304 stainless steel (new standard 06Cr19Ni10 steel, old standard 0Cr18Ni9 steel) due to its good toughness, plasticity, weldability, corrosion resistance, and no magnetism, widely used in petrochemical, metallurgical machinery, aerospace, food processing, instrumentation, household appliances and hardware manufacturing and other industries at normal temperature and low temperature.
304 austenitic stainless steel in the atmospheric environment has excellent corrosion resistance is due to the surface of a layer of Cr passivation film, if the material itself inclusion, and the environment cause local corrosion conditions may lead to material corrosion, a small effect on the product’s appearance, big become later use of safety risks.
A large number of corrosion points appear on the surface of a batch of 304 stainless steel fasteners, from the material organization, inclusion level, crystal boundary corrosion performance, corrosion point morphology, corrosion location composition, rust layer composition, and other aspects.
According to the relevant literature, 304 austenitic stainless steel corrosion is generally divided into the following categories: first, the precipitation of the grain corrosion in the grain boundary and the corrosion caused by the surface corrosion of the material surface resulting in the local corrosion; third, the stress corrosion in the presence of ions with strong penetration capacity such as chloride ion.
A large number of corrosion points appear on the surface of a batch of 304 stainless steel fasteners, from the material organization, inclusion level, crystal boundary corrosion performance, corrosion point morphology, rust occurrence location composition, rust layer composition, and other aspects.
According to the relevant literature, 304 austenitic stainless steel corrosion is generally divided into the following categories: first, the precipitation of the grain corrosion in the grain boundary and the corrosion caused by the surface corrosion of the material surface resulting in the local corrosion; third, the stress corrosion in the presence of ions with strong penetration capacity such as chloride ion.
The summary for the corrosion cause of 304 stainless steel surface is as follows: 304 stainless steel solid solution treatment is sufficient, and will not cause grain boundary corrosion because of carbide precipitation.
The corrosion depth of severe rust is 30 μ m, and the rust will not continue to expand in the atmospheric environment. The material surface inclusion is the origin point of rust, but the inclusion exists in the surface layer, after grinding and removal, it can avoid rust occurrence.
According to the causes of corrosion, three measures are taken: first, to strengthen the control of raw material procurement process to reduce the content of S element in the finished product; second, for cleaning before passivation, it is best to wash with weak alkaline solution; for the third product, the grinding surface is about 30 μ m.
304 stainless steel valve surface corrosion cause
