Muratic acid

[blt2krl]

Is it okay to use muratic acid to clean up my steering knuckles? I want to put a new coat of paint on but would like to take the little layer of rust off.

[wagdriver]

I don't think you want to use muratic acid on any of those components. You would do just as well to wire brush them off as best yon can and use a rust converter on them, then prime them with a good rusty metal primer and paint as you like.

[JINGA]

Concur. The muriatic is a no-go in my book.

Get the loose rust off (like suggested above). The rust converters often want a little bit of rust to be present in order to convert. I buy straight phosphoric acid when I can get it. Sometimes I spot it in the hardware stores, but usually I go to an autopaint supplier. I follow the directions on the bottle. Usually I have to dilute the stuff, then paint on and let it sit. I normaly wait until the next day to paint.

HTH, Jeff

[blt2krl]

Phosphoric acid works better? Do you guys think that Muratic acid (HCL acid) is to strong?

[blt2krl]

I just thought of a better idea. I can just use a sand blaster and blast that rust layer off. No rust converter and no hazardous chemicals.

[ClarkGriswald]

Ive used muriatic for years on stuff just like that.. only thing is there is a trick to it..

If you rinse it off with water, the second dry air hits it .. BANG its rusty..
It will even rust as you hose the acid off with water..

I use it to etch real bad rust off stuff. and then I hose it off.. and while it is still wet.. I drench it in WD-40 (water displacer).

This will minimize the rust somewhat.. ( I still use rust converter and all that too)..

But those rust converters are tricky .. they need rust to work, but there is no way they will "soak in" to heavy rust.. your only dealing with the surface so the reaction keeps happening underneath..

I only use rust converter as a Pre-primer. To get that last bit of rust that is in the pours of the metal..

WATCH YOUR BUTT with muriatic acid.. If you have ever had to go down into a swimming pool with a respirator and gloves/boots/ect.. and scrub the marsite down you KNOW how bad it is.

Dont breath it..

[Stuka]

Cg is righton with his post.. f you have ever had a engine acid tanked and you get water on it. it rust instantly.

[JINGA]

When I was doing my undergrad in mechanical engineering I did a project researching different types of anti-corrosion coatings.

A lot of what I read was sales-pitch, but I think there is a certain amount of truth to some of it. In the end (not to simplify this too much) the muriatic acid will eat away the iron oxide (rust) and remain active, rusting some more. Like was posted above, the etched steel will continue to rust.
Phosphoric acid works by binding with the iron oxide. I believe it's a phosphorous ion that displaces the oxygen and binds with the iron ion, but I might have that all mixed up. Anyway, the upshot is that the phosphoric acid will react with rust if it is present (as mentioned above by myself and another poster) but it will not continue to react.

That might not be ecactly right, so don't take it as gospel. The rule of thumb I use on this is: Muriatic acid will eat the rust but will continue to destroy. Phosphoric acid will react with existing rust but is not destructive.

HTH,
Jeff

[solar@clnk.com]

Hi:

I have been removing rust from antique cars for years and agree that phosphoric acid is the VERY BEST solution.

The ultimate phosphoric product is "Chemprime Rust Inhibitor". It is a green solution, available everywhere in gallons for about $12 and it is really safe, but very effective. The good thing is, you can spray it inside doors and behind fender panels and just let it dry AND LEAVE IT !!

I always spray it on sand-blasted metal too as it will not let rust start.

You can prime over it, paint over it, undercoat over it, or just leave it as is.

This product carries a good Mil Spec.

I use a windex spray bottle to apply it.

Great Stuff! smile.gif

[blt2krl]

Hey thanks solar@clnk.com, I think I might try that. I plan on sand blasting the parts first. Can I get that Chem Prime Rust inhibitor a the local auto parts store?

[solar@clnk.com]

Hi Ya:

I think you will find it more quickly in any good hardware store. We have 3 hardware stores in my little town and all 3 carry Chemprime.

The really-big users of the stuff are farmers and ranchers with stock trailers.

The manufacturer of Chemprime is;
Al-Con Chemical Company
New Orleans

smile.gif

[Veepster]

hhhmmmm......Clark, now we know why you are the way you are!!.... :D

[JINGA]

I just read about a product that uses phosphoric acid and zinc. This sounds like a great combination. The phosphoric acid will convert the rust and the zinc is left behind as a preferential (sacrificial) coating.

Next time I'm in the market for one of these products I'm going to look for the Phosphoric acid and zinc combo.

Jeff