Stop or fix discoloration of chrome motorcycle exhaust?

A. Learn to love the blue look because repeatedly abrading a surface with any product will destroy the chrome luster. But, yes, there are many commercial products including Blue Job ⇦ this on eBay or Amazon [affil links] and ⇦ this on eBay or Amazon [affil links] which claim to remove it. We don't offer testimonials or compare products here though (why?)

A. To simulate this process you can use a battery charger ⇦ this on eBay or Amazon [affil links] , a piece of copper tubing, some fiberglass cloth to cover the tubing, and some watered down muriatic acid ⇦ this on eBay or Amazon [affil links] about 2 parts water to 1 part acid. Wrap the fiberglass around the tubing. Hook up the negative clamp to the tubing and the positive to the muffler. Turn on the battery charger to start mode, about 60 amps at 12 volts setting, and then dip the fiberglass into the acid and rub the area to be cleaned. The blue magically disappears. IMPORTANT: wipe off with water and wash right away. Try this on a scrap piece if you can first.

A. Dennis:

I doubt that your pipes are plated a "Gold color"; more than likely it is discoloration of the existing plating from the exhaust heat or a ceramic coating process. Even Stainless Steel will discolor when exposed to temperatures that engine exhausts produce. There are several commercial products out there that might help to clear the discoloration. Check with your local bike shop for their ideas. Hope this helps.

A. Dennis,

I support Bill's view. However, your bike's pipes are 'burnt' blue, while the ones you are talking about may be just starting to burn golden. This definitely is not any sort of coating. If you are talking about nitriding (AlN) on cutting tools, it is not.

A. Michael.

Bright Nickel plated surfaces do contain sulfur in the form of sulfides which make the Nickel active and receptive to oxidation.

I would consider a Semi Bright Nickel finish from a Sulfur free bath. Or a Dull Nickel bath.

Regards

A. Hello.

I don't agree with Mr. Nurie. Because this situation depends on chrome layer and its thickness and also what temperature has been exposed. Because, if temperature exceeds 300-400 °C, the chrome layer gets deformed and cracked. So in this event, nickel layer appears. Also, in my opinion, I consider this situation depends on number of the cracks at chrome layer. If these cracks number is getting high, this part's corrosion resistance will decrease, so, same event will occur.

Sincerely,

Hello Michael,

A Bright Nickel plated component exposed to high temp. will in the presence of co-deposited Sulfur tend to show symptoms you have described.

Examples of Motorbike mufflers are legion.

Suggest you stay with Sulfur free Nickel, followed by chrome 0.25 to 0.3 microns thick.

Regards

A. Yes, it's dangerous to use muriatic acid if you're not trained in its use. Further, it can destroy the chrome plating, leaving only the underlying nickel plating. If you want a second opinion, I don't think it's a good idea at all.

A. Hi Chris. Thread 26051 claims that it is possible to plate these in such a way that they will not discolor. And the heart of it is, as Asif previously said, to plate a pure nickel with no brighteners or additives, then manually polish it to brightness before chrome plating. Self-leveling nickel was a great labor saving boon, but high temperature operation is a case where the leveling agents are inappropriate. Good luck.

Regards,

A. Muriatic acid will not destroy chrome in watered down concentrations. In fact, I use it all the time to remove scuffed cylinders in engines where aluminum has transferred from pistons to cylinder walls to remove the aluminum and leave the chrome liner unharmed. It works very well and I have never seen, or heard, about Muriatic acid eating chrome. That said, I would think that using it to remove bluing on the pipes as he suggested would be worth a shot. It sounds feasible what with the current flow and the acid reacting with the current. I will be trying it on some old blue pipes I have to see if it works. Stay tuned.

  Thanks Steve, but muriatic acid is exactly the material that plating shops use for quickly stripping chrome. If you have the time for one of finishing.com's longest and most rambling threads, but one of our most informative and entertaining, see letter 12044 How to make hydrochloric (muriatic) acid :-)

Yes, if something is diluted, it won't work as fast as when not diluted; but if I wanted to avoid stripping the chrome, I wouldn't pick the material known for stripping it best. Also, note that the total thickness of the chrome plating on decorative nickel-chrome is often just 5 millionths of an inch -- an amount you'd never notice or measure in your line of work.

A. Hi, Bill. I don't think you will find any such chart since the discoloration depends on the process sequence and the brighteners in the nickel plating as well as the temperature. But there are inexpensive paste-on temperature gauges that turn color at different temperatures.

Regards,

A. Hi Jack. Smarter people than me have suggested on this thread and others that the sulfur-bearing organic brighteners used in the nickel plating are the culprit. But I do believe it, and suspect that you are removing the chrome and topmost nickel with your scotch-brite routine.

Have your plating shop try plating the nickel with no brighteners/addition agents, and manually buff to desired brightness before chrome plating. Good luck.

Regards,

A. Hi again. Trivalent chromium tends to be proprietary, and I'm not aware of studies regarding using it in high heat applications. But since we know that sulfurized nickel plating is a problem, I'd look at that before worrying about something that might or might not be a problem :-)

Regards,