JP2506981B2 - Hydrogen embrittlement prevention paint - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydrogen embrittlement prevention coating. More specifically, the present invention relates to a hydrogen embrittlement prevention coating which is applied to a steel material such as a natural gas transportation steel pipe or a gas storage steel material that comes into contact with a fluid containing hydrogen sulfide to block permeation / diffusion of hydrogen sulfide from the coating surface to the steel surface.

Conventional technology Steel materials for this purpose generally react with hydrogen sulfide under weak acidity and show blister generation and hydrogen embrittlement. To prevent this, metal powder that interacts with hydrogen sulfide has been conventionally used. Thermosetting paints containing metal oxides have been applied.

That is, as the metal oxide, in addition to lead oxide, lead monoxide, zinc oxide, cuprous oxide, cupric oxide, etc., alkaline earth metals such as calcium oxide, barium oxide, magnesium oxide, strontium oxide, etc. Has been used. As the metal, zinc, copper, etc. have been used. Also,
As the thermosetting resin, amine-cured epoxy resin, melamine resin-cured epoxy resin and the like have been used.

However, in order to completely block the permeation / diffusion of hydrogen sulfide, there is no pinhole in the coating film, the crack resistance is high, and the impact resistance is high. Although a film was required, in order to ensure sufficient characteristics, in the case of zinc white, for example, fine needle-like or granular zinc white having a size of about 0.1 to 1 μm must be packed at a high density. did not become. Therefore, the coating becomes brittle, and it is difficult to obtain a coating with high impact resistance and crack resistance, and even if sufficient properties can be secured in the initial state, as a result, cracks will occur after long-term use and hydrogen embrittlement It was common to lose the role of anti-paint.

Means for Solving the Problems The present invention has been made as a result of earnest research on the above problems, and by the following means, a highly reactive filler is uniformly distributed in a thin film coating film at a low density to obtain an impact resistance The present invention provides a coating having excellent properties, crack resistance, and hydrogen brittleness prevention effect.

That is, the present invention is that the zinc oxide whiskers are blended in the composition, and the zinc oxide whiskers are composed of a core portion and needle-like crystal portions extending in different axial directions from the core portion, and the needle-like crystal portion. Has a diameter of 0.7 to 14 μm, and a length from the base to the tip of the needle-shaped crystal part is 3 to 20.
The feature is that it is 0 μm.

The zinc oxide whiskers used in the present invention can be produced by heat-treating metallic zinc powder having an oxide film on its surface in an atmosphere containing oxygen. The obtained zinc oxide whiskers have an apparent bulk specific gravity of 0.02 to 0.1, and are highly mass-producible with a high yield of 70 wt% or more. FIG. 1 shows the electron micrograph. According to this, the above-mentioned morphological and dimensional features are clearly recognized. (Hereinafter, it will be referred to as a tetrapot structure.) By the way, the needle-shaped crystal part of the zinc oxide whiskers may be mixed with triaxial, biaxial, or even uniaxial ones. It is thought that the part was broken. In addition, plate crystals may be mixed in. The X-ray diffractograms of these whiskers all show the peaks of zinc oxide, while the electron diffraction distribution results also show the transition,
It showed single crystallinity with few lattice defects. In addition, the content of impurities is low, and as a result of atomic absorption spectrometry, zinc oxide is 99.98.
%Met.

In view of the characteristics of hydrogen embrittlement prevention paint, it is too large (length
In a system with a large proportion of whiskers (larger than 200 μm and diameter larger than 14 μm), the probability that the tetrapot structure will be destroyed in the treatment process will decrease the impact resistance of the coating film, and it should react with hydrogen sulfide. The area is reduced, which is not preferable. On the other hand, in a system in which whiskers are too small (length is smaller than 3 μm and diameter is smaller than 0.7 μm) and a large proportion of whiskers are contained, when the low density (low content) is blended, the specific gravity of zinc oxide is originally large (5.7). Sedimentation and separation make it difficult to uniformly disperse, the hydrogen embrittlement prevention property deteriorates, and the impact resistance and crack resistance decrease, which is not preferable.

For the matrix, all conventionally used resins can be applied, and in particular, thermosetting resins including epoxy resins such as amine-cured epoxy resin and melamine resin-cured epoxy resin can be used.

