The types and definition of stainless steel
In numerous industrial applications, stainless steel can provide satisfactory corrosion resistant performance. According to the use experience, in addition to the mechanical failure, the corrosion of stainless steel is mainly manifested in local corrosion which is a form of serious corrosion such as stress corrosion cracking, pitting corrosion, intergranular corrosion, crevice corrosion and corrosion fatigue. The failure cases caused by local corrosion almost accounts for more than half the cases of failure. In fact, a lot of failure can be avoided by reasonable material selection, such as Martensite stainless steel and Ferritic stainless steel produced by HongChao Stainless Steel, INC.
Stress corrosion cracking (SCC) is a general term which refers to that the alloy withstanding the stress in the corrosive environment is out of work due to the extension of fierce stripes. Stress corrosion cracking has brittle fracture morphology, but it can also occur in the toughness materials. The necessary conditions of stress corrosion cracking are tensile stress (residual stress or applied stress, or both) and a specific corrosive medium. The direction of cracking formation and extension is roughly vertical with tensile stress direction.
Pitting corrosion is a form of leading to local corrosion.
Grain boundary is an intergranular boundary formed by the grains which have different crystallographic orientation. As a result, it produces an advantageous area where various elements of the solute segregation in steel and metal compounds precipitate out. So, it is not surprising that grain boundary is first to be corroded in some corrosive medium. This kind of corrosion is called intergranular corrosion. The majority of metals and alloys in specific corrosive medium can possibly occur intergranular corrosion.
Crevice corrosion is a form of local corrosion, which can happen in the gap with stagnant solution or on the block surface. The gap can be formed in the joint of metal and metal or metal and non-metal.
General corrosion is a general term which is used to describe the corrosion phenomena occuring on the entire surface of alloy with a homogeneous way. When comprehensive corrosion occurs, the materials will be thinned, even led to failure, due to the corrosion. General corrosion likely occurs in stainless steel in an enviroment of strong acid and strong alkali. However, it doesn't have to worry much about the failure caused by this kind of corrosion, because general corrosion can be forecasted by simple immersion corrosion test or literature consulting.
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