Under what circumstances? Is the nominal coating thickness the same? In general, galvanneal will generate a dull reddish-brown appearance when exposed to corrosive environments, especially near the sheet edges, that is different from conventional iron oxide (red rust). For this reason, if the cosmetic appearance is a requirement for the application, hot dip or electrogalv are used instead. Galvanneal is best for applications that will be subsequently painted and/or spot welded.
You probably don't know what galvannealing is. You take hot-dipped galvanized steel and immediate move it into a furnace to cause diffusion of the zinc and iron atoms. This creates a coating that has improved spot weldability and paintability. If you aren't spot welding it, and/or aren't painting it, you should stick with hot-dipped galvanizing.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
I agree with CoryPad galvanealed is a galvanized product with a heat treating process added. Galvnealed was orginally created for a paintable galvanized material. The amount of corrosion protection will be based on the environment the material is exposed to. The same applies to galvanized materials. The worse environment there is reduce protection.
The amount of protection is based on the thickness of the zinc surface and if you were to compare a commercially prepared galvanized/galvanealed product versus a hot dip beam you would see more protection on the beam is greater as the process of hot dipping normally produces a thicker zinc coating.
