Hey guys. I just got a few 97 carbs, and two of them have been chromed. I want to remove the chrome without damaging the aluminum. I tried a little bead blasting, but it's not doing much of anything to the chrome, and I don't really want to hit it with anything more abrasive. I know it's possible to use electrolysis to remove the chrome the same way that it's put on, but before I go ahead with it I just want to make sure that I have the process right so I don't end up blowing myself up. This is how I've been told to do it: Mix 1 cup of muriatic acid with 3 gallons of water in a plastic bucket. Run a couple of copper wires from the negative side of a battery into the bucket, then connect the positive to the carb and dunk it in for a few minutes. This, I'm told should remove all the chrome and leave the aluminum clean. If any of you guys have done this before, or have a better way, or have tried this and know it's bullshit, I'd really appreciate the info. Thanks guys. -Dan
I didn't remove it, just dulled it rubbing with WD40 and scotchbrite. Still same color but not shinny.
Any home brewed chemical ways to come up with strong enough to take off chrome will destroy the aluminum. Just take it to a plater to have it taken off right.
DO NOT USE MURIATIC ACID ON ALUMINUM. It will eat the chrome, leave the nickel and copper (if any), and destroy the aluminum base metal. We normally use a sulfuric solution with electrolysis for stripping aluminum. And BTW, removing the chrome is very easy and can even be done with some household cleaners. 99% of the plating's thickness is the nickel which is the harder part to strip.
You may be able to find someone to trade you your chrome 97's for some not chrome ones. Just a thought...
Thank you. That's good to know. What kind of household cleaners would you suggest? I have thought about this, but the chrome is kind of old and crappy.
First off, 97 carbs are made of zinc, commonly called pot metal, not aluminum. The bases are cast iron. Use sulfuric acid, the same as in batteries. If you can get full strength technical grade acid, mix with equal part water. If you only come up with battery acid I believe it is about 1 to 3 already, use as is. The weaker acid solution will etch the parts more. Use a piece of stainless with area at least as large as part you are stripping and connect to -. Carb to +. Now the bad part. Any acid solution will eat zinc, you hear the stories about the chrome shop that ate parts. It happens. The internal parts & recesses in the carb are not plated as thick as the external areas, and while the solution is dissolving the chrome, nickel & copper it is also eating the bare zinc in the internal passages. It may render the carb worthless, you can plug all internals with silicon. Some high end plating shops are starting to use expensive chemicals to strip plated parts & reportedly not damage the base metal, but may not take all the copper off. Will probably be expensive. Have fun & don't splash the stuff.
It is a zinc-aluminum alloy, not pure zinc. Personally, I would check the part out before putting it into any sort of stripper. Sulfuric would still be my primary method of stripping nickel from pot-metal. We do it everyday. The only difference here is that the carbs have some intricate areas with some tight tolerances that may need to be plugged for safety's sake, especially because of the much thinner plating on the inner surfaces, as stated already. When parts get destroyed chemically it is either the parts are put into the wrong acid (aluminum or zinc alloy into muriatic,) or they are put into the correct acid for way too long.
So, it being a Zinc-aluminum alloy makes it safer to use with the acid? If so, would you use the same method that I had outlined before, but just substitute the muriatic for the sulfuric acid? And as far as plugging up the intricate areas are concerned would you suggest using silicone, as said before?
I can't speak for Josh, but I'm not a metallurgist, can't say that I've ever seen any claim on what some of the alloy of what we commonly call pot metal is. The newer stuff is called Zamac & is supposed to be about 99% pure zinc. I know the older stuff is inconsistent. Some of it is softer, some is brittle. Some will weld, some will fiss, sputter and never puddle well enough to weld successfully. Some may have some lead, aluminum, magnesium (I think that's the stuff that sputters), copper or anything else that they sweep off the floor. Sulfuric wont eat aluminum, but most aluminums are alloys too & the acid may eat the alloying metals & leave pits. Most alloys only have a small percent of the alloying metal to change the characteristics of the base metal, usually 5% or less. I'll go out on a limb & say the carbs are probably 95 % zinc & you still have to mask off any areas you don't want the acid to dissolve. Use extreme care with your personal safety, wear rubber gloves & safety glasses. Don't let the deq catch you dumping the used acid down the drain. They would throw me in jail for that, use your best judgment!!
After much consideration, I decided that screwing around with any sort of acid to remove chrome is much too unsafe for use without the proper facility. So, I cranked back up the bead blaster, grabbed some 80 grit and the die grinder, and after a few hours of good ole' fashioned American determination, and a lot of elbow grease I almost have one the carbs completely stripped.
Zamac is simply a pot metal with a somewhat specific standard of ingredients. Pot metal of yesterday, which I deal with replating all the time, is still zinc-based, but the rest of the ingredients can be many different metals (lead, copper, tin etc.) When plating unknown composition pot metal or zamac parts, I treat them all like pot metal; Using Sulfuric for stripping, and a cyanide copper strike for first plating. And I am no metallurgist by any means; I just learn what I need to know to be able to do what I do. The safest way to strip the carbs is to mechanically (abrasives) remove the plating as you have already started doing. That way the insides of the carbs remain untouched. It takes longer, but leaves no questions.
@Dicimato. The best ,safest and most efficient way to strip the plating off your carbs .Is take it to a reputable plater. Sulfuric reverse strip is the best method. The sulfuric strip I use is mixed with glycerine , which aids as a buffer , to minimize etching of the base metal ,in your case is zinc die cast, and cast iron.When done properly should not attack the internals. The more water that is present in this strip ,the more aggressive the strip, so if done at home caution to the % of water to acid.
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