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oxalic acid bath ruined my chrome frame :(

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oxalic acid bath ruined my chrome frame :(

Old 12-25-09, 08:19 PM
  #1  
billy_boy
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oxalic acid bath ruined my chrome frame :(

help! you're the only ones who can. i recently gave my old vintage bmx a lil overnight soak in wood cleaner/deck crystals (that oxalic acid stuff). i diluted it a lot 50 litres to 1500 grams, although the rust was completley gone parts of my frame were left with this murky cloudy whitish splotchy residue that i cant scrub off with anything

ive tried using fine steel wool and oil but it doesnt rub off. it seems like it's been embedded right in or something. ive read everywhere but no one else seems to have experienced this problem.

any advice would be greatley appreciated. H E L P !

~ bill
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Old 12-25-09, 08:35 PM
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Panthers007
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Use MUCH less oxalic acid should there be a next time. Sounds like you used enough to really acidify the bath - which reacted with the chromium metal to form chromium oxalate. My best advice - as an organic chemist - is to live with it as it's not going to budge. The only chemical reactions that I can think of would likely just make matters worse.

You're best bet would be to use the local Yellow Pages and look for electroplating outfits. Call 'em and see if they would re-chrome the effected area.
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Old 12-25-09, 08:55 PM
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Don't bother rechroming just the effected areas, rechrome the entire frame, it would cost about the same amount anyways.
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Old 12-25-09, 09:37 PM
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I missed the part where it is the entire frame. I agree - plate the whole frame. It will be an easier job for the company you bring it to. No masking need be applied. If you wanted to go nuts - you could plate it in gold, too.
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Old 12-25-09, 11:43 PM
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The problem is you picked the wrong acid.

While oxalic acid dissolves rust (actually converts it into a water-soluble chelate), it also dissolves bare metal at an equally fast rate. A much, much better compound to use is Naval Jelly (phosphoric acid). The reaction is similar in forming oxalates, but phosphoric acid eats away bare metal MUCH, MUCH slower than rust. It also leaves a thin coating of iron phosphate on the surface, which protects against further rust & damage (only temporary).

With either compound, be careful with the handling as the oxalates formed are reactive with the iron in your blood just like cyanide.

Last edited by DannoXYZ; 12-25-09 at 11:52 PM.
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Old 12-26-09, 01:30 AM
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Phosphoric acid is good - and less destructive. Even vinegar - that has 5% Acetic acid - has many fans. Anyone seen the body in the bathtub with Hydrofluoric Acid episode on Breaking Bad? Don't do that.
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Old 12-26-09, 08:28 AM
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Chrome rims are very heavy and very unsafe in wet conditions. Do yourself a huge favor and replace those rims with aluminum rims WRK101, either that or don't ride in the rain if you want to keep the vintage look of the original bike.
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Old 12-26-09, 08:28 AM
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He used 3% 1500/50,000=.03=3% pretty strong. I use Citric acid, it is more forgiving/slower so you don't have to watch it ever 1/2 hour.

Why don't you just spray paint the frame-hide your mistake? Re chroming will be too expensive.
Charlie
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Old 12-26-09, 09:00 AM
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Chrome that has rusted is compromised and on it's last leg to start with. If you remove the rust, it will just come back. Good chrome plating starts with a heavy copper plating to resist rust, then nickel, then chrome as the final step. Removing the plating is a two-step process. The chrome will come off in a matter of seconds in a reverse current caustic bath. After that, the frame would be rinsed and soak for many hours in a special bath that dissolves both nickel and copper. Exactly how long depends on how fresh the stripping bath is. That stripping bath works fine as long as there are no brazed joints, since the stripper dissolves brass, too.

Stripping and replating a frame properly would probably cost far more than the frame, when it was new.

Last edited by DaveSSS; 12-26-09 at 03:49 PM.
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Old 12-26-09, 09:26 AM
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Originally Posted by DaveSSS View Post
Stripping and replating a frame properly would probably cost far more than the frame, when it was new.
That's the essence of the OP's problem right there. Repairing the frame will cost significantly more than replacing it.

The other potential problem is that the chrome plating shop has to know exactly how to handle a bike frame. Chrome plating is not "100% anodically efficient". That means not only chrome is deposited on the frame but some hydrogen is generated too. The hydrogen gets incorporated into the surface, diffuses into the underlying steel and causes "hydrogen embrittlement", which is as bad as it sounds. The plated part can be heated to eliminate the hydrogen and the embrittlement problem but the plater has to know to do it.
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Old 12-26-09, 09:40 AM
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wow i was expecting like one or two replies. thankyooou all you lovely people! god bless you all. i shall read your advice and try out all your ideas. once again, many thanks !!!

i hope i can have the chrome all gleaming and shiny again. i cant believe i read almost every single forum/tutorial going on oxalic acid + rust but they didnt highlight the risks. i shouldnt have used it, i mean the parts where there was no rust before on the bike are now ruined with a milky cloudy haze

https://i515.photobucket.com/albums/t...s/100_0205.jpg


i guess 3 things went wrong:

1. too high concentration like you've guys said
2. the chrome that went milky was (when plated) applied with to low amperage
3. poor rinsing of the part prior to chrome plating (i just dunked them straight in)
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100_0205.jpg (48.2 KB, 235 views)
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