Among the passivation film layers formed after galvanizing, which one – the white passivation layer or the colored passivation layer – has better corrosion resistance?
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Among the passivation film layers formed after galvanizing, which one – the white passivation layer or the colored passivation layer – has better corrosion resistance?
Colored zinc is better; the salt spray test shows this clearly
For the passivation film layer after galvanizing, colored passivation offers better corrosion resistance than white passivation. This is because during the dulling treatment, a layer of the already formed colored passivation film is dissolved in the bleaching solution, turning the colored passivation film white. Since the white passivation film is thinner than the colored passivation film, its corrosion resistance is reduced.
The best corrosion resistance is provided by the military green coating; colored dull coatings come next, followed by blue coatings, with white coatings having the worst performance. In fact, white is just blue with its color made very light~~~~~ That’s why blue-white passivation is often used to explain it.