Affect of rechroming on brazing underneath
 

I picked up my Medici from Ron Boi and RRB yesterday. He straightened the fork for me. The chrome is fairly beat up. I asked him who he would recommend I take it to for rechroming. His response was he does not recommend rechroming, as the chrome removal process can leach out some of the braze metal, weakening the joints. Instead, he suggested I either paint the fork or hunt around for a perfect replacement. The former option wouldn't be how the frame was first built (and would still require some sort of chrome removal or at least scuffing). I think the latter option would be nearly impossible.

I respect Ron's advice. After all, he's been at this for a long while. At the same time, other well-respected people in the industry like Joe Bell offer rechroming services, so Ron's perspective must not be held uniformly throughout the industry. I tried a bit of Googling, but all I came up with were questions about brazing over chrome. Any pointers to this issue would be appreciated.

Subscribing.....I'm likely to be dealing with the same issue on a Super Mondia frame/forks I just picked up. Just thinking about it, though, it doesn't seem like it should be a problem. Plating (and de-plating) usually only affects the surface of the metal. If it's a good braze joint, I can't see it being adversely affected much below the portion that's exposed in the plating tank.

That's just a guess, though. I'm sure the right answer is just waiting to be posted.

I don't know. Not sure why removing or adding chrome would destroy the brazing, I don't think there's any heat involved. But I've never bothered with the expensive.

No heat, the dechroming chemical bath is what Ron said was the culprit. (Not sure I understand your last statement.)

Its the same process. They reverse the polarity to remove the chrome rather than deposit it. I meant "I've never bothered with the expense of rechroming."

BTW, the Medicis I remember had no chrome.

I agree, there should be no affect on the brazing as brazing is not appleid with an electro-plating process like chroming, so there should be minimal or no affect on it at all.
Regardng Medicis, models like the "Pro-Strada" usually have chrome on the drive side chain stay, the dropout faces and their fork crowns. IIRC, the lower models (Camino Real and El Dorado) do have less or no chrome though......that's why you really need to be a super great, excellent salesman to re-sell them.....:rolleyes::rolleyes::D

Chombi

Perhaps not all Pro-Stradas have chrome forks, but mine does, as do many of the early hits on this Google Images search.

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Medici went to a fully chromed fork pretty early in the scheme of things for inventory ease and cost. They went with a buy out fork from Tange pretty early. Later they had chrome done to the stays (various amounts) and sometimes to the head lugs as the orders arrived, (give the customer what they wanted).

As to the stripping of chrome and problems, the deal is multifold:

Deplating if done too long will attack the chrome in the blade and or steerer steel.
The braze is most often bronze so would be in danger if the copper layer was also being removed.
After deplating the fork must still be polished before new plating layers go on. Copper, nickel, chrome is the "standard".
Plenty of forks and frames never go this effort though.
The solution used in the entire process of deplating and replating can get trapped in the blades, this is not good.
Condensation while in service later will "awaken" those chemicals which are acidic.
Mix old chemicals with new and trap them in the blades, (usually enter through the vent holes for brazing) is most often the culprit, sometimes there are gaps and or pinholes in the original brazing.
A number of painters will drill a secondary hole inside the fork legs not too far from the crown (often through a reinforcement) to help in the draining and flushing out of the solution in the various stages.
A good chrome plater will be very concerned about this as they don't want their tanks cross contaminated either.
Hydrogen embrittlement is also a factor to be reviewed, there are baking procedures to mitigate this, it just is another step.

Working with a plater to mitigate the issues above is doable, but you will pay for it. It is actually easier to start with a raw fork.

That's very helpful. Thanks you for a clear, informative post. I learned something.

During High school my Summer job was working in a Plating shop. I've seen how old chrome is removed, they use acid. Very, very strong acid, the plater would set a timer so he would know how long to leave it in. If you were to forget a part in the acid tank overnight, it would be ruined or not there at all. Also, I really don't like replating anything thin like a bicycle tubing. Remember the base metal has to be gound and polished, this was already done the first time around. A second round of acid, grinding and polishing would leave those tubes real, real thin. Not something I would do to a bike I would ride, a wall hanger maybe that's it.

Several Bicyle refinishers offer Chroming/re-Chroming services. I'd be more worried about the effects of rust under the chrome then the refinishing process. In the end, I trust the person doing the work.

If chroming can affect the brazing, how did builders apply the original chrome? Us idiots want to know.

It won't affect the brazing when the bike is first built. It's the removal of chrome with acids that hurts everything.

Frequently, but not always the acid solution used as part of the deplating process is assisted with an electrical current. Different acids are used to remove chrome and the nickel layers.

Prior to copper plating, even if the original part is polished first, acid is used to clean and prepare the surface, followed by comprehensive rinsing. The copper is applied, part rinsed, then the part is polished as necessary. A second layer of copper may be applied and buffed again for acceptable appearance. Then nickel, which is the tie layer between the copper and the chrome. Chrome gets applied with anodes strategically placed for uniform thickness. (the inside of a fork under the crown, the back side of a bottom bracket especially near the chain stay bridge are examples of regions where the lack of a well placed anode will result in a poor chrome layer, rough surface and or a bear to buff out) Contaminated tanks can leave a "starburst" on a part and or a "seed" that attaches itself to a square edge, requiring stripping the part again and a redo.

A bicycle painter who has subcontracted a number of chrome jobs should have a good relationship with their vendor. Some will do the buffing initially themselves. You will pay for that effort. One reason restoring a Cinelli Supercorsa well is expensive.

Really? from what I've been told, there are 3 process that could be used: A sodium Hydrochloride bath, which iscaustic to aluminum or a chromic/sulfuric acid & a Hydrocloric acid bath, the latter two reverese the Electroplating process.

Not 100% sure......... but I don't think any of these methods would be overly aggressive to the braze material in the concentrates and exposures that are used for the removal process.

Think about all that chromium locked up in the steel of the tubing, fork blades and stays. The acid does not care where it is consuming the chrome from.

some technical information:

http://www.nmfrc.org/crarchive/jan02a.cfm

I'm referring to the process that I witnessed 40 years ago when I worked at a plating shop. I'm sure it has changed since then.

I did:

The approximate alloying composition of 531 tubing is 1.5% Mn, 0.25% Mo, 0.35% C,

1.5% Mn Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature (often in combination with iron), and in many minerals. Manganese is a metal with important industrial metal alloy uses, particularly in stainless steels.

0.25% Mo Molybdenum is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek Μόλυβδος molybdos, meaning lead, since its ores were confused with lead ores


0.35% C, Carbon (from Latin: carbo "coal") is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. There are three naturally occurring isotopes, with [SUP]12[/SUP]C and [SUP]13[/SUP]C being stable, while [SUP]14[/SUP]C is radioactive, decaying with a half-life of about 5,730 years


4130 frames and gas pipe frames of CroMo may have an issue but that alloy is compounded ( locked up) so maybe it's not effected by electro plating process?

4130 is very close to Columbus. Remember it is an alloy. The chromium is there, but it is not so diffused that it cannot be effected from acid or deplating. Soak a 4130 tube in an acid bath overnight and observe it and or check its mechanical properties.

Mmmmm Medici's are made from Columbus tubes...Hmmmm

Maybe an alternative?
 

Unfortunately the durability of spray-on "chrome" is questionable.

FYI, removing chrome has a more drastic effect if the frame has been "silver brazed" rather than brass.

Anyone here have these guys rechrome their bike frame or forks?

http://home.windstream.net/franklinf...epainting.html

I have read of a few happy paint customers here.