UK Monster Owners Club Forum » .: Technical :. » Mods & How To's » Exhaust system tarnish: help is at hand!

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Old 30-01-2020, 12:23 AM   #1
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Exhaust system tarnish: help is at hand!

You can guess how it went: some bean-counter in the bike industry said "Why don't we make exhaust pipes out of stainless steel? No need for expensive and toxic chroming and the riders will thank us cos the pipes will stay shiny forever!"

OK, major rust is no longer an issue but hot stainless of the type used does slowly corrode and will eventually look like it's been plated with cocoa. The best way to slow the process down is to polish the pipes and get rid of the tiny pits in the surface, but even professional polishers hate the job because stainless is so tough. Even polished, the metal will still gain an amber tint but there is a low-effort way to keep it at bay.

Hydrochloric acid magically removes the tarnish, returning the pipes to something that resembles metal. And the best, cheapest source of HCl? None other than Harpic Power Plus Max 10 lavatory cleaner! It comes as a natty green gel that can be painted on. Any drips hitting concrete will rapidly demonstrate its limescale-eating properties but it doesn't appear to harm stainless at all, just removing the tarnish of oxidation. After a couple of minutes, perhaps with a bit of scrubbing, just wash the Harpic off. Yes, you can get busy with metal polish too, but the acid treatment is much easier! Give it a go. Yucky pipes are a major eyesore on a tasty bike!
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Old 30-01-2020, 12:30 AM   #2
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As a Harpic shareholder, I'll second that!

http://www.ukmonster.co.uk/monster/s...ad.php?t=56466
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Old 30-01-2020, 06:54 PM   #3
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I also may have bought some earlier in the week to try this weekend...
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Old 30-01-2020, 07:33 PM   #4
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Had read the same in previous posts and can also keep your u bend stain free so win, win!

Does anybody know if it only works on stainless or can I use it on my titanium pipes too?
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Old 30-01-2020, 09:08 PM   #5
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Does anybody know if it only works on stainless or can I use it on my titanium pipes too?
Hydrochloric acid (up to a 10% solution) is used to clean titanium but it is recommended that it is used with a corrosion inhibitor (such as ferric chloride) to protect the metal. Having said that, an inhibitor is also recommended when using hydrochloric acid to clean stainless steel but, for our purposes, with the frequency we use it and the short time the acid is in contact with the metal, I don't think we need to worry.

If you are concerned, citric acid (for descaling kettles, etc.) used in a 25% solution, or nitric acid in a 10% solution can be used with no need for corrosion inhibitors.
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Old 31-01-2020, 08:14 AM   #6
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Hydrochloric acid (up to a 10% solution) is used to clean titanium but it is recommended that it is used with a corrosion inhibitor (such as ferric chloride) to protect the metal. Having said that, an inhibitor is also recommended when using hydrochloric acid to clean stainless steel but, for our purposes, with the frequency we use it and the short time the acid is in contact with the metal, I don't think we need to worry.

If you are concerned, citric acid (for descaling kettles, etc.) used in a 25% solution, or nitric acid in a 10% solution can be used with no need for corrosion inhibitors.
I use essence of ant: formic acid, for descaling the kettle. Would that work as well? It doesn't come in gel form, so far as I know.
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Old 31-01-2020, 12:07 PM   #7
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I use essence of ant: formic acid, for descaling the kettle. Would that work as well? It doesn't come in gel form, so far as I know.
Acid will act on the oxidation to remove the oxygen, so formic acid would work. Like citric, it is considered to be a 'weak acid'. In contrast, hydrochloric is a strong acid. The pH values, assuming the same concentration of 0.1N(M), are 2.3 (formic), 2.2 (citric) and 1.1 (hydrochloric).

So formic and citric acids will be less effective than hydrochloric, but also less damaging (if that's a concern). If you look at my earlier thread, you'll see that the Australian formulation for Harpic contains formic, rather than hydrochloric, acid, presumably for environmental reasons.

For what it's worth, the active ingredient in Solvol's own Bluing Remover, is hydrochloric acid. It also contains 'secret ingredients', which probably include a corrosion inhibitor.

http://www.ukmonster.co.uk/monster/s...93&postcount=1

Last edited by Luddite; 31-01-2020 at 01:00 PM.. Reason: concentration detail added to pH
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Old 31-01-2020, 01:39 PM   #8
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I went the time consuming route of buffing with a dremel. Took awhile but I preferred the non-chemical route and it gave me the finish I wanted.
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Old 31-01-2020, 04:12 PM   #9
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Took the pipes off mr 1200R and polished using a pukka polishing wheel set, excellent results, only took about an hour. Yes they start to turn brown when hot but five mins with Autosol keeps them bright and shiney
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Old 31-01-2020, 06:34 PM   #10
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Took the pipes off mr 1200R and polished using a pukka polishing wheel set, excellent results, only took about an hour. Yes they start to turn brown when hot but five mins with Autosol keeps them bright and shiney
Same here. Once the pipes are polished its not too hard to keep them up. "Blue off" (eBay) can be a useful thing for the header after a long ride...
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