JPS6090271A - Coating composition for hydrogen absorption - Google Patents

Abstract

PURPOSE:To provide the titled composition capable of suppressing the absorption of atomic hydrogen generated by corrosion into steel, and effective to prevent the hydrogen embrittlement of steel, by adding manganese dioxide to a resin at a specific ratio based on the solid component of the resin. CONSTITUTION:The objective composition is produced by compounding (A) a polymerized oil (preferably blown oil) or a simple or composite natural or synthetic resin (e.g. epoxy resin) with (B) 1-500PHR, preferably 5-100PHR of manganese dioxide selected from natural manganese dioxide, electrolytic manganese dioxide, chemically synthesized manganese dioxide, or their mixture. The particle diameter of the component B is same as that of the pigment-grade manganese dioxide, and the component B may be added with a solvent such as water, ketone, etc. and a pigment, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating composition for suppressing hydrogen absorption, and more particularly, to hydrogen-induced cracking, that is, hydrogen embrittlement cracking, which occurs when atomic hydrogen generated by corrosion of steel is absorbed into steel. The reason for the presence of hydrogen sulfide or carbon dioxide gas in steel is that some of the hydrogen produced by the reaction between hydrogen sulfide and steel diffuses into the steel in atomic form, causing hydrogen embrittlement. It is said that it is good.

Conventionally, in order to prevent this hydrogen embrittlement, it is common to block corrosive factors such as hydrogen sulfide by painting, lining, or the like. Typical methods include adding metal powder (pigment) that reacts with hydrogen sulfide or adding an ion exchange resin to the paint composition1.
The former prevents hydrogen sulfide from reaching the steel surface due to the reaction between metal powder and hydrogen sulfide. The latter causes hydrogen sulfide to react with the ion exchange resin and prevents hydrogen sulfide from reaching the steel surface.

The reaction does not continue indefinitely, and if all the additives react, the effect will be drastically reduced, the corrosion reaction of the steel will increase, and hydrogen embrittlement cracking will occur. Generally, the above-mentioned isolation method takes about 30 hours to 100 days, which is far short of the corrosion resistance of the preparation (several decades).

The present inventors have completed the present invention as a result of intensive research to prevent hydrogen embrittlement cracking by preventing absorption of atomic hydrogen generated by corrosion into steel materials.

That is, the present invention provides a coating composition for suppressing hydrogen absorption, which contains 1 to 500 parts by weight of manganese dioxide per 100 parts by weight of resin solid content.

The manganese dioxide used in the present invention is natural manganese dioxide,
It may be electrolytic manganese dioxide, chemically synthesized manganese dioxide, or a mixture thereof. Electrolytic manganese dioxide is generally prepared by electrolysis of manganese sulfate or manganese chloride. Chemically synthesized manganese dioxide is prepared, for example, by decomposition of permanganate with hydrochloric acid, oxidation of manganese sulfate, or thermal decomposition of manganese nitrate.

The particle size of manganese dioxide is the same as that used for pigments. When the particle size is increased, coating film performance deteriorates.

The vehicle used in the present invention is generally used for paints or linings, and generally polymerized oils, natural or synthetic resins, alone or in combination, are used.

Examples of polymerized oils include mainly boiled oils. Examples of natural or synthetic resins include epoxy resin, epoxy urethane resin, tar epoxy resin, melamine resin,
Examples include chlorine rubber, phenol resin, polyester resin, polyurethane resin, silicone resin, fluororesin, etc. In the present invention, the manganese dioxide has a resin solid content of 100%.
1 to 500 parts by weight, preferably 5 to 10 parts by weight
It is preferable to blend 0 parts by weight.

If the amount exceeds 500 parts by weight, the desired effect cannot be obtained. Moreover, no effect can be obtained even if the amount is less than 1 part by weight.

The coating composition of the present invention may be made into a dispersion using water or other solvents. Examples of other solvents include ketones, esters, glycols, alcohols, hydrocarbon solvents, etc. that are used in general VC paints. Pigments or other additives conventional to coating compositions according to the invention may also be added. Examples of other additives include plasticizers, surfactants, desiccants, hardening UK thickeners, anti-sagging agents, and the like.

