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Blackening copper and tin plating

Q. Dear sir,

I have come across this site in search for perfection in a particular finish.

1) We have oxidized copper both at room temp and with heat in different chemical, but have not reached the perfect finish required. When done at room temp the finish achieved after heating and drying the component in barrel is a brownish colour. Where as the one required by us is grey-ish in colour, but the luster and smoothness is good. On the other hand if we do it in heated liquid with oxidizing salt the required finish is there but with a different shade and it gets weak if washed in water. Moreover when done a coating of epoxy clear lacquer it fades off. Can you help me in achieving this oxidized finish.

2) How can I oxidize component plated with tin , so as to give it an antique look. Presently we have used sodium sulfide + copper sulphate [on eBay or Amazon]but its not blackening much ?

Pawan Jain
- New Delhi, India
2002


2003

A. Dark grey for copper:
40 gm sodium hydroxide
30 gm ammonium sulphate [on eBay or Amazon]
1 lit water
Hot immersion! 30 min

Black for tin:
200 gm iron chloride 1 lit water
Cold immersion!

Only grease and oxide free objects can be coloured!

Goran Budija
- Zagreb,Croatia