Salt spray test: test by salt spray test equipment to create artificial saline fog environment conditions to assess the corrosion products or metal materials. Salt fog corrosion of metal material surface is due to chloride ion penetration of metal containing surface oxide layer and protective layer and the internal metal occurs due to electrochemical reaction. At the same time, chloride ion containing certain hydration energy, easy to be absorbed to replace the oxide layer on the metal surface oxygen in pore, fracture and the crowding, insoluble oxides into soluble chlorides, the passivation state surface becomes the active surface. Due to the adverse reactions are very bad.
Intergranular corrosion: because of the difference between the grain surface and internal chemical composition and the grain boundary impurities or the existence of internal stress. Corrosion of metals and alloys after surface remains metallic luster certain, do not see signs is destroyed, but the binding force between grains decreased, poor mechanical properties, could not withstand the strike, so it is a very dangerous erosion. Usually appear in brass, aluminum alloy and stainless steel, nickel base alloy. Stainless steel weld intergranular corrosion is an important problem in the chemical industry.
Intergranular corrosion: because of the difference between the grain surface and internal chemical composition and the grain boundary impurities or the existence of internal stress. Corrosion of metals and alloys after surface remains metallic luster certain, do not see signs is destroyed, but the binding force between grains decreased, poor mechanical properties, could not withstand the strike, so it is a very dangerous erosion. Usually appear in brass, aluminum alloy and stainless steel, nickel base alloy. Stainless steel weld intergranular corrosion is an important problem in the chemical industry.