If I am not mistaken I seem to remember reading the specs on GAA and WTR and there was a test with copper strips and apparently some grease types will attack it.
http://www.bing.com/search?q=grease+...D8E4C047A3B090
above is info on GAA
http://www.bing.com/search?q=grease%...40EC18C1166ECA
spec for WTR