Common Defects: White Spots

White spots are often found on colored work. The shape (round, irregular) and location of the spots are good clues.


Could be due to the metal e.g. Jig plate, Mic 6, Castings. Best course is to include a neutralization rinse after anodizing. White spots are often due to foreign particles from the air or rinse adhering to the coating and acting like a mask in the color bath. Etch mist in the air can be at fault, or mould particles in the post anodize rinse. Often a white spot is actually a popped blister and no coating is present at all (this should be checked). Blisters of this kind are usually metal related but they can be due to an interruption in the anodizing power. Blisters on electrolytic color (usually cobalt and nickel) can be due to high coloring voltages, and bath contaminants.


These are most often due to pits or micro-folds in the aluminum that entrap anodize acid and slowly release it in the dye bath. The usual practice is to focus on rinsing after anodize. You could try a warm rinse, a nitric rinse, a neutralization rinse, or any combination.

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