Dont Use muriatic acid on metal!!!

I use it on chrome and nickel plated guitar parts when I want to AGE them and make them look 50 years old!

Why would you want to age your Porsche?

rust, I'll show you rust!
 

Muratic acid. I use it all the time on steel to remove mill scale and rust. yes, you don't want to dip your porsche or delicate parts into it and walk away though. I use it on steel that can be throughly cleaned/neutralized following treatment. You just don't put it on then go away for a few days. It is all a matter of timing and keeping an eye on what is happening. I have used it on large deck areas of marine vessels, applied with a sprayer then neutralized with soda. IMHO, all treatments are stopgap with sandblasting being the best. The coatings following the treatments are also critical with the need to block oxygen from contacting the substrate that has been derusted. I did do the floor pan of my Porsche with a needle gun, wire brush, muratic acid applied with a brush, then baking soda and water, followed by phosphoric acid then a 2 part, surface tolerant epoxy. Rust is my constant companion, I maintain barges, tugboats, and cranes/piledrivers in a marine environment. One very nice tool that I have for auto repair is a Snap-On spot blaster. The sandblast media is all contained by a rubber nose piece on the blasting gun and then recirculates into a cloth bag. It works superbly on small areas.http://forums.pelicanparts.com/uploa...1164581232.jpg

That's not proof that MA is not appropriate on steel, or at least not handy. I have to agree with billyboy on the complete removal of the rust and all of its discoloration. Just converting rust to another compound might be fine for your iron gate, but not automotive restoration.

I know because I've been bit on this before. If you consider my late teens and early 20's time spent in the fiberglass industry, followed by 10 years as a painter (houses, cars, factories, all of it), I've been around the coatings industry all my life.

I'm happy when all the steel is silver looking. At that point, all you need is some epoxy primer for excellent protection. On industrial work, other primers work well, too.

POR 15 is an excellent concept, IMO. I use it in cavities where I can't access the metal directly. I shoot it in the cavity and follow that with a long, thin tube on the end of an air nozzle to drive the wet POR 15 all the way to its destination. I follow that with another wax type treatment for some extra insurance. This all after an acid wash, of course.

Interesting points brought up here. I seem to forget that when using muriatic acid to "AGE" metal parts it does take a Looong time.

Subcribing. Excellent thread!

wow! obviously a popular topic, sadly. as a trade auto painter/bodyman I enthusiastically agree with Milt. get the metal silver then epoxy it. I like ppg dp epoxy, it can be mixed to have a shelf life of a week and can be applied almost any way you like. I COAT my parts with this stuff. I mean get it everywhere possible by spray, brush, rag, q-tip, etc. parts without movable pieces I like to dip, swish around, and hang to dry. it dries to a nice satin sheen and is very durable without topcoating. sun will cause it to chalk but doesn't seem to affect it's integrity. all in the name of fighting the dreaded FeO2. Don.

Your absolutely right, HF my mistake. I should know better.

No biggie. I just did not want people to get alarmed over the wrong thing.

Trivia question.... Where can you buy HF over the counter in Oregon?

Surprisingly enough.... there is a producut called "Wink" in the cleaner aisle at my local Fred Meyer. Scary isn't it?

OK, here is my understanding of acid treatments. Actually if you do Yahoo engine search you can find a fair amount of information regarding this topic. As I understand it from my internet research, most acids will dissolve rust. Sulfuric, hydrochloric, muriatic etc., etc. However, these acids do not differentiate between rust (undesirable) and metal (desirable) In other words most acids will dissolve the rust but they keep on going and dissolve the metal. The beauty of phosporic acid is that not only does it dissolve the rust, but it won't dissolve the metal. In addition it will turn the unstable rust (rust never sleeps) into a stable compound which is black in color. Most rust products, if not all of them, incorporate phosphoric acid in their formula.

As far as obtaining a shiney metal surface in the restoration of a car- absolutely no argument there. The 10,0000 dollar question is, how do you do that? I did see one internet thread where the guy produced bright shiney metal with Naval Jelly and steel wool. Looked easy enough so I tried it. Not so easy. Of course there is grinding, but that still leaves small flecks of rust imbedded. So what's the answer? Sand blasting? Though that process has its drawback, the removal and distortion of desirable material.

