What is a phosphate coating?

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phosphate coating is a type of metal treatment, especially iron and steel, in which a layer of other metal phosphate, such as zinc, is applied to ensure corrosion protection. The phosphate coating The steel part provides an inert layer to help prevent rust and provide a stable base for applying other coatings such as color. The phosphates are dissolved in acidic solution and when the metal part is immersed in phosphate acid, a chemical reaction leads to cause phosphate to be placed on the surface.

phosphoric acid solution is used as a base for a phosphate coating bath. The desired phosphate for the coating is dissolved in the solution. When a piece to be covered is immersed in solution, acid reacts with metal. This causes the pH of the solution immediately rising around the metal piece, resulting in the precipitation of phosphate from the solution and to the metal. Phosphate is bound to The metal in a layer of relatively even thickness regardless of the shape of the part.

Primary metals used in phosphate liners are zinc, manganese and iron. Zinc and manganese phosphates provide stronger corrosion resistance than iron phosphate, but because the phosphate layer is somewhat porous, none of the three phosphates is a perfect barrier for rust or other corrosion. Instead, the phosphate coating provides a base for additional coatings or treatment.

oil is often applied to a phosphate coating as further corrosion protection. This works well for rust prevention because the porous phosphate coating absorbs oil and together create an effective barrier. This type of coating is often known as the P&O coating, for phosphate and oil. Other coatings are often applied to phosphate coatings, especially seals and lubricants. These types of treatment are effective in preventing corrosion and reducing wear of moving parts by reducing friction.

The metal parts to be painted are often coated with phosphate in preparation for color application. In these cases there is resistance toSecondary corrosion to the characteristics of the coating, which is particularly useful as a base layer for the color to stick. The porous phosphate coating absorbs and binds to the color much more efficiently than it would be on the bare metal.