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More on Rust Busters
an excerpt from the ZCCW Newsletter
Compiled by: James Lux
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You may recall a previous article in The NewZletter on Eastwood's anti-rust products. Three recent posts in the 240 group with further comment on these products--from Pete Paraska and Carl Beck--are worth repeating here.
Pete Paraska wrote:
Josh Pryor wrote: I have a 240z which is stripped to bare metal, what do you all think I should use as a base primer to ensure many years of rust free driving? Walter Meares replied: I used an epoxy primer (PPG DP40). Before priming I used a metal treatment to remove any flash rust and put a light galvanizing coating on the metal. I don't remember whose product that was, but there are several out there.
(I got kind of preachy here. This subject is real close to my heart :) I used Eastwood company's "Oxisolv." It is a phosphoric acid solution that contains some Zinc. It removes (not converts) rust and leaves a light Zinc-Phosphate coating on the steel to prevent flash rusting. There are other products, I'm sure, but this stuff does work. It takes time and temperature to do it's work, though, and you need to clean heavy rust off. By temperature, remember that the rust removal and zinc-phosphate treating processes are chemical reactions that have rates of reaction that go up with temperature. I found that if I heated the metal with a torch, or put a heater under the car (it was on a rotisserie), the reaction went much faster, and it was easier to get a more complete (darker) zinc phosphate treatment on the metal. This also speeds up rust removal. If you heat the steel too much it evaporates away quickly or boils off if you really over-do it. That high school Chemistry class was good for something, huh!? ... But for treating a car that's been stripped of paint, and maybe sand blasted, Oxysolv works great. I did just that to my shell after it was (gingerly) sand blasted. It stayed rust free in a garage in 20-60 degree F, sometimes humid weather for 6 months while I worked on replacing rusted-and-gone steel areas.
Whatever you do don't even attempt to use the rust "converters." They only convert the top layer of rust and it continues to rust underneath. If you can't get to an area (I had a few of those), and you suspect surface rust (it's there, Datsun did a horrible job of treating non-exposed areas), you might get away with something like Eastwood's Corroless. That's what I tried. Talk to me in five years and I'll tell you if it rusted through the back edge of my roof. What I'm saying here is REMOVE the rust, don't try to CONVERT it.
I agree with the epoxy primer. Zinc Chromate would also be good, but it's not as tough as the Epoxy, and may not adhere as well. All the resto-shops I talk to say the Epoxy is the way to go. Of course, I bet the EPA would rather you not use Zinc Chromate, since Chromium is one on their nasty list.
DISCLAIMER. I don't work for Eastwood or anything, I just spend a lot of my resto money with them. There are probably other companies that sell similar stuff. Their WWW page is at http://www.eastwoodco.com/.
Stephan Youschak then wrote a reply to Pete's post, to which he replied as follows:
Stephan Youschak wrote: "RE: Pete Paraska's recent post on Eastwood's Oxisolv.... I found an alternative to this product that likely is locally available to almost all of you. It's called "Phosphoric Acid Cleaner", by AquaMix. The Aquamix liquid is available in quarts and gallon jugs, and it is cheap. Probably less than the premium Hazardous Shipping charges alone that I think may apply to a mail order quart of Oxisolv.... thus I can only guess how much more it would cost to ship Oxisolv. Perhaps Pete can shed some light on this."
Actually, Oxisolv doesn't have a Hazardous Shipping Charge, as I was surprised to find out when I just looked in the catalog. It's $10 for 16oz., $25 for a gallon, and $119 for 5 gallons. (You can tell which of Eastwood's products are hazardous shipping ones by looking for a Z at the end of the part no., which none of the Oxisolv part numbers have.
I like the idea of using the cheap Aquamix stuff to eat away the rust, then using Oxisolv to put on the zinc phosphate coating it provides after the rust is gone.
Bill Reagan wrote about using a rust eater product that didn't coat the steel with any kind of zinc coating, and said it would flash rust quickly, so you should immediately paint the BARE steel with zinc chromate primer (Dupont's Variprime WITH zinc chromate). I prefer using Oxisolv, not rushing, and using self etching epoxy primer. To each his own.
My point is if the product does not provide some sort of rust preventative, like a zinc phosphate coating, you need to be very quick to paint the bare steel. So if you use Aquamix, be sure to either hit it with primer or Oxisolv, etc. very soon afterwards.
One more thing. You must be careful not to use too strong an acid. If it's too strong, you start to get hydrogen embrittlement of the steel, which means that the steel gets brittle and will crack up easily. I found this out using straight Muriatic acid (HCL) for swimming pool use on steel. Plus, the stuff kept corroding the steel and was hard to neutralize. Stick with the weaker phosphoric acids. I'm not sure how strong Aquamix is, relative to Oxisolv. .... I'd guess Oxisolv is pretty weak, since it doesn't have hazardous shipping charges, and I can get it on my hand without it burning much at all. This is not a knock on Oxisolv, I may yet order some if it truly zinc-coats the parts.
It really does protect it from flash rust. I've left steel treated with Oxisolv in warm, humid environments for months and saw no rusting. But you shouldn't wait that long, I don't think.
Carl Beck also replied to Josh Pryor, beginning by quoting Josh's post: Josh on Monday, asked: ñI have a 240Z which is stripped to bare metal, what do you all think I should use as a base primer to ensure many years of rust free driving?î
That depends on a number of things that you didn't tell us.
If it was stripped to bare metal by dipping the entire body shell into a chemical stripping tank....then it must be dipped in a rust proofing primer.
These are usually fish oil based primers.
This is the only way to assure that the body seam sealer which was removed by stripping and all the cracks and crevices that you can't reach, are sealed again with something. So the only thing you can do is dip it in whatever primer/rust preventive the stripping shop has.
Above that - if you are going to spray the primer on clean metal, then you need to use a self etching epoxy primer. Most major manufacturers supply this as part of their complete paint "systems." But I hasten to add, that this is intended to go over CLEAN bare metal. Also, any body filler MUST be applied over the top of this sealer to assure that the body filler doesn't draw moisture through the metal. (Moisture drawn through the metal, is mainly what causes the body fillers to bubble up a year or so after they has been applied).
IMHO - Best results are achieved when you visit your local automotive paint store, and select a specific brand of paint, then use that vendors products and follow their recommendations. (Don't mix vendors products unless you know what you are doing from years of experience and lots of paint jobs behind you).Ê
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