Chrome Plate Removal

[HH @ 24]

Hi All, I'm installing reclaimed sanitary ware in my bathroom and the taps will be brass. The sinks and bath currently have chrome plated plug holes, etc and I want to try to remove the chrome to reveal the brass underneath rather than replace with new brass fittings. I have tried soaking one plug hole in brick acid which had some effect (see photo). The right side is after soaking (looks like maybe copper layer under the chrome?) and the right side I used an abrasive metal disk on my drill, which revealed the brass under the copper but making a bit of a mess. But it hasn't really removed much of the chrome. Does anyone have any idea how to remove the chrome plate completely? Thanks!

 

[Flyfisher]

I don't know if there's a chemical method that would discriminate between chrome and brass so I suspect you'll have to use some sort of mechanical method to remove the chrome. The good news is that the chrome plating is likely to be very thin but the bad news is that chrome is a very hard metal so it you'll need something fairly aggressive to remove it while being careful not to take too much off the underlying brass.

If the plug surround is fairly flat then it might be possible to use a lathe or a milling machine to remove the thin layer of chrome, but I appreciate that not everyone has access to an engineering machine shop!

I think you'll have to persist with the abrasive approach, after which you should be able to polish the underlysing brass by using increasingly fine abrasives until a final application of Brasso or similar.

 

[Toby Newell]

Yooo... send off to get sand blasted and polished and preferably passivated.

 

[Toby Newell]

Your item is brass, overplated with copper, then nickel then chrome.

HCl will remove the 'soft' chrome and eventually the nickel but will not remove the copper. HCl will attack the zinc in any exposed brass. Nitric acid will dissolve the copper, but also the copper from the brass. Whilst producing toxic brown NO2 gas.

So. Buy some gauntlets, face shield and a half mask respirator with ABEK fume filters and work outside. Best of luck.

Or do the above. As fly says, mechanical abrasion is safer. You can do yourself, search for 3M Cubitron 947A ceramic abrasive, P120 grit, that will munch easily through the chrome, after that 3M P400 Silicon carbide wet and dry, then P1000, or Scotchbrite grey. Finish with T cut, then Brasso or Autosol.

(FYI Conservator working with brass since 1986, also, metallurgist with 6 months in an international electroplating laboritory. I used to dip my hand into 1:1 Hydrochloric acid when preparing samples for plating, have used Copper Cyanide when underplating and Hydrofluoric Acid when prepping Aluminium microscopy samples and dipped my hand into pH14 Potassium Hydroxide at 60°C, I'm no chemical prude, take it from me, you don't want to be using Nitric acid, not only does it eat skin, produce toxic Nitrogen dioxide, it is one of the top oxidisers and has a habit of spontaneously combusting anything it touches, including pretty much anything organic and many gloves)

 

[Toby Newell]

You can get the 947a on Roloc discs, but you would need cloth belts and cut up for the inside. Abrasive blasting is the way to go really. Once the chrome and nickel are removed, the copper comes off quite easily.

It's quite a lot of work to do yourself, like hours per item. Quite satisfying. If you have a mini grinder / buffer, you can use calico mops with buffing compound, search for Dialux, is quicker than the T cut / Autosol method.

 

[Toby Newell]

You can also use zirconia belts. Zirconia Alumina and Ceramic alumina are pretty much the top abrasives you can get. They can be about 5x as aggressive and durable as regular DIY abrasives.

 

[Toby Newell]

Back in the day I used to use a Wolfcraft drill holder on a workbench, with a calico mop on a spindle, bit janky but can take anywhere. It's quite messy tho.