Normally, powder coating has a slick surface which does not allow paint to stick. Sanding it down carefully will enable you to paint on it effectively. Wipe down the area you will be painting with an appropriate solvent cleaner. Finally, rinse it down with warm water, then allow it to dry.
How do you touch up powder coated aluminum patio furniture?
https://www.youtube.com/watch?v=I64WZlv0dlA
What kind of paint will stick to powder coating?
Epoxy-based paints will stick to most surfaces, but may be costly and limited in the colors available. Enamel paints may be a better option cost-wise and should adhere well to primers needed for metal alloys.
Can you paint over powder coating?
Normally, powder coating has a slick surface which does not allow paint to stick. Sanding it down carefully will enable you to paint on it effectively. Wipe down the area you will be painting with an appropriate solvent cleaner.