Haziness

Potential Cause

Back ionisation occurring.  Where voltage is too high, or where the gun nozzle is too close to the part the powder layer reaches a saturation point, beyond which additional coating is deflected off the surface and eventually causing the deposited film to jump off the part, creating craters and star-like patterns in the powder film.

Solution

Check the electrical earth and that the grounding points are clean.  Decrease the voltage by 10-20 kV.  Move gun further away from component.

Potential Cause

Spray gun settings:

• Gun distance from part too great or small
• Uneven powder transport
• Poor charging
• Poor electrical earth.

Solution

Test and optimise gun settings

Potential Cause

Micropinholing from gassing caused by

• moisture in the local environment, airline or substrate;
• a porous substrate.

Solution

Ensure that humidity levels are controlled and that the air line is clean and dry.  Check that the substrate has not trapped air or moisture by pre-heating it slightly above the curing temperature of the coating, allowing to cool then powder coating.

Potential Cause

By-products of resin manufacture depositing on surface because their energy is too low to sublime off the substrate. Caused by

• Oven curing temperature too low
• Heavy substrates
• Prolonged exposure to elevated temperatures, in particularly ~150-160 Celsius.

Solution

Ensure metal temperatures reach the recommended curing temperature. Whilst coatings will cure at reduced temperatures when given a longer cure, this may cause severe blooming.  Do not leave products to cool in a box oven. Once the curing cycle is complete, open the oven doors and remove the work.

Potential Cause

Insufficient air circulation in the oven

Solution

Increase air circulation

Potential Cause

Contamination on the surface because of incompatible powder coatings from different manufacturers

Solution

Use only powder coatings from one manufacturer at the same time in an oven.  Contact us.