The authoritative public forum
  for Metal Finishing since 1989
  

  -----

REQUIRE COPPER SURFACE FINISHING WITH HOMOGENEOUS COLOR

Dear Sir/Madam,

I would like some help on the following issue, concerning copper surface finishing. We have tried to use strong cleaning agent, namely Dynasolve 218 (pH value around 1) to get rid of the silicone stuck on the rim and surface of some thin copper frames. After dip into this cleaning agent for two hours, we will dip the copper frames into alcohol for ten minutes because the cleaning agent is soluble in alcohol. Then we rinse the copper frames by water and blow off the water by compress air and put the copper frames into oven at 80 °C for 20 minutes. This works perfectly and all the silicone has gone. However, it brings another problem where the surface of the copper frame will change color within one or two days, which looks unpleasant. I know it is something related to the oxidation of the copper frame. What we want is more even color on the surface of the copper frame, as long as the color is in the same tune, no matter darker or paler is still O.Kay for us. Could you instruct us how can we do that?

Do we need to neutralise the acidic cleaning agent by some mild alkaline such as soap water before rinsing by water? Or do we need other treatment(s)?

Awaiting your response.

Best regards,

Kam Chuen LEE
- Hong Kong
2001

Your problem indeed is related to the oxidation of copper. You need to passivate the metal surface in order to give it a long term protection.

S. Y. Yuen
- Hong Kong, China
2001

I'm not absolutely sure, but I think that a final dip in 5% acetic acid ⇦ this on eBay or Amazon [affil links] and then drying should give some sort of short term passivation on a fresh copper surface.

Mark Camilleri
- Malta
2001

---

2006

DEAR SIR,
I AM A METAL ARTIST...AND HAVING WORKED IN COPPER , AM AWARE OF ITS QUALITY OF OXIDATION. I WISH TO KNOW HOW KITCHEN OR BATHROOM SINKS OF COPPER MAINTAIN THEIR ORIGINAL SHEEN..AND COLOUR..?

REGARDS,

ANURADHA PRABHAKAR
HANDICRAFTS - LUDHIANA, Punjab, INDIA