Phosphate coating for metals, especially iron and steel, layers phosphate over another metal substrate, such as zinc, to protect against corrosion. Phosphate coating a steel part provides an inert layer that will help prevent rust and provide a stable base for applying other coatings like paint.

Phosphates are dissolved in an acidic solution. When the metal part is submerged in the phosphate acid bath, a chemical reaction causes the phosphate to be deposited on the surface. The phosphate binds to the metal fairly even in thickness, regardless of the part’s shape. Oil is often applied to a phosphate coating to further protect against corrosion. This works well for preventing rust because the porous phosphate coating absorbs the oil, and together, the two create an effective barrier. Nico Products provides Zinc Phosphate and Manganese Phosphate options.