Zinc Anodized Electroplated vs Hot Dip Galvanized
I came across some info on the potential of zinc anodizing as a lasting finish over zinc electroplated or over hot dip galvanized steel materials. Its potential has been stated to last thousands of hours over ASTM B117 [link by ed. to spec at TechStreet] salt spray test (as a guide tool).
However, it wasn't mentioned if this thousands of hours are over the thinner coating of electroplating or the 10 times thicker coating of hot dip galvanizing.
Does the corrosion protection of the zinc thickness of hot dip galvanizing (with or without chromate) be ever equal to the potential of zinc anodized electroplated steel (with or without chromate)?
If yes, how thick should the electroplating coating be to be zinc anodized in order to reach an equivalent of 2,500 hours in B117 salt spray test? theoretically?Anthony Austria
The only references I've read related to anodizing of zinc diecast items, rather than zinc coatings on steel, Anthony. There is, to my knowledge, little use of anodized zinc and little published case histories, and I don't know if any information exists that will answer your question. I think a development program is needed. Note that the voltages required for zinc anodizing are easily lethal, so it can't be done in the usual plating/anodizing tank with exposed busbars.
Ted Mooney, P.E.
Pine Beach, New Jersey
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