Surface-treated stainless-steel sheet with excellent corrosion resistance in salt damage environment for automotive fuel tank

Abstract

A surface-treated stainless-steel sheet with excellent corrosion resistance in a salt damage environment for automotive fuel tanks, characterized by comprising: a ferritic stainless-steel sheet base containing 10.0-25.0 mass% chromium and having an average r value of 1.4 or higher and an overall elongation of 30% or higher or an austenitic stainless-steel sheet base containing 10.0-25.0 mass% chromium and having an overall elongation of 45% or higher and a degree of work hardening of 400 N / mm<2> or lower; and a deposit layer formed over a surface of the base in an amount of 5-80 g / m<2>, the deposit layer containing 5-13 mass% silicon, with the remainder being unavoidable impurities and aluminum. It is further characterized in that the alloy layer formed between the deposit layer and the base iron has a thickness smaller than 5.0 [mu]m, and that it has, formed on the deposit layer, a lubricant coating film which comprises a soluble resin and a lubricity-imparting agent, the amount of the agent being 1-30 mass% based on the soluble resin, and has a coefficient of friction of 0.15 or lower.

Description

technical field [0001] The present invention relates to a surface-treated stainless steel sheet for automobile fuel tanks and a fuel tank excellent in corrosion resistance in a salt damage environment. Background technique [0002] In recent years, fuel system components such as fuel tanks and fuel lines are required to have properties such as fuel permeability prevention and long life due to the need for environmental protection and life-cycle cost reduction. [0003] In fuel tanks or fuel pipes for automobiles, according to the laws of the United States, it is obliged to guarantee the long-term life of 15 years or 150,000 miles of driving. For the three substrates of ordinary steel, resin, and stainless steel, people are developing Fuel train components that meet these requirements. [0004] Among the three substrates of plated steel, resin, and stainless steel, resin has a problem of recyclability; for plated steel, there is some concern about the durability of biofuels ...

AI Technical Summary

Problems solved by technology

[0005] However, at present, the disadvantage of stainless steel is that the corrosion resistance under the salt damage environment is not necessarily enough.

That is to say, in the laboratory accelerated test simulating the exposure to snow melting salt, the problems are: for ferritic stainless steel such as SUS436L, crevice corrosion occurs in the crevice structure or welded structure; Stress corrosion cracking occurs in welded parts, etc.

[0008] However, cationic electrophoretic coating is a method of electrophoresis by immersing the object to be coated in a coating solution, and it is a technology suitable for oil supply pipes in practice; Containers that generate large buoyancy, such as fuel tanks, have the problem of difficulty in application

In addition, there is also a problem that a sufficient anti-corrosion effect cannot necessarily be obtained for a gap having a small gap opening and a large depth.

[0009] In addition, regarding the zinc-rich paint, although the corrosion inside the gap can be suppressed by the cathodic anti-corrosion effect, since this Zn-containing paint contains a large amount of Zn and the resin component is relatively small, it may be inferior to the general paint. poor

Especially in the harsh salt corrosion test, there are often problems such as blistering on the coating film, or peeling of the coating film in extreme cases

If the adhesion of the coating film is to be improved, reducing the Zn content is one method, but if this is done, there is a problem that the intended cathodic anti-corrosion effect will be seriously impaired.

[0010] On the other hand, in the case of aluminum-plated stainless steel sheets as the base material, there is a problem that the plating layer peels off at the stage of forming and processing into fuel tanks and fuel pipes.

The coating for the purpose of long-term anti-rust is usually based on Al or Zn, which can show a sacrificial anti-corrosion effect. According to the necessity of increasing the adhesion of the coating, generally speaking, hot-dip coating is applied, but due to the The formed alloy layer is relatively brittle, so there is a problem that if severe plastic working such as press working is applied to the can, cracks will occur in the alloy layer, and this will be used as a starting point to peel off the plating layer, thereby failing to obtain sufficient anti-rust effect

In addition, there is also the problem that the fragility of the alloy layer will cause cracks during press working

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