so a friend of mine bought this bike
http://www.ebay.com.au/itm/110893895090 ... _cvip=true
and he's been asking me all sort of questions to maximize the protection of the frame.
I've recommended a good clean, 1 application of cut and shine, and a few layers of turtle wax.
he still has a few questions i can't answer
how does one look after chrome?
and is there any top coat/clear coat of pain he can put on?
is it necessary?
Help
Vintage frame restoration +Chrome
Chrome is a funny substance to work with. It responds best to regular polishing and waxing. If you lacquer (or clearcoat) over chrome, there are two problems:
1) It don't look nearly as purdy.
2) You prevent the chrome from "breathing", which is a fancy way of saying that you are much more likely to get the bubbling under the chrome, and losing great big pieces of chrome over time. That's the simple answer. The real answer is much more complicated, but we just don't know what process and materials the chrome dippers used. Once upon a time, the chroming process involved dips in three different electrolyte solutions, usually involving a (highly toxic) under layer of copper. These days the process uses materials that are much less toxic, but the finish is not necessarily as good or long-lasting, and there is no longer a copper sacrificial anode. Anyway, regardless of the materials used, chrome is typically less reactive than steel, so when they are in contact with each other, the steel acts as the anode and may rust more readily under the chrome. This is best managed by leaving the chrome uncovered in large areas, so that the gases can escape freely. Another problem with chrome plated frames is hydrogen embrittlement. Apart from the actual problem of making the steel brittle, you can't temper a frame post chroming to remove the hydrogen (or you might melt the brazing), so it sits there waiting for corrosion to set it free, and this may induce water molecules under the chrome over time. Anecdotal evidence seems to imply that the hydrogen atoms are less "trapped" when paint is withheld from the chrome.
By the way, that frame has a Chorus bottom bracket, not a Croce d'Aune one. The CdA bottom bracket had a "flange" on the fixed cup, which is absent on the bike's bottom bracket.
1) It don't look nearly as purdy.
2) You prevent the chrome from "breathing", which is a fancy way of saying that you are much more likely to get the bubbling under the chrome, and losing great big pieces of chrome over time. That's the simple answer. The real answer is much more complicated, but we just don't know what process and materials the chrome dippers used. Once upon a time, the chroming process involved dips in three different electrolyte solutions, usually involving a (highly toxic) under layer of copper. These days the process uses materials that are much less toxic, but the finish is not necessarily as good or long-lasting, and there is no longer a copper sacrificial anode. Anyway, regardless of the materials used, chrome is typically less reactive than steel, so when they are in contact with each other, the steel acts as the anode and may rust more readily under the chrome. This is best managed by leaving the chrome uncovered in large areas, so that the gases can escape freely. Another problem with chrome plated frames is hydrogen embrittlement. Apart from the actual problem of making the steel brittle, you can't temper a frame post chroming to remove the hydrogen (or you might melt the brazing), so it sits there waiting for corrosion to set it free, and this may induce water molecules under the chrome over time. Anecdotal evidence seems to imply that the hydrogen atoms are less "trapped" when paint is withheld from the chrome.
By the way, that frame has a Chorus bottom bracket, not a Croce d'Aune one. The CdA bottom bracket had a "flange" on the fixed cup, which is absent on the bike's bottom bracket.
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