JPH072995B2 - Metal surface treatment agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is a metal for removing oxide scale and corrosion products thickly formed on a metal surface such as stainless steel by welding, heat processing such as atmospheric annealing, or natural corrosion. The present invention relates to a surface treatment agent.

[Prior Art and Problems to be Solved by the Invention] Conventional metal surface treatment agents, so-called acid detergents, contain hydrofluoric acid.

For this reason, conventional metal surface treatment agents are subject to strict legal regulations and regulations from the viewpoint of health and hygiene when they are manufactured, stored, transported, displayed, or sold as poisons. The person in charge of handling poisonous and deleterious substances prescribed in Article 7 of the Act had to be assigned and managed.

Further, when the surface treatment is performed, there are problems in occupational health and safety such as irritating odor caused by hydrofluoric acid and severe pain when contacting the skin.

Further, there is also a problem that a fluorine compound such as hydrofluoric acid is a wastewater regulated substance, and its use is restricted in a place without a fluorine compound removing facility.

The present invention has been made in view of such circumstances, it emits a pungent odor and is toxic, does not contain hydrofluoric acid that requires a removal facility at the time of wastewater treatment, and is very easy to manage and handle. It is an object of the present invention to provide a metal surface treatment agent that does not cause any problems in safety and health.

[Means for Solving the Problems]

The metal surface treatment agent according to the present invention is a metal surface treatment agent that removes corrosion products and oxide scale on the metal surface,
Nitric acid 2 to 9.99% by weight, ferric nitrate 5 to 20% by weight, potassium nitrate 1 to 25% by weight, ferric sulfate 5 to 20% by weight, sulfamic acid 5 to 20% by weight, ammonium chloride It is characterized by containing 1 to 20% by weight.

[Action]

The metal surface treating agent comprising the compounding component of the present invention does not contain hydrofluoric acid and effectively removes corrosion products and oxide scale on the metal surface.

Since it does not contain toxic hydrofluoric acid which gives off a pungent odor, it is very easy to manage and handle, and there is no problem in terms of occupational safety and health.

〔Example〕

 Hereinafter, the present invention will be specifically described based on its examples.

The present inventor does not mix any fluorine compound such as hydrofluoric acid, and decides to limit the compounding amount of nitric acid to less than 10% by weight,
As a result of examining various components and blending ratios, it was found that when the components and blending ratios shown in Table 1 were blended, a metal surface treating agent having good performance was obtained.

The reasons for limiting the blending ratio of the components shown in Table 1 are as follows.

Nitric acid is added for removing oxide scale, passivation of metal surface, and leveling. When the compounding ratio is less than 2%, it has no effect, and when it is 10% or more, it is designated as a poisonous substance.

This is because ferric nitrate is added to replenish the nitrate ions, and if it is less than 5%, its effect is not recognized, and if it exceeds 20%, the effect is not improved.

Potassium nitrate is a scale removal accelerator, and if it is less than 1%, its effect is not recognized, and if it exceeds 25%, it significantly accelerates metal corrosion.

Ferric sulfate is added to dissolve the scale, and if less than 5%, the scale does not dissolve, and if it exceeds 20%, ferric sulfate itself does not dissolve.

Sulfamic acid is added as a solubilizing agent, and if it is less than 5%, its effect is not recognized, and if it exceeds 20%, sulfamic acid itself is not dissolved.

Ammonium chloride is added as a dissolution accelerator, and if it is less than 1%, its effect is not recognized, and if it exceeds 20%, it significantly promotes metal corrosion.

The results of actual blending and performance evaluation tests will be described below.

[Numerical example 1] A test plate made of stainless steel (USU304) (2B finish, 100 mm in length, 50 mm in width, 2.5 mm in thickness) was subjected to blank welding on the center line to cause weld beating, which is shown in Table 2. Room temperature (25-30 ℃) in metal surface treatment agent
It was soaked for about 20 minutes.

After the immersion, washing with water was performed to examine the degree of removal of the oxide scale. The oxide scale was completely removed, and a beautiful silver-white pickled skin was exhibited, showing the same effect as the conventional metal surface treatment agent. .

Since the metal surface treating agent of [Numerical Example 1] does not contain hydrofluoric acid which gives off a pungent odor, the working environment during the treatment was good.

[Numerical value example 2] Stainless steel (SUS304) pin (diameter 12 mm, length 54 m
m) was heat-treated to produce an oxide scale, which was immersed in the same metal surface treatment agent as in [Numerical example 1] at room temperature for 120 minutes. After the immersion treatment, the oxide scale was completely removed. Since it does not contain hydrofluoric acid, the working environment during processing was good.

