Cast Brass dezincification

[Kram]

If I remember correctly, a weak acid, even warm citric, should start to strip the zinc out of brass and turn a part, a pale salmon pink colour? It is what I expect when I silver braze and soak items to remove the flux.

My recent casting has been sitting in strong acid all yesterday and overnight. Theres a couple pink bits but generally, it hasnt touched it.
Some of this brass scrap had chrome and I assume nickel plating.

Trying to work out what Ive got and the properties. It feels harder to cut and doesnt appear brittle.. melt temp is a bit higher. Could be a useful alloy.. but Ive never heard of Cr or Ni in brass.

With Cr being commonly plated, theres no chance of google returning anything relevant.

 

[Keith 66]

Could be gunmetal, I have seen quite a lot of chromed gunmetal boat fittings.

 

[brightspark]

chrome and nickle would just burn off and leave dross on the top of melt .probably have some bronze in it

 

[Kram]

Interesting. Id guess than if any chrome or nickel were disolved it would be a tiny fraction % and unlikely to be enough for this sort of change.

I dont think any red brass went in but I didnt realise red brass was common for plumbing. Wikipedia implies plumbing brass is leaded?

Gunmetal - Wikipedia

en.wikipedia.org

I had soaked them in citric before hand, they all turned pink. The chromed bits were quite worn so the pink showed through.

 

[Screwdriver]

If it's anything like inquartation of gold, you might need a respectable percentage of impurity for the acid to be able to penetrate the solid. Paradoxically with gold, the more impurities it contains, the easier it is to dissolve it out.

No idea if that's true in this case of course...

 

[mike os]

Probably got yourself some dezincable brass.. contains a small, amount of tin and or arsenic to resist zinc loss ... iirc its known as naval brass?