A 7-tank phosphating process is a metal surface preparation method used before powder coating or painting. Its purpose is to remove contaminants, improve corrosion resistance, and provide a surface that helps paint or powder coating adhere strongly.
* Typical 7-Tank Phosphating Process
Tank Process Purpose
Tank 1 Degreasing (Alkaline Cleaner) Removes oil, grease, dirt, and machining fluids from the metal surface.
Tank 2 Water Rinse 1 Washes away the alkaline cleaner to prevent contamination of the next tank.
Tank 3 Derusting / Pickling (Acid Treatment, if required) Removes rust, scale, and oxidation from the metal surface. For clean steel, this step may be skipped.
Tank 4 Water Rinse 2 Removes acid residues after pickling.
Tank 5 Phosphating Forms a zinc or iron phosphate coating on the metal surface, improving paint adhesion and corrosion resistance.
Tank 6 Water Rinse 3 Removes excess phosphate chemicals from the surface.
Tank 7 Passivation / Final Rinse Applies a protective seal that enhances corrosion resistance and prepares the surface for drying and painting.
