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Overview of the Five Most Common Surface Treatment Processes and Anticorrosive Coatings
Added Time:Jul 26, 2026
When steel products are exposed to the atmosphere for a prolonged period or subjected to heat treatment, their surfaces become covered with rust or black oxide scale, which consists of various iron oxides. These oxides must be removed in advance before any surface treatment is carried out. Methods include manual derusting, mechanical derusting, and abrasive blasting, among which treatment with various acidic reagents is the most widely used method for rust removal. This treatment essentially cleans the metal surface by dissolving the rust with acid and mechanically dislodging it through the action of hydrogen gas generated by the reaction between the acid and the metal substrate during treatment. The process of removing large amounts of surface oxides with acid is called strong pickling, or acid pickling, while the process of removing thin oxide films on the surface that are not readily visible to the naked eye is called light pickling. Sometimes an electric current is also applied during the pickling process, in which case it is called electrochemical pickling. Electrochemical pickling is used for both strong and light pickling. Light pickling is generally carried out after strong pickling and before the workpiece enters the electroplating tank. After this process, metal products must not remain in the atmosphere for too long, and in particular, their surfaces should not be allowed to become dry. To ensure that the pickling process proceeds smoothly, oil must be removed beforehand; otherwise, the acid cannot come into sufficient contact with the metal oxides, inhibiting the chemical dissolution reaction.
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