What more can we do to improve the smoothness of power coating on diecast aluminum housings

Achieving a smooth finish on diecast aluminum housings often comes down to managing the physics of the powder particles and the chemistry of the aluminum alloy. 

The smoother the aluminum surface underneath, the smoother the coating finish on top. Before coating, ensure the diecast aluminum casing is polished well at first. Any pitting or scratches in the aluminum will be magnified by the powder.

Use a high-quality chemical de-oxidizer to remove the invisible oxide layer that prevents the powder from flowing out evenly. Aluminum castings often trap air. Pre-heat the parts to a temperature higher than your curing temperature for about 20–30 minutes. This forces the air out before you apply the powder in order to prevent bubbles.

Also, you need to refine the application physics by managing voltage well. Too much voltage causes Back Ionization, where the powder repels itself, creating a grainy texture. Drop your voltage at last to allow a tighter, more uniform build. Check the grounding because poor ground can result uneven thinkness. Micro adjustment of flow on the air is also necessary, or the power might hits the aluminum surface too hard and bounces.

Not all powder particles are created equal. Ask your supplier for “fine”powder. Smaller and uniform particles will melt more evenly. Some powders are formulated with extra “leveling agents”. They can reduce the surface tension of the paint during the melting phase. Just choose powders with a lower “melting viscosity” for smoother coating. A slow ramp-up temperature helps better leveling and coating, which will result in final compact and smooth surface on aluminum housings.