sublimate

I posted this in OT but also thought I'd try here:

I have some wheels for my928 that I want to remove the plating from. I'm using a brass rod for the anode, battery acid for the electrolyte, and a battery charger for the power source.

I tried a small test piece (the lug nut cover) and it deplated pretty fast (~5 min) and got pretty hot. I'm worried when I do a whole wheel even more current will flow and it'll overload my charger. Also I'm worried it might not be good for the Aluminum wheel to deplate that fast.

Seems like there are 2 options to slow the deelectroplating process (but please correct me if I'm wrong): 1. use a smaller anode, or 2. dilute the elctrolyte. I'd like to do the 2nd option if that'll work - that way I won't have to buy a lot more acid to cover a whole wheel. But how dilute will still conduct enough juice to work? Currently it's 33.5% Sulfuric acid. Can I cut it in half? Or even more dilute?

Anyone know or know where I can find out?

borland

Let's say you do electro-etch your plated wheels.... How do you plan to dispose of the metal ladened waste chemicals in an environmentally friendly way? Some things are best left to the professionals.

Around here, because of the environmental restrictions, there are few plating shops in the county. Several plating shops here are just store fronts, shipping out customer's work to a limited number of plating plants in Los Angeles. They mostly cater to Chopper and Low Rider hobbiests.

borland

cobalt

How hot is it getting? You want to be very careful with aluminum. If you exceed 500 degrees for more than 30 min you will destroy the temper and the wheel can break apart at speed. Keep a close eye on it. Good Luck.

TRUESCOTSMAN

Not sure why you would want to strip the shine from your wheels, but anyhow. As far as i have done this sort of thing in the past to alluminium alloys, it is normally a caustic bath to etch back the metal no electrodes or power supply needed, followed by a cold water bath to reseal the bared surface. Dont know what sort of finnish you are expecting, but this will give a dull grey/black look to your alloy.......Jim

CWO4Mann

Cut your electrolyte to 5% and work up in 2.5% steps. Use an immersion thermometer to observe the temperature rise of the actual electrolyte. Keep the immersed temperature lower than 150 degrees at all times; once you get towards 150 the heat rise curve is very steep and you can go from 150 to boiling in seconds. You don't want to be around boiling electrolyte or vapor.

Use a laser spot thermometer to watch the surface temperature. If you have one, use a battery charger with a variable output. If not you will just have to keep your eyes on it. When it comes time to dispose of the hazardous waste, pour the liquid into a container filled with diatomatious earth or hazmat clean up absorbant rated for acids. Then contact your local refuse center and tell them you have a quantity of electrolyte laden with cromium salts which is embedded in an absorbant. They will tell you where to bring it for proper disposal.

Do not under any circumstances breathe the vapors; if you value your life don't breathe the vapors. Wear impermeable rubber gloves and an apron rated for high acid concentrations along with a HEPA/OSHA Rated cartridge style mask and a lexan face shield. Ordinary garden or kitchen gloves will not protect you. Plating and deplating is serious business.

We had to get rid of the school plating shop because of the cost of environmental protective measures and still it cost the school district about $10,000 for the hazmat people to certify the area "clean". And this is in a state where the local battery plant used to grind up old batteries and use the fragments to line road beds.

Hope this helps, your mileage may vary, and I can't believe you are doing this at home. Hey Kids! Look! Daddy's on Fire!

Edit added: Dude! this is no joke and I am not being hysterical. Remember I'm the guy that used to jump out of airplanes for a living?

sublimate

Thanks for the tips guys. I tried to find a local place to do it but one wouldn't touch it because it's gold and the other said he'd do it but only just before he changed out his bath. He said he'd call me but when I hadn't heard from him in a while I called and he said "Sorry, I've already changed it out. I'll call you the next time." Not holding my breath.

As for the leftovers - yes, I plan to dispose of it properly. But I think you guys are being a little alarmist. These aren't exactly hazardous chemicals. Sulfuric acid is produced in larger amounts than any other chemical besides water. It is used in many drain cleaners (ie, is poured down many a drain) and fertilizer (ie it is spread on plants). Millions of tons are pumped into the atmosphere every day by power plants (where it does cause probs due to acidity - "acid rain"). It is after all just sulfur (think rotten eggs) and hydrogen and oxygen (think water). And gold is pretty benign too (as those of us with fillings in our teeth can attest). But I do apreciate everyones concerns.

But back to my wheels. I attached a pic showing my test piece and what it looked like before. Obviously the original plating the PO did had some problem because it is coroding all over. Plus it's gold and looks cheesy as hell. Sandblasting seemed to have little effect on taking off the plating (it only helped take it off where it was already flaking off). My powdercoater said he could blast off all the flaking areas and then powercoat. but he couldn't guarantee it wouldn't continue to corrode and bubble thru the paint. So I think the plating has to come off. Any other ideas?

TRUESCOTSMAN

If it is real gold, then you need to get hold of some potassium iodide crystals.
mix with water, and either apply by brushing or mix up plenty and dip. Not very nice stuff though. Dont get it on your hands, it takes about a week to wear off. Mixture depends on how quickly you want it to work and how thick the plating is. Ten years ago i could have told you the mix/time/ thickness, but it has been a while.

G Man

You are right that the chemicals you intend to use are not that dangerous. WHEN THEY ARE SEPERATE. Once combined you can have real trouble.I'm no chemist, but I know it is not advisable to mix certian chemicals. Perhaps you will not mix them, but the combination of the chemical and the material it etches off of the wheel could be toxic. What do you get if you mix household bleach and household ammonia? CHLORINE GAS! If it were me I would let a shop take on this project, even if you have to ship your items cross country. Like Dave said. Please be careful. Hope it turns out the way you want it to.

jon928se

I am no chemist but I am pretty sure that I wouldn't use H2SO4 as an electrolyte to strip plating off aluminium wheels. I only need to to look at the effects of Salt (NaCl) without the benefit of an impressed current on aluminium wheel nuts.

Having said that why brass as an anode ? I have used carbon fibre as an anode in a very very weak salt solution to remove chloride ions from steel in an 80 year old warship with success.

Good luck if it works but I would be wary.

Jon in NZ
amatuer chemist.

sublimate

I've looked at etching solutions and they all seem to be more hazardous than what I'm using now. Plus from what I've read they'll etch the Aluminum as fast if not faster than the gold. http://www.transene.com/etch_compatibility.html

cobalt

I agree. I would be careful and attempt to figure how much matrial is being removed. I would start with a test block and measure it as accurately as you can. Run the piece through your process and measure again to see how much material was removed for the time in the bath.

TRUESCOTSMAN

Gold is a noble metal (does not corrode). the corrosion you are getting is from the alloy underneath, and is coming through where the gold plating has not been very good. If this guy can clean up the corroded areas then powder coat to seal the alloy, then by rites it should not come back.

Alternatively, If the gold flash that has been put on by the previous owner is that thin, then etching the gold back using a brushed on potassium iodide solution and then blasting and powder coating would cover up any blemishes.

heinrich

BOOM!!