Zinc Chromate vs Zinc Phosphate & Other Etching Primers

[North Beach]

So the question is pretty simple. Could I use Zinc Phosphate in leiu of Zinc Chromate as my etching primer on a bare aluminum hull. The chromate is fairly hard to come by and sometimes the local (160 miles round trip) marine store only has the phosphate.

Also, what about your standard rustoleum etching primer? I'm on my third hull and the ZC gets a tad expensive.

I'll be using Petit's Easypoxy undercoater and then the Easypoxy over that.

I sure would like to be able to just run up to the local Home depot and buy a couple qts of etching primer when I need it.

 

[kilowatts]

Re: Zinc Chromate vs Zinc Phosphate & Other Etching Primers

Hi NB:

I'm by no means an expert on the undercoating of aluminum but when I repainted my outdrive and other marine aluminum parts I started to read up on the properties of ZC and ZP. As far as I remember only the ZC does an adequate job of etching in an uncontrolled situation such as shade tree guys like us are capable of. Generally speaking though I believe that we tend to put too much ZC on the raw aluminum. My understanding is that you only need a thin cover and only on the raw metal as it has no effect on the existing paint. Further, there's no point in removing all the existing factory applied paint as they are able to do a much better job of preparation than we are, simply prepare and apply the new coat over top. I think my message is that ZC is the one to choose and to cut down on cost, spot apply a thinner coat on the raw metal only after the correct preparation, degrease, wash down, 50/50 vinegar etc.
I hope this helps!

kilowatts

 

[ezmobee]

Re: Zinc Chromate vs Zinc Phosphate & Other Etching Primers

I got this at Pep-Boys pretty reasonably http://www.duplicolor.com/products/selfEtchingPrimer/

Dupli-Color? Self-Etching Primer etches and primes bare metal in one step, making it ideal to use as the first step in all automotive priming projects and for use on spot repairs. A high-quality formulation allows for maximum adhesion under all types of automotive finishes on plastics, fiberglass, bare steel, aluminum and stainless steel surfaces.

 

[erikgreen]

Re: Zinc Chromate vs Zinc Phosphate & Other Etching Primers

I've tried the SEM brand self etching primer... light gray color.

I dunno about steel, but on my aluminum outdrive it worked only a little better than plain gray primer.

I also tried the Rust-Oleum aluminum primer, it's ok but not meant for in the water situations, plus it's latex, so no go there.

Next time I'll either get the manufacturer's brand name primer or ZC.

Erik

 

[North Beach]

Re: Zinc Chromate vs Zinc Phosphate & Other Etching Primers

Thanks guys! I know I used way too much zc on the LL. Maybe I'll just leave the side paint on my latest project and just go over it. I got a little carried away with the stripper today on the bottom but it was in really bad shape.

BTW, on all my starcrafts so far, the only place I've seen factory ZC under the paint is below the waterline???