Power Coating Adhesion and Outgassing on Galvanized Steel

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  • Topic: Corrosion, Hot-dip galvanizing, Zinc
  • Pages : 2 (652 words )
  • Download(s) : 391
  • Published : February 17, 2013
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Q

I am contemplating powder-coating some hot-dip galvanized steel to further increase its corrosion protection. I have heard some rumors regarding the adhesion of powder coatings on galvanized steel. Apparently the adhesion is compromised due to the zinc coating outgassing. Is there any truth to this? Is there anything I can do to prevent outgassing of the zinc coating? lightly-acidic solution will remove oxides from the surface as well as slightly etch the steel surface, providing a better surface profile for top coating to adhere to. Proprietary solutions are available that are designed to work effectively on galvanized or other zinc surfaces.

ASK DR. GALV

Yes, outgassing of the zinc coating can occur when applying a powder coating over galvanized steel, which could potentially affect the adhesion and continuity of the coating. However, it can be prevented if the proper surface preparation techniques are used in conjunction with good powder application practices.

A

Pre-baking in a drying oven can also reduce the potential for the The key to achieving good adhegalvanized coating to outgas. This sion between powder coatings and process will aid in the expulsion of galvanized steel is surface preparaany trapped air or water in the tion. The surface must be entirely coating as well as ensure that the free from zinc oxides prior to powsurface of the steel is free from der coating. Any zinc, or other any moisture. The pre-baking metal oxides, that remain on the oven should be operated at higher surface of the galvanized steel can temperatures than the curing oven; potentially retain air or moisture. this temperature is typically 55 F Upon heating during the curing (30 C) higher than the curing Pipes color-coded using powder coating; stages of the powder application, oven. If the galvanized steel is run a common application. the oxides may release water vapor through a phosphate wash prior to or air, which can expand and penetrate the powder coating,...
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