There are lots of advantages to powder coating; the electrostatic process is known for providing a cost-effective and durable finish. It is also a more sustainable process than wet paint, as it uses less water and fewer chemicals. But a question which is often asked is:
Powder coating can mask minor surface finish irregularities to some extent. However, more severe defects, like oil contaminations, cutting fluids, scratches, pinholes, flaking/chipping, and uneven corners, cannot be eliminated completely, impacting coating performance.
At Powdertech, for one of their clients, they replicated some typical metal surface defects on their parts on ‘Aluminium test coupons’ to fast-track the process of determining if surface defects, such as oil contamination and deep scratches, are covered by powder coating. This enabled them to design a finishing spec for their machinists.
For this purpose, four aluminium test coupons were used to test the powder coating process over surface defects.
Coupon A – A defect-free, benchmark piece that replicates an ideal part before the powder coating process begins.
Coupon A is kept to compare coupons B, C, and D, which have surface defects like deep surface scratches, shallow scratches, and oil contamination, respectively.
The result
Powder coating will not hide deep existing surface imperfections, which are easily visible. The use of fine-textured powder, as selected by the customer for their project, has a better chance of covering small scratches in the metal as compared to gloss or matte finish powders. Nonetheless, as shown below, it cannot cover all defects.
*For this project, fine-textured powder was used as per the customer’s requirement.
Coupon B – The powder coating does not cover the scratches; instead, it follows the profile of the damage without filling it in. This can be easily seen and felt on the metal surface.
Coupon C – More likely to fill in the scratches, but witness marks are visible.
Coupon D – A shadow in the powder coating surface can be seen, and the powder has not adhered to the surface, resulting in failure of the coating. The coating is likely to flake off and fail its purpose.
Powdertech Surface Science, Bicester.
Customers rely on Powdertech to ensure the coating process runs more smoothly during production with fewer delays. They stay closely involved at every stage to prevent delays, costly reworks, and production downtime, as early detection of surface defects ensures the coating performs as per the spec requirements.
