If electrochemical reaction or chemical reaction occurs on a metal surface,the stainless steel is uniformly corroded. The part of the stainless steel surface passivation film with weak corrosion resistance forms a pitting reaction due to the self-excited reaction, and generates small holes, and the chloride ions are close to form a strong corrosive solution to accelerate the corrosion reaction rate. There is also intergranular corrosion cracking inside the stainless steel, all of which destroys the passivation film on the stainless steel surface.
So the stainless steel surface must be regularly cleaned and maintained to maintain its gorgeous surface and extend its service life. When cleaning the stainless steel surface, care must be taken not to cause surface scratching. Avoid using bleaching ingredients and abrasive washing liquid, steel balls, grinding tools, etc., in order to remove the washing liquid, rinse the surface with clean water after washing.
For preventing the accumulation of process lubricants or products and/or dirt, mechanical cleaning of scratches and other rough surfaces must be performed by special stainless steel polishing machines.
If the stainless steel is heated to a certain high temperature in the air during welding or grinding, the chrome oxide thermal tempering color will appear on both sides of the weld, the lower surface of the weld and the bottom. The thermal tempering color is thinner than the oxidized protective film and is clearly visible. The color depends on the thickness and can be seen in iridescence, blue, purple to pale yellow and brown. Thicker oxides are generally black. It is due to staying at a high temperature or for a long time at a higher degree. When any such oxide layer is present, the chromium content of the metal surface is reduced, resulting in reduced corrosion resistance in these areas.
Stainless steel products or equipment are sometimes rusted before or during production, which indicates that the surface is heavily contaminated. The rust must be removed before the equipment is put into use. The thoroughly cleaned surface should be inspected by iron test and/or water test.
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