Unlike liquid paint, powder coating is sprayed onto a surface and then heated until the powder particles melt together. This process makes powder coating much harder than paint. This hardened paint film makes for an easy surface to clean, without damaging the finish. Water can sometimes get on a powder coated surface and then evaporate. After it evaporates, the minerals in the water remain on the surface, forming hard water spots. An acid-based cleaner works well for hard water spot removal.
Spray the hard water spots with a lime scale remover that is high in phosphoric acid. This solution can be found at janitorial supply stores. It has a higher percentage of acid than the grocery store cleansers.
Allow the lime scale remover to sit on the hard water spots for 15 minutes.
Scrub the treated areas with a white, nylon scrub pad until the water spots are removed. Repeat the process for extremely stubborn water spots.
Rinse the scrubbed area with water to remove all traces of acid. Wipe the area dry with paper towels to avoid more hard water spots.
Always follow the manufacturer's warnings and recommendations before applying phosphoric acid solutions to any surface.