Powdercoating pretreatment for alum and steel
Powdercoating pretreatment for alum and steel
(OP)
Would chromate conversion coating per Mil-C-5541 work ok as a pretreatment for powdercoating on alum?
Would Phosphate coating per TT-C-490 work ok as a pretreatment on Cold rolled steel?
What about Zinc per ASTM-B633, would it work ok as a pretreatment for powdercoating on Cold rolled steel?
If these are not good choices, what would you recommend?
Would Phosphate coating per TT-C-490 work ok as a pretreatment on Cold rolled steel?
What about Zinc per ASTM-B633, would it work ok as a pretreatment for powdercoating on Cold rolled steel?
If these are not good choices, what would you recommend?





RE: Powdercoating pretreatment for alum and steel
2) Yes.
3) Yes, with Type II (with colored chromate).
RE: Powdercoating pretreatment for alum and steel
The iron phosphate will not apply a coating to the aluminum but will increase adhesion and can usually get a few 1000 hours salt spray (depededing on paint and grade of aluminum).
ck1999
RE: Powdercoating pretreatment for alum and steel
For processing aluminum in an iron-phosphating bath, fluoride is added (as aluminum activator).
For steel + zinc-coated steel, a modified zinc phosphate (Type 20 in Appendix II). "This process can also treat up to 15% aluminum" in the work load.
For aluminum + zinc-coated steel, some of the aluminum chromating baths (Types 22 & 23) can be used.
RE: Powdercoating pretreatment for alum and steel
For the steel bracket, we do not have anyone near by that can do the phosphate coating, so the powder coater we plan to use said that he could just sand blast the steel part and that it should be sufficient for a good bond of the powder coating on the part. He says he does that quite often. Does that sound feasible?
RE: Powdercoating pretreatment for alum and steel
Specifying "MIL-C-5541, class 1A, clear" will confuse your metal finisher. Class 1A is normally yellow or gold color (although some trivalents not yet on the QPL are colorless).
RE: Powdercoating pretreatment for alum and steel
Depending on the size of the parts you could look at a high pressure heated spray wand. Which is not ideal but can be used in some instances, having lower start up cost.
ck1999
RE: Powdercoating pretreatment for alum and steel
RE: Powdercoating pretreatment for alum and steel
Try http://www.fremontind.com/index.htm
You may need to contact them or have the powdercoaters do so (the products mentioned don't appear on their website; a corporate account is needed to access product bulletins & MSDS's).
RE: Powdercoating pretreatment for alum and steel
RE: Powdercoating pretreatment for alum and steel
ck1999