What is phosphating?

2023-07-07T07:50:08+00:00

Phosphating is a conversion coating for treating the surface of iron and steel components, where metal-phosphate layers are formed on the base material.

It is mostly used as a pre-treatment before we apply another means of protection, usually coating or painting. As well as protecting against corrosion, it reduces friction between sliding components – we’re all about protection and performance.

In its basic form, phosphating involves immersing a component in a solution, which converts the surface of the metal into a layer of microscopic phosphate crystals.

It’s commonly applied to steel, iron and other ferrous metals.

The process usually involves several steps:

1 - Cleaning: the metal surface is thoroughly cleaned to remove any dirt, grease, rust or other contaminants. This step makes sure the phosphate coating adheres properly.

2 - Activation: in some cases, an activation step is performed to encourage the phosphate layer to form. This can involve the use of an acid-based solution to remove any oxide layers and provide a clean surface for the subsequent phosphating process.

3 - Phosphating: the metal is immersed or sprayed with a phosphating solution, which typically contains phosphoric acid and various additives. The specific composition of the solution will depend on the desired application and the metal being treated. The metal surface reacts with the phosphating solution, resulting in a layer of phosphate compounds forming. This layer typically consists of various phosphates, such as iron phosphate or zinc phosphate.

4 - Rinsing: after the phosphating step, the metal is rinsed with water to remove any excess solution or loose particles.

5 - Drying: the metal is dried to remove moisture from the surface, typically through air drying or using a heated drying process.

The layers created are porous, absorbent and suitable as a pretreatment for subsequent coatings.

Why would you use phosphating?

Phosphating is used as a surface treatment process for several reasons:

Corrosion protection: phosphating forms a protective layer on the metal surface, which significantly improves its resistance to corrosion. The phosphate coating acts as a barrier, preventing direct contact between the metal substrate and corrosive agents such as moisture, chemicals or environmental pollutants.
Surface preparation / enhanced paint adhesion: phosphate coatings provide a textured surface with increased surface area, which promotes the adhesion of subsequent coatings, such as paint or low friction coatings. This helps the coatings to adhere better and ensures better durability and longevity of the painted or coated surface.
Better lubrication: phosphate coatings can reduce friction and wear between metal components. This is particularly useful in applications where sliding or moving parts are involved, such as in automotive engines or industrial machinery.
Aesthetics: in some cases, phosphating can be used to achieve a desired aesthetic appearance.
Cost-effectiveness: phosphating is a relatively cost-effective surface treatment process compared to some other alternatives. It can be easily implemented in large-scale industrial applications and offers good overall performance for the investment.

Overall, phosphating is a versatile and widely used process that provides several important benefits. It helps to enhance the performance, durability, and aesthetics of metal components in various industries.

Is it right for your needs? Get in touch with the team here at Nexus and find out.

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