Jun 10, 2016 0 comment

“We have a situation where a boxed in wrought iron fence has been erected around a harbourside property. The fence has developed a white residue on the wrought iron section but not on the box section. From what we can find out, the box section was hot dipped galv. and the wrought iron was cold gal. primed prior to being powder coated. Is it possible that zinc oxide from the cold galv. primer has leached through the black powder coat, and if this is the case, what can we do about it?”

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“It is certainly possible that the zinc primer is leaching through the powder coated surface, especially if there were pinholes in the powder coating caused by outgassing. This “white rust” is unsightly and may reduce the life of the product, although it is difficult to determine how much the life will be reduced. If you must eliminate this problem entirely, then you must strip all the coating and zinc from the surface and try again, using an alternate zinc preparation.”

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