3 Suggestions of Powder Coating of Aluminum Die Castings

1. Multi-particles and impurities on the surface of die castings

l Reason:

A. Impurities in curing furnace

B. Dust, clothing fibres, equipment abrasive particles, and dust deposits in the powder spraying system

C. Too many powder additives, uneven pigment dispersion, or too high temperature during powder production, part of the powder has been cross-linked and solidified

D. The powder coating is damp and agglomerates, and the atomization are not well when spraying.

E. There are particles on the surface of aluminum alloy die castings before spraying

F. Too much-recycled powder added and not sieved

G. The coating is sprayed too thinly, and the substrate is difficult to cover if it is mild

l Suggestion:

a. Thoroughly clean the inner wall of the curing oven with a damp cloth and a vacuum cleaner, focusing on the gap between the hanging chain and the air duct

b. Blow the powder spraying system with air before starting work every day, and thoroughly clean the powder spraying equipment and powder spraying room with a damp cloth and a vacuum cleaner

c. Improve powder quality

d. Change warehouse conditions, do not use expired plastic powder and modify coating equipment

e. Clean up before spraying to reduce burrs on aluminum alloy die castings, etc.

f. The recycled powder added is appropriate and needs to be sieved

g. Increase the coating thickness appropriately

2. Serious orange peel on the surface of die castings after powder coating

l Reason:

A. The surface of aluminum alloy die castings are too rough and the coating is difficult to level

B. The powder size is too coarse or its self-levelling is poor

C. The coating is too thin or too thick, if it is too thin, it will show muscular wrinkles, if it is too thick, it will show orange peel

D. Electrostatic shielding, uneven coating thickness

E. The curing temperature is too low and not fully levelled

l Suggestion:

a. Use sandpaper to polish the surface and make the coating thicker

b. Use high-quality powder coatings

c. Master the powder output and spraying time to ensure the appropriate thickness (40-60μm)

d. Improve the spray gun, reduce the electrostatic shielding area as much as possible, or choose a friction spray gun

e. Increase the solidification temperature and extend the levelling time 110-135℃ for the melt levelling area

3. Poor powdering rate

l Reason:

A. The voltage is adjusted too low during spraying

B. The grounding condition of aluminum alloy die casting is not good

C. The resistance of the high voltage generator is too small and the output current is too large

D. The spraying air pressure is too large

E. The hook is insulated and the conductivity is too poor

F. The spray gun is too far away from the aluminum alloy die casting

G. Poor powder performance

l Suggestion:

a. Adjust the voltage to an appropriate value of 60-90KV

b. Add a ground wire to ensure good grounding

c. Increase the resistance of the resistor appropriately

d. Reduce the powder supply air pressure appropriately

e. Clean the hook regularly to make the conductivity good

f. Adjust the spray gun distance appropriately

g. Use high-quality powder coatings