I have very limited knowledge about this, but I have used the POR-15 metal ready, which contains phosphoric acid.

Well I tried it on my front torsion bar caps. It converted (not removed) the rust to some black stuff. When I took my wire brush to it there was still rust underneath this black coating...

to get a shiny surface on acid-treated parts I've had good luck with a 90 degree die grinder with 3 inch roloc discs (like a little scotch-brite wheel). used with discretion these don't damage the steel. when I must I use a truly archaic method involving increasing fineness's of sandpaper combined with steadily decreasing fingerprints. better yet, chicago pneaumatic makes a little pistol grip orbital sander that uses 2 or 3 inch pads. starting with 80 grit, then 180, then 280 leaves a primer ready metal surface. it's my understanding that the iron phosphate surface left after the acid treatment is inert and stable. due to my extreme laziness I often wind up just hitting some parts with epoxy after the acid bath. I think the key is that the rust is GONE first, I don't trust products like por 15 that "encapsulate" the rust. the rust is still there and it only takes one scratch to allow moisture in and continue the corrosion process under the paint where you can't see it. scatch an acid soaked part and you see bright metal, not more rust. Don.

If you dip your rusty parts in some kind of acid, like muriatic, is it enough to just wash them in water and dry them after?

Subscribed. I'm about to get into a bit of rust removal so this is timely.

I just rinse them off well. I have also dissolved baking soda in the water to neutralize the acid but have not seen any difference. It is important to wash the steel with a good degreaser like Castrol Super Clean, before the acid dip since the acid can't work on an oily surface. The products like corroseal, ospho and navel jelly, and other converters are only OK on very thin rust and the more that can be removed mechanically, first, the better. There is some relatively recent technology with blasting with soda(not soft drink) rather than sand or copper slag. It is supposedly more environmentaly friendly but probably not available to the hobbyist. A bead blast cabinet is a great investment for doing the small and medium size parts. You can use different media depending on the finish desired.:p I feel the same way, even if you can't see it, it is still there working. I have chipped off plenty of really tough epoxy coatings that were raised like pimples with rust growing underneath. The problem is the microscopic rust that is left in the pores of the steel. Of course, on a car that is not going to see saltwater immersion(hopefully), you should be able to halt the spread satisfactorly, with a few of the methods presented here.

Figured I'd bump this to the top for those who have yet to discover electrolysis. I find this method much nicer to deal with than various acids. Personally I ran across the method on a Swedish site by accident and made some trial runs with scrap. It works really well, with little effort and without leaving acid residue.

So far I have used it on my rear calipers, caliper pistons, and camber plates. The pitting left behind is from the rust, not the electrolysis. It doesn't affect healthy steel.

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yup. been there done that. it does work well. some good procedures here...

Rust Removal Using Electrolysis

and some vids that show it...

ww2 relics cleaning with electrolysis. - YouTube

http://www.youtube.com/watch?v=54ADeB6V1rQ

Do you cut the muratic acid at all? I am guessing no as I think it does it's thing once it hits water, or most anything (like your calves when you are putting it in the pool if a little sloppy), but I don't know.

I have used both methods with good success, and usually use them in combination:

- Electrolysis followed by hot water rinse and OSPHO coating to passivate (usually for large parts)

- Weak solution of CLR (calcium, lime, rust remover - mostly HCl acid as the active ingredient) in the ultrasonic cleaner to remove majority of rust on small parts, followed by hot water rinse and a dunk in OSPHO to kill any remaining surface rust.

Hydroflouric acid as popularized on Breaking Bad:

<iframe width="560" height="315" src="//www.youtube.com/embed/hUFbOAIWjJM" frameborder="0" allowfullscreen></iframe>

However, since debunked by the good folks at MythBusters.

Sherwood

Eastwood Rust Converter | Rust Converters | Auto Rust Converter I've used Eastwood's Rust Convertor for years on many cars and motorcycles, it does a great job