄ or
There are black dye colorants made up mainly of a blend of NaNO ₃ (5-10%) and NaNO ₂ (approx. Some contain added sodium chloride (NaCN), urea, etc. On the other hand, in the black coloring agent of the present invention, three types of compounds consisting of 2-mercaptobenzothiazole, 1,2,3-benzotriazole, and n-octadecyl chloride are based on the above-mentioned alkali black coloring agent. 0.2 each for the dyeing treatment liquid composition used as the agent.
It is added in combination in the range of ~0.8%, preferably in the range of 0.4 to 0.6%. Addition amount is 0.1% or less and 1.0% respectively
In the above cases, a fully satisfactory black oxide film cannot be obtained. Next, in order to form a black oxide film on the surface of a steel material using the black dye colorant of the present invention, first dissolve the black dye colorant in water to form an aqueous solution with a concentration of about 800 to 950 g/concentration. is heated to 115-150°C to obtain a dyeing treatment solution. The material to be dyed, the surface of which has been cleaned in advance, is immersed in this dyeing solution for 20 to 40 minutes. After the immersion is completed, the material to be dyed is removed from the dyeing solution and the dyeing solution adhering to the surface is removed with washing water, thereby making it possible to obtain a desired black oxide film with no color unevenness. In this case, the temperature of the dyeing solution is 115℃.
At lower temperatures, the black color of the finished oxide film tends to become lighter, and at temperatures above 150°C, the surface of the finished oxide film tends to become rough. In addition, if the dyeing solution made of the black dye colorant of the present invention ages due to repeated use, it can be made active by mixing an appropriate amount of an oxidizing agent such as manganese dioxide or sodium hypochlorite into the dyeing solution. and further promote the formation of a black oxide film. The oxide film formed on the surface of the steel material using the black coloring agent of the present invention is dense and robust, and has a strong bond with the base steel surface, and as shown in the cross-sectional view of FIG. 3 is never formed. Therefore, even if the steel material 1 is made of different materials, it is possible to form a uniform black oxide film without causing discoloration or color unevenness, and it also has excellent corrosion resistance and greatly improves the rust prevention effect. Confirmed by ray microanalyzer, X-ray diffraction, heat reddening test, salt spray test, etc. In addition, in the black coloring agent of the present invention, if only two or less of the three additives consisting of 2-mercaptobenzothiazole, 1,2,3-benzotriazole, and n-octadecyl chloride are added, the above-mentioned It has become clear from the results of numerous preliminary tests that excellent effects cannot be obtained, and the above-mentioned excellent effects were achieved for the first time by adding a small amount of the above three types of additives to conventional black dye colorants. What we find is a surprising fact. Regarding the mechanism by which such an effect is obtained, the sulfur compound 4 consisting of 2-mercaptobenzothiazole and the chlorine compound 5 consisting of n-octadecyl chloride are not simply added to the main ingredients, but the sulfur compound 4 and the chlorine compound 5 has excellent reactivity and has the function of promoting the formation of the oxide film 2 during the dyeing process, and the surface of the steel material 1 and the layer of the oxide film 2 strongly adsorb and bond to each other, resulting in more dense oxidation. A film 2 is formed, which is dense and therefore robust, has excellent corrosion resistance and heat resistance, and has an excellent antirust effect. Example 1 Sodium hydroxide 67.5%, sodium nitrate 15.5%
%, sodium nitrite 15.5% as the main component, 2-mercaptobenzothiazole 0.5%, 1,
The black dye coloring agent of the present invention containing 0.5% of 2,3-benzotriazole and 0.5% of n-octadecyl chloride was dissolved in water at a concentration of 870 g/145
The temperature was raised to ℃. JIS as a test piece
Gun barrel (cut to 100mm) made of steel material specified in SCM-435 and JIS SCM-
425, were soaked for 30 minutes, washed to complete the black dyeing, and then subjected to a heat resistance test and a salt spray test using the following method. In addition, as a control test piece, one treated under the same conditions using a commercially available black dyeing colorant Evonol (trade name), which is known as an alkaline black coloring agent, was used. [Heat Resistance Red Discoloration Test] This test measures the extent to which parts of a gun dyed black with a black dye colorant turn red when exposed to high temperatures. This test is necessary to maintain the quality of the gun over the long term, as the gun barrel heats up to a fairly high temperature. The test method is to store 10 test pieces each in a constant temperature dryer heated to 180℃ for 5 to 49 hours, take out a part of the test piece after a certain period of time, and measure the degree of redness by comparing the color difference between the frames. Total (Nippon Denshoku Co., Ltd. ZΣ80 type)
The L type (the lower the numerical value, the blacker the color, and the higher the numerical value, the whiter the color) was measured. The results were as shown in Table 1.

[Salt spray test]

A salt spray test was conducted on each of the 10 test pieces described above using a salt spray tester (CASSER ISO 2F type) in accordance with JIS Z2371. The test conditions were as follows: After the test piece was ultrasonically degreased using 1,1,1-trichloroethane, the salt concentration was 5±.
Salt water was sprayed under the conditions of 1%, test tank temperature of 35° C., and spraying time of 20 to 200 minutes, and the occurrence of red rust after a certain period of time was compared by visual evaluation. The results were as shown in Table 2.

[Table] In the table, ○ indicates a state where no red rust occurred, △ indicates a state where a slight amount of red rust was observed, and × indicates a state where a considerable amount of red rust occurred. From the results in Table 2, it can be seen that the products treated according to the present invention take longer to develop red rust than the control-treated products, and are superior in salt water durability. Example 2 A control staining solution consisting of 45% sodium hydroxide, 10% disodium hydrogen phosphate, 5% sodium nitrite, and 40% water, and 0.5% 2-mercaptobenzothiazole, 1,2,3- Using the dyeing solution of the present invention containing 0.5% benzotriazole and 0.5% n-octadecyl chloride,
Gun parts frames made of steel materials specified in JIS SCM-425 were immersed in the respective dyeing solutions for 30 minutes, and then washed to complete the black dyeing to obtain treated products of the present invention and controls. . The results of heat resistance tests conducted on these treated products according to the same procedure as in Example 1 are shown in Table 3.
The results of the salt spray test were as shown in Table 4.

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【table】

【table】 [Brief explanation of drawings]

Figure 1 is an enlarged conceptual view of the oxide film formed on the surface of steel by the conventional black coloring agent, and Figure 2 is an enlarged conceptual view of the oxide film formed on the surface of steel by the black colorant of the present invention. FIG. 1...Steel material, 2...Oxide film, 3...Crack, 4...Sulfur compound, 5...Chlorine compound.

Claims (1)

[Claims] 1. An alkali black colorant containing sodium hydroxide, sodium nitrate, sodium nitrite, etc. as a base, and 2-mercaptobenzothiazole, 2-mercaptobenzothiazole,
A black coloring agent for the surface of steel materials, characterized in that it contains a small amount of 1,2,3-benzotriazole and n-octadecyl chloride. 2 The alkaline black colorant is sodium hydroxide 50
80% by weight of sodium nitrate, 10-30% by weight of sodium nitrite, and 10-30% by weight of sodium nitrite. 3 2-mercaptobenzothiazole, 1,2,
The method according to claim 1 or 2, wherein the amount of 3-benzotriazole and n-octadecyl chloride is 0.2 to 0.8% by weight, respectively, based on the amount of the treatment solution containing the black dye colorant. Black dye colorant.