The importance of pre-treatment for powder coating

Many people think a thorough clean is enough to ensure excellent powder coating results. But the entire finishing process demands a proper pre-treatment process to make sure the results are the best they can be.

Why pretreat?

The purpose of a powder coating is to provide greater protection to the metal being used. It reduces its susceptibility to rust, corrosion, and damage, increasing its lifespan and range of use. If the powder coating is to do all of this for years to come, it is imperative to make sure you do the correct pre-treatment, so the powder coating lasts.

How does pre-treatment improve powder coating?

Metal pre-treatment helps the powder coating bond more effectively to the metal. It helps it withstand weathering and prevents rust before the coating has taken place. Cleaning is part of the pre-treatment process, but there are other factors that you shouldn’t overlook.

Cleaning

Cleaning the metal surface is step one of metal pre-treatment. The method you use to clean the metal often depends on the type of metal. For example, aluminium and steel are cleaned differently as you have to remove the oxidation layer with aluminium. Castings often need sandblasting to remove any rust that has developed.

Metal cleaning methods include:

• Blasting - This method uses sand or shot to clean up the metal scale, laser scale, rough welds, or heavily rusted steel. You can also use it to remove the previous coating for refinishing. However, one downfall is that it doesn’t fully clean the metal of oils and other contaminants.
• Washing - Pressure washing, automatic washing, or dipping occurs with specially formulated soap. It is one of the most effective ways to clean metal before the next stage, and it removes oils and other contaminants found on the metal.
• Wiping - Solvent wiping is another method to clean the metal and remove surface oils and contaminants. However, since you wipe the metal with rags that become saturated with the oils you are trying to remove, it can be an inaccurate way to clean.

After this, it is time for step two - etching or phosphating.

Treatment

Choosing which process to use, out of etching or phosphating, largely depends on the quality of the metal, customer specifications, and metal performance lifespan. If the metal were used outdoors, for example, it would require a high-quality treatment process to ensure it can survive the elements for years to come.

Etching is best suited to smooth metals - for example, aluminium. It removes oxidation and corrodes the surface of the metal, making it rougher, providing a better surface for the powder coating to cling to. This ensures a more successful and longer-lasting powder coating.

Phosphating is more common than etching. It uses an acidic product to treat the metal surface, making it rough to promote the adhesion between the metal and powder coating. This process vastly increases the resistance to corrosion and is a popular pre-treatment method.

Skipping proper pre-treatment would cause a poor-quality metal finishing, reducing the value of your investment. Therefore, it is always important to go through the correct pre-treatment process.

At Tomburn, we protect the integrity of your powder coating through accurate and effective pre-treatment services. We specialise in the pre-treatment of aluminium, mild and galvanised steel, zintec, and ferrous and non-ferrous castings. If you want more information about our pre-treatment services, or you need a quote, get in touch with us simply by calling 02392 692 020.