The blending ratio of zinc oxide whiskers to the matrix is not particularly limited, but if the blending amount is too small, the purpose of preventing hydrogen embrittlement cannot be achieved, and if it is unnecessarily large, the viscosity of the coating will increase and it will be used. It's not good because I can't stand it. Therefore, there is a preferable blending ratio depending on the purpose of applying the hydrogen embrittlement preventing property. That is, it generally depends on the size of the whiskers, the type of resin, and the purpose of use, but is generally 0.
5 vol% to 20 vol% is used, and particularly 3 to 15 vol% gives extremely excellent characteristics.

Furthermore, it is also possible to use zinc oxide whiskers in combination with other fillers such as glass fibers, glass flakes, glass chops, talc, mica, alumina, silica, SiC whiskers, potassium titanate whiskers and the like.

Work Since the zinc oxide whiskers of the present invention have a tetrapot structure, stacking the whiskers makes it possible to realize a sparse space in which the skeleton is stable and the bulk density is extremely small.
By utilizing this structure, it is possible to easily obtain a thick coating film having a low composition (low density) and uniformly dispersed.

Further, since this coating film has a low content, it has a large amount of resin, and in addition, the tetrapod-shaped zinc oxide whiskers themselves have high impact resistance due to the impact absorbing action.

Furthermore, the coating film has improved crack resistance due to the reinforcing effect of the coating film by whiskers.

Next, this tetrapot zinc oxide whisker is a pure single crystal in which each leg extends in the crystallographic C-axis direction,
There is a zinc surface on a plane parallel to the C-axis, and this surface is extremely active for hydrogen sulfide. Since the tetrapot-like zinc oxide whiskers have an extremely large proportion of this active zinc surface, the effect of preventing hydrogen embrittlement becomes particularly large.

Examples The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 Large tetrapod-shaped zinc oxide whiskers (length from the base to the tip of the needle-shaped crystal part: 100 to 200 μm; diameter of the base part:
5 to 14 μm) was prepared, and 5 vol% was mixed with a melamine resin-cured epoxy resin and sufficiently mixed, and then applied on a steel plate (thickness: 500 μm), cured, and an evaluation test was performed.

The evaluation items were the initial impact resistance test and the observation of cracks occurring in the coating film after the heat cycle (-20 ° C / 4Hr + 50 ° C / 4Hr) and the blister (blister) generation state by the hydrogen embrittlement test. The results are shown in Table 1.

After that, when the state of the whiskers in the coating film was observed by SEM, one tetrapot-shaped whisker was broken and changed into a uniaxial, biaxial, or triaxial needle-shaped crystal. Was also observed.

Examples 2 to 3 Exactly the same test as in Example 1 was carried out using medium-sized and small-sized tetrapot-shaped whiskers, and the results are shown in Table 1.

Comparative Examples 1-2 Using the extremely large whiskers and the extremely small whiskers, the same tests as in Example 1 were carried out, and the results are shown in Table 1.

Most of the tetrapot-shaped whiskers in the coating film of Comparative Example 1 were broken and changed into uniaxial needle-shaped whiskers.

Comparative Examples 3 to 6 The same test as in Example 1 was carried out using commercially available zinc white having a granular or acicular shape, and the results are shown in Table 1.

EFFECTS OF THE INVENTION In recent years, the demand for steel pipes for natural gas transportation and gas storage, which require hydrogen embrittlement prevention paints, is increasing. Since the present invention is a high-performance paint invented in response to the demand, its industriality is extremely great.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing the structure of zinc oxide whisker crystals.

Front page continued (72) Inventor Takeshi Hamabe 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Moto Ki Kitano, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial

Claims (2)

(57) [Claims] 1. A zinc oxide whisker is compounded in a composition, and the zinc oxide whisker comprises a core portion and needle-shaped crystal portions extending in different axial directions from the core portion. A hydrogen embrittlement prevention coating characterized in that the base has a diameter of 0.7 to 14 µm, and the needle-like crystal portion has a length from the base to the tip of 3 to 200 µm. 2. The hydrogen embrittlement preventive coating composition according to claim 1, wherein the number of axes in the plural axis directions is 4.