# Silver brazing on top of chrome?



## Walt (Jan 23, 2004)

I've got a friend who wants me to add some water bottle bosses to an old 70's vintage road frame - but under the paint, we found what appears (to me) to be chrome. 

I know welding on this stuff is a no-no for fumes reasons, but does anyone know if I can safely/effectively silver braze some water bottle bosses in? A google search says "yes", but I'd love to hear confirmation from someone I actually know here...

-Walt


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## Clockwork Bikes (Jun 17, 2006)

I've heard from other respected framebuilder "no", but with no technical explanation other than it's scary and super toxic depending on the type of chrome. The older the chrome and the less developed the country it's from will increase the odds it's super toxic.


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## j-ro (Feb 21, 2009)

Riv-nut is your friend amigo.


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## TimT (Jan 1, 2004)

I've ground the chrome off with a dremel tool.

Tim


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## A. Spence (Sep 25, 2009)

*Be careful, and safe.*



Walt said:


> I've got a friend who wants me to add some water bottle bosses to an old 70's vintage road frame - but under the paint, we found what appears (to me) to be chrome.
> 
> I know welding on this stuff is a no-no for fumes reasons, but does anyone know if I can safely/effectively silver braze some water bottle bosses in? A google search says "yes", but I'd love to hear confirmation from someone I actually know here...
> 
> -Walt


Walt,

you need to remove ALL the chrome plating in the HAZ of the braze. Every time this has come up over on the frame builders list serve the main concern seems to be the generation of Hexavalent chromium.

Read the first couple of paragraphs of this Wikipedia entry,
Hexavalent chromium - Wikipedia, the free encyclopedia

See also, http://www.osha.gov/OshDoc/data_General_Facts/hexavalent_chromium.pdf

In short, Hexavalent Chromium is generated by hot working chromium containing metals. It is a heavy hitting carcinogen.

Alistair.


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## absinth14 (Mar 24, 2008)

informative...


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## tomswallow (Oct 22, 2011)

*Exposure*

Kinda makes you wonder...

Does your nose or face ever have that steel smell when you're all done with a days work of cutting and welding all that steel?

Aluminum guys have it even worse if I am reading those NIOSH reports correctly.

What about Ti? 
What sorts of gnarl are emitted by that welding process?

Anyone with data on this?


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## mchimonas (Dec 19, 2008)

My day job is that of an occupational medicine physician, and unfortunately, without the assistance of breathing zone sampling performed by an industrial hygienist, there is no definitive way to determine your actual exposure to Cr(IV). The good news is, as a general rule, infrequent, brief, exposures to metallic fumes are generally of little health concern (the exception to this rule would be beryllium—we know from making nukes during the cold war that even brief low level exposures to Be can have negative health effects decades later). Arc welding stainless steel is a clinically relevant exposure to Cr, so routinely welding KVA or 953 would probably result in a higher cumulative exposure than a single episode of placing small braze-ons on a chromium plated bike. Ventilation is key. With good ventilation (and industrial hygiene data), it is often quite possible to skip personal protective equipment such as N95 respirators and the like (PPE is the least reliable way to protect workers). The body is surprisingly good at converting Cr(IV) to Cr(III), which is actually an essential nutrient for glucose metabolism. Generally, the way Cr(IV) makes you sick is by chronic exposure or massive acute exposures. High level acute exposures to Cr is characterized by nasal irritation (of course flux fume exposure does this too) and sinusitis, so if you don’t these symptoms this while brazing chrome plated items a single time, you are probably in the clear. In regards to the Eric Brokovich (however it is spelled) fiasco which caused mass hysteria about environmental (non-occupational) exposures to Cr(IV), well, that was good lawyering and terrible epidemiology (the residents would have had to drink 9L a day of the water to saturate the body’s ability to convert Cr(IV) to Cr(III)). Note that although Erin Brokovich did a great job of gaining millions for herself, the overall effect to Hinckley (however it is spelled) CA was disastrous. Participants of the class action suit didn’t actually win much money (their share after lawers take a big hunk then divided by thousand was small) and now the overall perception is that the town is contaminated (it really isn’t) so the real estate is worthless.


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## mchimonas (Dec 19, 2008)

Oh yes, one other thing, never worked with chrome plating myself, but if you can remove all areas from the heat affected zone by it by wet sanding (sanding would generate large particles, compared to welding fumes, which are harder to absorb, and the wetness mitigates aerozolization), your exposure during heating would be minimal.


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