1、 Different nature
1. Pickling: a method of cleaning oxides and rust on metal surfaces with an acid solution
2. Passivation: the process in which a metal is oxidized by a strong oxidant or electrochemical method to make its surface inactive, i.e. passive.
2、 Different principles
1. Pickling: Generally speaking, parts are immersed in some acidic aqueous solutions such as sulfuric acid to remove oxides or other films on its surface. It is the preparation process of metal parts before other surface treatment(such as plating) or the intermediate step of surface treatment.
2.Passivation: after a layer of oxide film or hydroxide is formed on the metal surface, the increase of applied voltage does not affect the current, the dissolution of metal ions is stopped, and it has corrosion resistance.
3、 Different process
1. Pickling: Generally,Heat-treated steel—→pickling—→water washing—→dipping copper sulfate—→rinsing—→neutralization—→drying.
2. Passivation: before pickling and passivation of metal parts, confirm whether their surfaces are clean. If there are stains or grease, they need to be mechanically cleaned with corresponding organic solvents. Because the stains and grease on the surface will affect the quality of pickling and passivation.
It is important to select the appropriate surface treatment process for customized parts, which will not only affect the overall effect of the product, but also affect the project cost. So professional engineers can provide you with correct and effective knowledge.