ATMOSPHERIC CORROSION OF COPPER IN A RURAL ATMOSPHERE

A field exposure program has been implemented in a rural atmosphere wi th the primary aim of studying the corrosion mechanisms of sheltered c opper. Emphasis has been placed upon the initial corrosion behavior af ter days, weeks, and months. Two starting dates, one in October and on e in April, with different environmental characteristics have been stu died. By using a multianalytical approach combined with environmental characterizations, a picture of the corrosion processes has emerged. I nitially, a film of cuprite (Cu2O) is formed. The rate and growth depe nds mainly on the relative humidity levels. Due to deposition of sulfu r containing species in the atmosphere, mainly ammonium sulfate, noncr ystalline copper sulfate precipitates after days or weeks of exposure which gradually transforms into crystalline posnjakite(Cu4SO4(OH)(6) . H2O) within months of exposure.