Operating a Processing and Manufacturing Facility

Tips on Ensuring Effective Powder Coating of Metal Substrates

19 June 2017 by Todd West

Powder coatings are preferred over other finish types in several metal coating applications due to their superior resistance to rusting, scratching, fading, chipping, and other destructive elements. Unlike a paint protective coating, which is applied in liquid form, powder coating is electrostatically applied onto the substrate as a dry powder using a spray gun, thus eliminating the need to use a solvent. The final outcome is a finish similar to that of liquid paint, but one that can last longer. The quality of powder coats may vary from project to project, depending on the effectiveness of the application process. 

Here are some tips you can follow to ensure your powder coating job is performed successfully. 

Ensure proper electrical earthing of the substrate

When an electrostatic spray gun is used for powder coating applications, large quantities of electrons (negative charges) are transferred from the powder particulates to the substrate. The powder particulates become negatively charged because they are ionised by the air around the nozzle tip of the spray gun. So as to ensure the powder adheres well, electrical grounding of the substrate is critical. Otherwise, the powder-coated surface will quickly develop a strong negative charge, which will repel the negatively charged powder being released from the spray gun. As a result, it becomes difficult to apply uniform coats of thick powder onto the substrate.

To apply a thick, uniform coat of powder onto a metal surface, it is imperative to partially neutralise the powder via electrical earthing. If optimal neutralisation is not achieved fast enough, the powder-coated substrate will develop a strong positive charge, which in turn, repels positively charged powder from the spray gun. Insufficient earthing is easy to detect as it leads to little or no powder buildup around the object being coated.    

Ensure the quality of compressed air is good

The compressed air supplied to spray guns should be dry and free of contaminants like water and oil. If the quality of the compressed air is compromised, the electrostatic charging properties of the powder can be affected. This can tarnish the visual appearance of the coating. It is also important to measure the relative humidity level within the jobsite. 

Ensure quality of air in the working area is good

In addition, relative humidity within the working area should be optimised to ensure a faster and more uniform accumulation of the powder coats. There are lots of easy to use tools like a psychrometer for measuring relative humidity. 

If you don't think you are up to the task, it is best to let a professional work for you. 

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