The copper phase to which the coating composition of the present invention is applied includes stress corrosion,
Hydrogen embrittlement, hydrogen-induced cracking, hydrogen blisters, etc. occur.
Alternatively, examples of steel materials that are likely to cause such damage include typical high tensile strength steels, oil country tubular goods, transportation pipes, bolts, ships, etc.

Any conventional coating method may be used, such as flow coating, dipping coating, spray coating, brush coating,
Examples include powder coating.

The base material coated with the coating composition of the present invention has a structure in which the steel material hardly absorbs atomic hydrogen generated by corrosion of the steel material in an environment containing hydrogen sulfide, and the effective G prevents hydrogen embrittlement cracking of the copper phase. To prevent. The reason why the coating composition of the present invention prevents hydrogen embrittlement cracking is that manganese dioxide reduces the potential of the steel surface under the coating film to a negative potential (base potential promotes the penetration of atomic hydrogen into the steel material). This seems to be for protection.

The present invention will be explained in more detail by way of examples. External values in the examples are by weight unless otherwise specified.

Example ■ and Comparative Example I A cold rolled steel plate (thickness 0.8-1 JIS G 3141; originally,
To evaluate hydrogen embrittlement, it is necessary to use high-strength steel. In this example, the degree of hydrogen absorption reaction in the steel is expressed, and the effectiveness of this method can be shown by the quality of this hydrogen absorption reaction. Considering that, cold EE rolled steel material is used. ) to obtain a coating film.

The painting method used was spray painting.

For comparison, Table 1 shows the diacid Ihima for 100 parts of resin solid content. 10 than if done by
0 times more sensitive. Therefore, in this application, the measurement time of ty is cut off at 1000 hours, and if the ty point does not exist, t
aged y by 1000 hours.

In Table 2, ty/lx of Example 9 is as small as 15, but since Example 9 is an original model (a type of lining material), ty exceeds 1000 hours when it contains manganese dioxide, and therefore the apparent The top is smaller. That is, it is thought that containing at least manganese dioxide would have an effect more than 15 times greater.

Example 2 This example measures the corrosion potential on the coating side and shows that the composition of the present invention maintains the potential at a reasonable level.

100 parts of melamine-alkyd resin to 10 parts of manganese dioxide
The cold rolled steel material of Example 1 was coated using a paint containing 10 parts of titanium oxide (Y-1), 10 parts of titanium oxide (X-1), and 10 parts of red iron oxide (X-2)'t. 3% NaCl + H2S (gas J saturated liquid was brought into contact with the coating side of the coated plate,
A silver-silver chloride electrode was placed in the saturated solution via a salt bridge, and the potential difference between the salt bridge electrode and the preparation was measured. The results are shown in Figure 2.

As is clear from Figure 2, if the paint does not contain manganese dioxide or contains a substance that reacts with hydrogen sulfide, the corrosion potential of the coated steel will not be maintained at a negative potential, and over time ( On the other hand, in the case of a paint prepared from the composition of the present invention, it is maintained at a positive potential and a hydrogen absorption effect occurs due to an electrochemical reaction.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the change over time of the hydrogen abstraction reaction current on the back side of the coated steel material, and the curve X is a curve showing the change over time of the hydrogen abstraction current of the coated steel sheet using a paint that does not contain manganese dioxide. Curve Y is a curve showing the change over time in the hydrogen extraction current of a coated steel sheet coated with the coating composition of the present invention. FIG. 2 is a diagram showing the change over time in the corrosion potential on the coating side.
Curve X-IH in the figure shows the change in the corrosion potential of a coating preparation that does not contain substances that react with manganese dioxide and hydrogen sulfide. Curve X-2 shows the change in corrosion potential of coated steel containing a substance that reacts with hydrogen sulfide. Curve Y-1 shows the change in corrosion potential of coated steel containing manganese dioxide. Patent applicant Nippon Paint Co., Ltd.

Claims (1)

[Scope of Claims] 1. A coating composition for suppressing hydrogen absorption of steel, containing 1 to 500 parts by weight of manganese dioxide per 100 parts by weight of resin solid content. 2. The coating composition according to item 1, wherein the resin is a natural or synthetic resin, or a polymerized oil alone or in combination. 3. The coating composition according to item 1, wherein the manganese dioxide is natural manganese dioxide, electrolytic manganese dioxide, chemically synthesized manganese dioxide, or a mixture thereof.