Will copper corrode even if sealed with Incralac?ApproveRejectUn-ApproveSubscribeUn-Unsubscribe
Question asked 2018-05-30 22:18:37 ...
Most recent comment 2018-06-03 14:39:31
Grounds / Priming
Would you mind sharing your knowledge about copper as a surface for an oil painting?
I make artist’s panels for myself and other Seattle artists with aluminum composite material as a substrate. They feature various surfaces.
I’ve been researching copper, and I've just learned that, even if it's sealed properly with Incralac, the copper will only stay shiny for about 5 years, according to a technical expert at Talas. I called to ask about Incralac, and he told me that copper isn’t expected to stay shiny indefinitely, that it’s incredibly prone to corrosion. Because of that conversation, I’ve chosen to stop research and development on copper-veneer panels. I am now reluctant to develop a copper-veneer panel without more assurance from experts that there is a way to preserve its shine that would satisfy artists, conservators, and collectors.
What do you think?
Thanks so much for your time and expertise.
Answers and Comments
Hi Amanda...I have reached out to Dr. Rosie Grayburn on your question as she has had a) extensive experience testing incralac and b) she knows far more about metal chemistry than many of us :) In any case it is good to hear that you have already begun sifting through some of the previous threads on issues (or non-issues) relating to copper. As to the use of incralac and the mounting system you are proposing (copper mounted to ACM) here is what Rosie had to say:
It’s true that like all non-noble metals copper won’t stay shiny forever. Over time, coatings become more porous allowing air/water to reach the metal and cause corrosion, but the better the coating the longer that process will take. Also, Incralac was designed for outdoor use i.e. a much harsher environment. I think Talas’ recommendation for 5-years is based on an outdoor environment. Indoors I believe it would last much, much longer (20 years+). However, If those two metals are in contact, the aluminium will corrode really fast due to sacrificial corrosion but copper will stay ‘safe’ and shiny. That would present a tricky situation...
Dr. Rosie Grayburn
Winterthur Museum - Scientific Research & Analytical Laboratory
While what you write is true, it would be misleading to believe that copper
used as a painting substrate will not corrode in interior conditions. Every
paint sample taken from an oil on copper that I have seen exhibit a blue-green
layer of corrosion at the copper interface. This probably is the result of the
action of the fatty acids in the oil paint and not specifically the atmosphere.
Also, not all copper corrosion products are as benevolent as you suggest.
Copper sulfide is relatively stable but chlorides are very problematic and are
even called bronze disease. Bronze disease is a self-perpetuating problem and
can completely destroy outdoor sculpture.
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