removing rust

[J Burns]

Stormin Mormon soaked rusty pliers in HCl. Rbowman recommended phosphoric acid, sold to etch concrete. That reminded me of naval jelly. I knew it contained phosphoric acid. It also contains a gel and rubbing alcohol. I wonder what the rubbing alcohol does.

I've had some success with vinegar and with vinegar and salt. Now I've read the proper way to use vinegar and salt. Use an inert container such as plastic or glass, big enough for the rusty item. Pour in enough vinegar to cover the item. Stir in an excess of salt. Put an inert spacer on the bottom to keep the steel from contacting the salt. Let the item soak, completely submerged.

Vinegar works, but this mixture also contains HCl. The acetate apparently keeps the HCl from eating the steel. You can pull the item out to inspect and brush. When it's ready, immediately wash and oil.

Phosphoric acid is sold for converting rust (not removing it). I don't know the concentration of the etching stuff, but Ospho is 75%. (Naval jelly is 25-30%.) You brush or spray Ospho on and let it dry. If the surface is badly pitted, you may repeat. If you brush away any white powder, you have a good base to paint.

Ospho says their product can be used if you want to repaint spots where rust is coming through a painted surface, but you should test to see if Ospho damages your paint.

I'm looking forward to trying the proper method of using vinegar and salt.

[KLayton888]

I use Evapo-Rust:

Works great and can be reused dozens of times. Available on the shelves at O-Reilly Auto Parts and Harbor Freight.

[nestork]

Both hydrochloric acid and nitric acid will dissolve rust, and IMHO, those are the only two ways to go.

Phosphoric acid simply converts the rust into a relatively soft black compound called ferric phosphate.

Your idea of adding salt to vinegar is going to create an electrolyte so that if the steel is galvanized, the zinc coating will be eaten away if the underlying steel is also exposed. I really don't see how a salt/vinegar combination is going to remove rust any better than hydrochloric acid.

Hydrochloric acid attacks rust much more aggressively than it does bare steel, and it's worked well for me. When my sister's snowblower wheel was rusted onto the drive shaft, I was able to free it by applying hydrochloric acid with an eye dropper to the joint between the wheel's hub and the shaft. Capillary pressure drew the acid into the joint between them, dissolved the rust, and the wheel came free. The drive shaft appeared to be completely unaffected by the acid.

[J Burns]

Wow! They don't say what's in it except a that it's a chelator/detergent. It's not hazardous, but you shouldn't drink it or get it on your eyes. Soak to remove rust, rinse, and dip for rust protection. A modern marvel!

[J Burns]

It seems to make a better base for primer than bare metal. I used my license plate 100,000 miles over several years with no garage and no paint failure or rust.

I hadn't thought of dunking something with a zinc plating. Isn't an HCl solution an electrolyte? Vinegar is 1/10 normal acetic acid with a pH of 3. Salt has a pH of 7. The mixture sounds safer for people and materials than a 1/10 normal solution of HCl, with a pH of 1.

Marv Klotz described it. He has a machine shop. He has tried HCl but says he won't have it in his shop now. He says if you keep the item submerged, the vinegar/salt solution won't attack the base metal.

[Stormin Mormon]

When my sister's snowblower wheel

Wish I'd known. A couple years ago, a friend asked me to try and get the blower impeller off his snow blower. He ended up using torch, grinder, etc. Maybe some HCL would have done it.

. Christopher A. Young Learn about Jesus

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[dadiOH]

That's a matter of degree. Try vinegar/salt with some old copper pennies first, then steel. The steel will wind up copper plated because of the copper that was dissolved.

[RobertMacy]

the alcohol dissolves any water, as in dehydrates, dries. You can use it to rinse a wet item and speed the drying time.

[J Burns]

How long should I soak the penny? I guess the bath would be opaque with dissolved copper.

[J Burns]

Naval jelly must contain water to make the acid work, but I think you're onto something.

I sometimes use rubbing alcohol to get water out of my ears or off a circuit board. It lowers the surface tension so the water flows away. By lowering the surface tension of naval jelly, rubbing alcohol would help it penetrate rust. Drying agent, wetting agent... same thing!

So if I were going to use phosphoric acid on deep rust, it might help to mix in some rubbing alcohol!

[dadiOH]

Long enough for them to get shiny. The dissolved copper will be in ionic form, can't see it.

[J Burns]

Aren't copper ions blue?

This afternoon, I shined up 2 pennies, 2 dimes, and a quarter, all in an ounce or so of salty vinegar. The appearance of the vinegar stayed the same. I didn't see any copper from the edges of the dimes and quarter, deposited on the faces.

[dadiOH]

Steel. Use steel.

[Ashton Crusher]

My experience with it was that it's almost worthless.

[J Burns]

You want me to use a 1943 penny?

[nestork]

No, copper sulfate is blue. The acid rain that falls on the copper roofs of cathedrals in Europe causes the copper roof to react with the sulfur in the rain to produce copper sulfate, and hence the blue-ish green-ish roofs. Sulphur is a common impurity in coal, and when coal is burned the sulphur in the smoke reacts with water vapour in the air to form sulfuric acid, or "acid rain".

If you dissolve copper sulfate in water, so that you have copper ions and sulfate ions, I really don't know what colour that solution would be, but my guess would be that it would be a light blue. That's because in a solution like that, most of the copper sulfate will dissociate into ions, but there is always going to be some reassociation in the water to form copper sulfate from the abundance of copper and sulfate ions present. That is, there is going to be an equilibrium formed where ions combine to form copper sulfate in the water and then disassociate to form ions again. What little copper sulfate exists in the water will cause a blue-ish tint.

[J Burns]

I looked for a steel item that I was sure wasn't plated. I tried a rusty screw with a penny. I got bubbles, a black, water-soluble deposit on the penny, and copper on the screw.

[J Burns]

Copper sulfate is a white powder. Magnesium sulfate is a white powder.

Water with dissolved magnesium sulfate is clear. Water with dissolved copper sulfate is blue. The blue must be the copper ions.

[dadiOH]

Right. The acid - even though weak - dissolved some copper. Those copper ions are positive. The acid also dissolved some iron; those ions are also positive leaving the screw negative. The copper ions are more strongly attracted to the screw than are the iron ions. The bubbles were hydrogen gas. The black would be an iron salt.

[Percival P. Cassidy]

Anhydrous coppers sulfate may well be a white powder, but the only form in which I've ever seen copper sulfate (other than a solution of it) is as the blue crystals that contain a significant amount of water.

Perce