Phosphating

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Phosphating is a process that is used to coat metals, such as iron and steel. In this process, a phosphate of another type of metal, such as zinc, is coated onto a piece of iron or steel to protect it from corrosion. By phosphating a piece of metal, the metal is protected from rust and prepared for other treatment processes, like painting. The phosphate layer creates a stable base for the next layer, such as paint or powder coating, to be applied.

The phosphates are placed in a solution of acid, which causes them to dissolve and create a bath of phosphate coating. Then the metal part is immersed in the phosphate acid bath. This creates a chemical reaction that causes a layer of phosphate to adhere to the surface of the metal.

The base for the phosphate coating bath is a solution of phosphoric acid. The phosphate of choice is then dissolved in that solution. When the metal piece is immersed in the solution, the metal reacts with the acid solution. As a result, the pH of the solution increases, and the phosphate is deposited onto the metal. The phosphate coats the metal in an even, uniform layer. Zinc, manganese, and iron are the most common types of metals used in phosphate coatings. Zinc and manganese offer better resistance to corrosion than iron phosphate. All phosphates are fairly porous, so they do not provide complete protection from rust. They serve primarily to provide a stable base for an additional process or coating. For additional protection from corrosion, oil is often applied over a phosphate coating. Because the layer of phosphate is somewhat porous, it absorbs the oil, forming a barrier to moisture. An additional layer of coating, like a sealant or lubricant, can be applied over the top to help prevent corrosion and reduce friction.

Metal parts are often coated with phosphate before they are painted in order to provide a base that will adhere to the paint. The porous nature of the phosphate makes it bind with the paint better than bare metal.

Phosphating is also used as an initial treatment process before rubber bonding processes because it enhances adhesion.

Springco Metal Coating offers three types of phosphating treatments, including the following:
  • Zinc phosphate with oil;
  • Zinc phosphate without oil;
  • Calcium modified zinc phosphate.
  • These options are available for both rack and barrel.

Springco Metal Coating provides a variety of metal coating services. We have been an industry leader for more than 25 years. Springco consistently provides the highest in quality products and service at affordable prices. We are able to comply with the rigorous standards of the automotive, military, truck, heavy equipment, and appliance industries.

To learn more about how Springco Metal Coating can help your business, get in touch with us today.

Typical coating weights of macro-crystalline phosphates is 950 – 2,000 mg/sq ft & 150-450 mg/sq ft for micro-crystalline phosphates.








Springco Metal Coating has the following Phosphating options for both rack and barrel:


Macro-crystalline Zinc Phosphate & Oil (dry to the touch)

Used for corrosion protection –72-96hrs of Salt Spray

Macro-crystalline Zinc Phosphate & Dry (no oil)

Used for corrosion protection –24-48hrs Salt Spray

Micro-crystalline Calcium Modified Zinc Phosphate

Used to promote better adhesion of paints & rubber bonding


Springco Metal Coating can coat parts with a profile of 72” x 24” x 36” and up to 1,000#s



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