Pre treatment options for Aluminum Alloys

[RBobroski]

Hi all,

I was curious as to what the suggested pre-treatment options are for Al Alloys prior to powdercoating? We primarily use 6061-T6/T6511 and 5052-H32, and I currently am calling out a 5 stage Iron Phosphate pre-treatment but upon doing some research I am seeing a lot along the lines of a Chromate conversion coating. What are the pros and cons of both? I assume Hexavalent Chromium would be more expensive due to the toxic issues with it, but I also see non-Hexavalent containing Chromate conversions; what does this entail? these parts are for structural members of vacuum systems, and while they aren't going to be seeing a constant salt spray or anything they do have the potential to be operated outside for the majority of its use near marine environments.

 

[swall]

The Powder Coating Institute lists several pre-treatment options: Chrome phosphate, Hexavalent chromate, Trivalent chromate and some titanium and zirconium chemistry with a polymer. To get better direction for your application, contact one of the treatment chemistry suppliers such as Henkel.

 

[CoryPad]

You should use a hexavalent chromium free pretreatment. Some options include Alodine from Henkel, Iridite from MacDermid, and Gardobond and Oxsilan from Chemetall.