Powdercoating galvanised steel

Galv steel that I receive for powdercoating comes in various shades - from dull matte grey to highly spangled shiny almost silver. All suppliers say that the galv isn't passivated - so why the difference?   Can you recommend a book on galvanising for associated industries - something that will give me an idea of the basic process as it may affect a secondary finishing process such as powdercoating.   Looking forward to a reply    

Get in touch with the American Galvanizers Association. They have a number of free publications that are available online about galvanizing and its issues.

Hope that helps...

The condition you refer to is the development of the spangle in the galvanized coating. This is primarily a function of coating thickness and cooling rate of the coating after galvanizing (things like alloy content, etc, also have an effect). The american galvanizers is a good source of information in general, but you may also want to talk with the producing companies as well. If you are buying through a service center (or a mill) you may wish to specify the spangle for your operation. If you are painting or powder coating, a minimized spangle or no-spangle (dull grey) may be desired, but this will be determined by your needs.