Why have stainless steel rust? When the stainless steel surface of brown rust (points), people is not great surprise of stainless steel, and steel may be a problem. In fact, this is a lack of understanding of stainless steel.
Kind of one-sided view of the error. Stainless steel under certain conditions will be rusty. Stainless steel has had in acid, alkali and salt corrosion medium capacity — that is corrosion resistance. However, the size of its corrosion resistance is the steelitself, with its chemical composition, plus each state, using the conditions and dry cleaning of the atmosphere, there is absolutely excellent anti-corrosion ability, but will move it to the waterfront, in the presence of a large number of salt sea mist, steel is good. So it is not any kind of stainless steel capability in any environment not rust corrosion.
Stainless steel is formed by the surface layer of very thin and fine for the continued infiltration of strong and continue tooxidation, and access to anti-corrosion ability. If there is some reason, this film was the constant destruction, infiltration of air or liquid or metal will continue to keep in isolation of the iron atom out of the formation of oxygen continuously loose rust. A kind of stainless steel in a number of media have good corrosion resistance, but in some other medium, but may occur due to low chemical stability and corrosion. So, a stainless steel corrosion can not have all media.
Metal corrosion, according to management mechanism can be divided into special corrosion, chemical corrosion and electrochemical corrosion of metal corrosion in engineering practice, most belong to electrochemical corrosion.
The main form of corrosion of stainless steel corrosion (surface corrosion), pitting corrosion, crevice corrosion and stress corrosion.
Corrosion is galvanic corrosion of metal surfaces all media phenomenon of corrosion. According to different requirements resorted to different indicators, generally divided into two main categories:
1. Stainless steel refers to the atmosphere and weak corrosion of steel corrosion medium. Corrosion rate of less than 0.01mm is “totally corrosion”; corrosion rate of less than 0.1mm / year, considered “corrosion” of.
2. Corrosion of steel refers to a variety of strong corrosive medium to corrosion of steel.
Pitting corrosion is the metal surface in the most non-corrosive or highly corrosion of mild and scattered occurrence of localized corrosion, corrosion point of common size is less than 1.00mm, the depth is often greater than the surface aperture, light shallow pits those who have serious even the formation of perforation.
Crevice corrosion is occurring in the metal component crevice corrosion pits dot-like view, this is a localized corrosion.
Intergranular corrosion is a selective corrosion damage, it is with the Department, is the microscopic scale localized corrosion, while the macro is not necessarily local.
Stress corrosion cracking (SCC)
Stress corrosion cracking is to bear the stress of the alloy in the corrosive environment because of strong expansion of the alternate failure pattern of a generic term.
General corrosion is used to describe the alloy surface are spoon way to compare the corrosion occurred in the terminology. In case of general corrosion, the village gradually thinner material because of corrosion, corrosion or failure. Stainless steel in strong acid and alkali corrosion may be present round. Comprehensive failure caused by corrosion of the problem is not how worrying, because, this corrosion can often be a simple soak test or inspection Fushi’s literature information predict it.
Source: Zhejiang Yaang Pipe Industry Co., Limited (www.yaang.com)