Summary for electro-galvanneal Discussion
electro-galvanneal is the key specification question in this thread: Gerry Maynard asks whether the term is correct for a part currently called out as CS Type B per ASTM A653, and whether a separate standard is needed. He understands galvanneal as hot-dip galvanized steel that is then heated to form a zinc-iron diffusion layer, but wonders if electro-galvanneal is simply electro-galvanized steel with the same extra heating step. Toby Padfield says the hot-dip galvanneal understanding is correct, but notes that electroplated sheet is different: the bath chemistry is adjusted so zinc, zinc-iron, or zinc-nickel coatings are deposited directly, so a later furnace step is not required. He points to ASTM A879, ASTM A917, and ASTM A918 as the relevant electroplated steel sheet specifications rather than ASTM A653.
Q. I am trying to properly specify the material for a part we now call out as CS Type B per ASTM A653, which we call “electrogalvannealed” and I think this is incorrect. I have seen galvanneal defined as hot-dip galvanized with the extra heating step to form the zinc-iron diffusion layer. Is electro-galvanneal just electro-galvanized with the same heating step added? If so, then it seems ASTM A653 would not be the correct specification, so is there a correct one?
Gerry Maynard
Mechanical Engineer – West Greenwich, Rhode Island, USA
July 20, 2010
A. You have the correct understanding of hot-dip galv and the subsequent galvanneal process. Things are a little different though when the coating is applied by an electroplating process rather than by immersion into molten metal. The bath chemistry is specifically adjusted so that zinc, zinc-iron, or zinc-nickel coatings are directly deposited, which means that a subsequent furnace is not required. Electroplated steel sheet specifications include ASTM A879, ASTM A917, and ASTM A918.
Toby Padfield
– Michigan, USA