What is passivation of stainless steel
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What is passivation of stainless steel
It is a method to transform the metal surface into a state that is not easily oxidized and slow down the corrosion rate of the metal. In addition, the phenomenon of an active metal or alloy in which the chemical activity is greatly reduced and becomes a noble metal is also called passivation.
Passivation is the process of treating or coating a metal in order to reduce the chemical reactivity of its surface. In stainless steel, passivation means removing the free iron from the surface of the metal using an acid solution to prevent rust. When the surface iron is removed, the other components of the alloy (primarily chromium, often nickel as well) are left behind as a surface layer over the underlying steel. Upon exposure to air, these elements react with oxygen to form an oxide layer that protects the rest of the steel from corrosion.
Passivation of stainless steel can be performed using nitric acid or citric acid. However, there are many reasons that it is better to use citric acid. Many tests have shown that citric acid passivation is more effective than nitric because it only removes iron while leaving all of the chromium, nickel, and other "good" components intact. By contrast, nitric acid will also remove some chromium and nickel along with the iron.
