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How do you remove rust from steel? - jewlers question from Guild's inbox

Posted: Wed Dec 16, 2015 6:20 am
by Darryl Ponder
From the Guild's email inbox:

"I am a jeweler, using mild steel in jewelry fabrication. I use solder and incorporate karat golds in my work. I'm interested in learning how to remove the rust and "crud" from the steel before applying a final patina."

What method's would you recommend for rust removal from small pieces? Post them here.

I suggested three methods: vinegar solution, molasses solution and electrolysis



Edit added after Martin replied: The artist that made the query is Nina Mann. Here is her website: She has some very interesting jewelry that is a mix of steel and gold.

Re: How do you remove rust from steel? - jewlers question from Guild's inbox

Posted: Fri Dec 18, 2015 12:44 pm
by Martin Pansch
There really isn't enough information in the jeweler's question (i.e. there is degrees of "crud" and rust that require different approaches, is he making 10 pieces or thousands, what kind of finish is he looking for, etc) to know what is the right one for the job so I am just going to list off a way and a brief discussion. I won't go into detail on each as that would be many pages.

Chemical removal: You can use a mild acidic solution like vinegar, molasses, pool chemicals (commonly labeled "pH Minus" in the store) to soften up and remove the scale. Adding heat to the reaction, like with a garage sale crock pot, speeds it up (stay awake for chemistry class kids). Often you'll need to scrub the last little bit of scale off with a green scotch pad. When you have your acid dialed this work really well and you can have as many pieces in as you have volume in your crock pot. It is mostly a fire and forget method in that you can be working on other things while the acid is doing its thing. You'll probably also want to neutralize the acid once you take it out or the acid will keep working on the piece while it is sitting dry on your bench.

Electrolysis: Basically mix up a electrolyte solution (I use washing soda which is NOT that same thing as powdered detergent). Use a battery charger or similar and attach the negative to the item to be derusted and the positive to a sacrificial anode. Submerge in the solution and plug in on a low amp setting. This can work well but the rust is best pulled off from the side facing your anode so to get an all over effect you need to make an anode "cage" to expose all sides of the item. Hooking up more than one item at a time to clean takes a little rigging too. If you are going to do this look up detailed instructions on the internet as there is all sorts of hazards to this (i.e. water and electricity, using the wrong material for an anode and making hazardous solution, etc). Like the chemical method it is also fire and forget.

Wire wheel: If you have a simple piece giving it a quick lick with a wire wheel might be enough. The size of the wheel and wires will need to be gauged to your item, my knotted wire wheel on my angle grinder and my little wheel on my Dremel both have their optimal uses. If you have something with complex bends, curves, etc not only does it make it tougher to get clean with the wire wheel but you have an increased chance of the wires "grabbing" it and throwing the piece at high velocity across the shop. Also, while a quick solution for a couple pieces if you are doing thousands it would get really time consuming.

Sand blasting: This is a pretty common prep method in industry. The blast media can range from sand, glass beads, nut shells, etc. They all have a different level of "bite" into the steel and scale and will leave a different surface finish. Shapes that would present a problem with a wire wheel are okay here though you can still get a tight corner where you won't get the surface suitably prepped. This process takes having a sand blasting cabinet and a SERIOUS air compressor which can be a big investment. No real poor man's alternative that I have found I am afraid.

Tumbling/vibrating: Another industrial practice. This one is good if you are doing a lot of small pieces. You put the pieces in the tumbler/vibrator with some sort of tumbling media. Think of the tumbling media like all the different choices for the sand blasting but bigger. You want to find the right combination of sharpness, hardness, etc to remove the scale, rust, burrs, etc and leave the desired finish on the piece without over working it. You also have to figure the right ratio of parts to media, spin time, whether to include some sort of oil or not, etc. A lot of experimenting to find the right combo but when you do you are set to make those pieces ad nausem and will never have to deal with the prepping them again. Smiths doing bigger things have been known to retrofit a cement mixer into a tumbler though I hear the noise from these set ups can make almost everything else in the shop seem quite. If I was doing small batched of jewelry and was looking to use this method I might look into the vibratory polishers that some home reloaders use to polish their brass.

Torch: For removing forge scale (hey, it's a type of rust) you can turn your oxy/acetylene torch on it. The scale heats up faster than the metal underneath and pops off. I will say though I have never got a completely clean surface this way and sometimes have even melted the scale and scattered it into little spheres that adhered themselves to other parts of my piece. Probably operator error.

Then there is all sorts of manual labor methods you could use: sand paper, files (not your good ones), scraper, etc.

I am sure I missed something. Anyone else?

Re: How do you remove rust from steel? - jewlers question from Guild's inbox

Posted: Sat Dec 19, 2015 12:49 pm
by Martin Pansch
I got this reply from Bob Patrick in an email. A cautionary tail of using either electrolysis or chemical processes if your piece is mixed metal:
"Using electrolysis or chemicals to remove rust from mixed metal jewelry can be very bad. I had 50 pieces of work that were copper brazed I just sent out 2 days ago. I had decided to pickle them in muriatic acid to remove the borax flux I used. Imagine my surprise and lack of delight when I found them all copper plated. I tumbled them with sand to remove the thin copper plating, but when you have more than one metal together in a chemical solution you typically end up with one of the metals dissolving the acid, base, or salt solution and the other being plated by the first metal. That is why we use copper plated ground rods and have a sacrificial anode in hot water heaters. The iron could end up getting plated and the other metal dissolving with electrolysis.

Anyway, that is my experience. I did set up plating entire pieces of steel furniture for a company I worked for nearly 30 years ago. We used a solution of copper sulfate and sulfuric acid mixed with water, mechanically cleaned the metal to shiny and put it in the tank and it almost instantly plated without electricity. I got a book from Lindsay Publications on plating to set it up.

Thanks for letting us benefit from your experience Bob!