Next, when the above sample was immersed in a conventional metal surface treating agent (containing 15% nitric acid and 5% hydrofluoric acid) at room temperature for 120 minutes, the oxide scale was completely removed.

FIG. 1 (a) is a photograph of a metal structure of a pin surface-treated with the metal surface-treating agent of the present invention, observed by SEM (scanning electron microscope) at a magnification of 500 times, and FIG. 1 (b). ) Is a photograph of a metal structure of a pin surface-treated with a conventional metal surface-treating agent. In FIG. 1 (b), crystal grain boundaries are observed, which shows that the base material is over-etched. On the other hand, in the numerical example shown in FIG. 1 (a), the base material is more beautiful, and it can be seen that only the oxide scale was effectively removed.

[Numerical value example 3] Union ring made of stainless steel (SUS316) (nominal diameter 3
Inch) was hot forged to generate an oxide scale and shot-blasted to remove the oxide scale to some extent, and immersed in the same metal surface treatment agent as in [Numerical example 1] at room temperature for 45 minutes. . After the treatment, the oxide scale was completely removed, and a silver-white pickled skin was exhibited.

Next, the above-mentioned sample is placed in a conventional metal surface treatment agent at room temperature for 45 minutes.
After soaking for a minute, the oxide scale was completely removed.

2 (a) is an SEM photograph showing the metal structure of the union ring surface-treated with the metal surface-treating agent of the present invention, and FIG. 2 (b) is surface-treating with the conventional metal surface-treating agent. It is a SEM photograph showing the metallic structure of the union ring. The metal surface of FIG. 2 (a) does not feel rough, while the metal surface of FIG. 2 (b) shows a rough state. This is remarkable even when touched with a finger, and the surface treated with the metal surface treating agent of the present invention is smooth, whereas the surface treated with the conventional metal surface treating agent is rough.

[Numerical Example 4] A nut (nominal diameter 41 mm) made of stainless steel (SUS304) was hot forged to generate an oxide scale, and shot blasting was performed to remove the oxide scale to some extent. When immersed in the same metal surface treatment agent as above for about 2 hours at room temperature, the oxide scale was completely removed and a silver-white pickled skin was exhibited.

As described above, the metal surface treatment agent of the embodiment of the present invention effectively removes oxide scale from the metal surface and makes it beautiful.

It is needless to say that the compounding ratio of each component of the metal surface treating agent of the present invention is not limited to the compounding ratio of the examples, and can be freely selected within the limited range of each compounding ratio.

Furthermore, although the embodiment of the present invention describes the case of treating the surface of stainless steel, the present invention is not limited to this and can be applied to other metals such as steel.

〔effect〕

As described above, the metal surface treatment agent of the present invention emits an irritating odor and is toxic, and does not contain hydrofluoric acid which requires removal equipment at the time of wastewater treatment, so it can be used even in a place where there is no fluorine compound removal equipment, and occupational safety and health. From the above viewpoint, the processing work can be performed in a good working environment.

In addition, since the content of nitric acid is less than 10% by weight, it is not designated as poisonous and deleterious substances under the Poisonous and Deleterious Substances Control Law, there is no need to assign a person responsible for handling poisonous and deleterious substances, and management and handling are very simple. is there.

Furthermore, the metal surface treatment agent of the present invention effectively removes corrosion products and oxide scale on the metal surface and does not etch more than necessary, and thus can provide a smooth, silver-white and beautifully finished metal surface. For example, the present invention has excellent effects.

[Brief description of drawings]

FIG. 1 (a) is an SEM photograph showing the metal structure of a pin surface-treated with the metal surface treatment agent of the present invention, and FIG. 1 (b) shows the metal structure of a pin surface-treated with a conventional metal surface treatment agent. SEM photograph, FIG. 2 (a) shows the metallic structure of the union ring surface-treated with the metal surface-treating agent of the present invention.
FIG. 2 (b) is a SEM photograph showing a metallic structure of a union ring surface-treated with a conventional metal surface treating agent.

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Claims (1)

[Claims] 1. A metal surface treating agent for removing corrosion products and oxide scales on a metal surface, wherein nitric acid is 2 to 9.99% by weight, ferric nitrate is 5 to 20% by weight, and potassium nitrate is 1 to 25% by weight. %, Ferric sulfate 5-20% by weight, sulfamic acid 5-20% by weight, and ammonium chloride 1-20% by weight.