A 7-tank cold phosphating process is a metal surface treatment system used before painting or powder coating. It removes contaminants, improves corrosion resistance, and creates a surface that helps paint adhere better.
1. Degreasing - Alkaline degreaser (caustic soda, surfactants, builders) Removes oil, grease, dirt, and machining fluids.
2. Water Rinse - Clean water Washes off degreaser residues.
3. Derusting - Pickling Hydrochloric acid (HCl) or sulfuric acid with inhibitor Removes rust, scale, and oxides from steel.
4. Water Rinse - Clean water Removes acid residues before phosphating.
5. Cold Phosphating - Zinc phosphate solution with phosphoric acid and accelerators Forms a phosphate coating that improves paint adhesion and corrosion resistance.
6. Water Rinse - Clean water Removes excess phosphate chemicals.
