Proper surface preparation is the foundation of any successful metal finishing operation. Whether the end goal is electroplating, powder coating, painting, or passivation, the quality of the final finish depends directly on how well the surface was prepared.
The standard preparation sequence consists of three stages: degreasing (removing oils and greases), pickling (removing oxides and scale), and activation (creating a chemically active surface). Each stage uses specific chemicals at controlled concentrations and temperatures.
Acid pickling with hydrochloric acid or phosphoric acid removes mill scale, rust, and oxide layers. The acid concentration, temperature, and immersion time must be carefully controlled to avoid over-etching, which creates a rough surface and increases metal loss. Inhibitors can be added to reduce base metal attack.