A STUDY OF COPPER RUNOFF IN AN URBAN ATMOSPHERE

Initiated by the concern in several countries regarding the release of copper from, e.g., roofs, facings and other outdoor constructions, th e present study aims to compare runoff rates with corrosion rates duri ng exposure of copper in an urban atmosphere. The copper runoff rate t urns out to be relatively stable during the 2 year period studied, wit h an average rate per year of around 135 mu g Cu cm(-2). This stable r unoff rate is associated with the formation and dissolution properties of cuprite (Cu2O), which is the dominating copper patina phase throug hout the 2 year period. The copper corrosion rate, on the other hand, is highly time-dependent. It exhibits an initially high value and decr eases with exposure time. As a consequence, the ratio between copper r unoff and copper mass loss is very low in the beginning, around 7% aft er 1 month, and increases with time to reach around 22% after 2 years. With prolonged exposure this ratio eventually reaches 100%, correspon ding to a copper patina thickness that does not change any further wit h time. (C) 1997 Elsevier Science Ltd.