What is correct acid to stop flash rust?

I have some parts I blasted a while back and some of them have some flash rust on them. I wanted to remove it before painting. Does anyone know what to use on the metal to get rid of and avoid any rust. Is it muriatic acid? Does it need to be neutralized after treating? Thanks

 

I use PPG's metalprep, which is diluted phosphoric acid. The parts should then be neutralized with water, force dried (if necessary) and primed. I prefer epoxy primer over everything, even before body filler.

Devon

 

body shop supply stores sell "Ospho", which is phosphoric acid for bare metal prep. You coat the panel and let sit for 12-24 hours to cure, which is supposed to prevent future rust.

-Josh

 

Phosphoric acid. OK thanks. I guess I should quit drinking coca cola as that is what is in that. Cannot be good for the bones I guess but it wakes me up.ou:

 

Or hit Home Depot and get some Behrs 'Concrete etch and stain remover'. It's phosphoric acid based. I have to thank George at www.buickperformance.com for that tip.

It's relatively inexpensive, so it's great for shop use. I wouldn't recommend it for good body panels, without thorough testing.

Picklex-20 is a nice product, but it's $130 a gallon.

 

I have some of the Behers but isn't that muriatic acid?

 

ppg part # Dx579 available in qts and gallons
Basf # 801 available in qts
Dupont # 5717S available in qts and gallons
all phosphoric acid base and need to be neutralized with water....they leave a phosphoric coating that allows primer to bond to the acid etch....do not use an Acid Based Self Ecth Primer on acid treated panels....only use epoxy or 2k based primers

 

muriatic acid is a weaker version of hydrocloric acid...it has no corrosion protection....in fact it make metal even more rust prone unless you coat the bare metal right after cleaning with an epoxy primer.....have seen muriatic treated panels flash rust in about an hour in humid conditions.....where as the phosphoric acid based preps actually deliver a phosphorous coating onto to the metal to prevent rust

 

Exactly what I was going to say! I used to use muriatic acid to ENCOURAGE rust back in art school...

 

Phosphoric.
More info here on the Behr website:
http://www.behr.com/behrx/act/view/...=8&catName=Cleaners+and+Conditioners&catId=14

 

Thnaks for the info. I checked my Beher label and you guys are right it is Phosphoric. So should I rub with some kind of cleaner after treating with acid?

 

Nope, just clean water to remove & neutralize the acid. The metal will want to start rusting again right away, thus my comment about drying with compressed air and/or heat and then an immediate epoxy prime.

Devon

 

That sounds like the proper procedure, Devon. But I can't bring myself to rinse bare metal with water! If it turns blue, you're okay....but if it flash rusts, I freak out, and do it all over again. (been there) You should be okay with the quick blow-dry, tho. Most metal conditioners do require a rinse. Some contain alcohol, and do not require rinsing...
I'd suggest reading the label before you purchase the product.

What I like about Picklex is that you apply it, keep it wet for a min or two, then wipe dry and paint. No rinse required. If you do let it dry on the surface, it will leave a film....probably not a good idea...wet it and scrub again, and wipe dry.
Maybe you could get away with the same procedure with other phosphoric-based treatments?
My procedure...spray it on, then scrub the area with a scotch-brite pad and keep it wet for 1-2 min, then wipe off. Before painting, I go over it with a dry scotch-brite and compressed air . That'll remove any fuzz and film build-up. Then prep-sol, and prime. I also like epoxy primers. Good stuff!:TU:

 

Thanks for this good info. I am going to thry the beher. I have a phobia about using water on bare metal as well.

 

With phosphoric acid.....Behr and regular phosphoric acid are both available at Home Depot in the paint section.....you simply apply it with a brush and let it sit overnight. Wipe/brush off any white chalk residue and wipe down with lacquer thinner or acetone. I do this all the time and it works great. Never had a problem in 20+ years.

 

George, do you use it full strength?

 

you really should look at the MSDS sheets for the product......from a paint supplier perspective...the behr products are 30-60 parts acid...the automotive paint companies are alot less..sometimes more is not better as the phosphoric acid is also an adhesion promoter for the primer to stick to....which is why the paint companies do not recommend using an acid etch primer on top of their metal cleaners..... just thought I should put it out there.... you should really stick with paint MFG's recommendations

 

Yes, I use it full strength and it lasts......best test is our 80-100% humidity days here in summer....no rust appears after it is applied.

I switch to the regular phosphoric acid now.....clear jug with green liquid...I believe it is the same price as Behr's version.

 

Thanks, I will try it soon.

 

Advance sell a product called ''the right stuff'' Works great. green liquid. Just follow ist. on the bottle.