Question on Phosphate Prep

[mdeluca]

I am real new to this so please forgive my naivete.

I hear that a phosphate wash is a good idea. What is the difference between a phosphoric acid based prep and etch and iron phosphate.

Is the process the same with either.

I found a phosphoric acid based prep and etch at Home Depot and am wondering if I can use it.

Thanks.

[jbotti1]

I have another question to add to yours (sorry). Do you phosphate, dry, clean with acetone, shoot Or do you phosphate, dry, shoot?

[red911]

Any responses from you pros out there?

What I do is use a Caswell cermic heater to get the solution temp up to 180 degrees F and preheat the part to 200 degrees F. Dip the part into the phosphate solution, air dry with an air nozzle and powder coat the part then.

Tom

[robsrod]

Zinc phosphate actually grows a crystaline sturcture on the surface of the metal which aids in the adhesion of the powder.

I usually wash down using a pressurized pump sprayer with phosphate. Let dry or stick in the oven for a short period at 150 or so the pull out and coat. I have also used this method as a dip, but wastes to much liquid.

[bzer1]

This is from a previous post. The issue with Iron phosphate is that it needs to be heated to work properly.

Hot tank-Parts washer

There are many prep solutions out there that will do the job. Be very careful what you buy, as the spent phosphate can be very tricky and quite expensive to get rid of. Most tell you that their formula can be poured right down the drain...this in most cases is true for the virgin solution but not for used material. Iron phosphate is a conversion coating generally used as a rust inhibitor. It does promote adhesion but careful prep and cleaning will also net good results. If you're not opening a shop or are only doing limited paying work I would say your best bet is to spend your money on a good blast cabinet and maybe some acetone or other needed supplies. Building a phosphating tank or prep station can be very costly and unnecessary for occasional powder coating. If, in the future you decide to upgrade and open a full time shop you would most likely add a good sized prep station.

BTW: If you acetone wipe steel after phosphating, it will flash rust. You shouldn't need to do anything after phosphating. Just shoot it and cure.