green copper roof

Research activities at the Royal Institute of Technology/Division of Corrosion Science of Sweden have generated a comprehensive picture of the runoff process.

By combining laboratory and field exposures based on a multi-analytical and cross-disciplinary research approach, a runoff rate model has been developed to enable predictions of runoff rates for specific designs or areas. The model considers the importance of the annual concentration of sulfur dioxide in the air, the average rain pH, the annual rainfall quantity, and the degree of surface inclination on the runoff rate process.

copper runoff process environmental impact illustration

It is important to notice that the corrosion process and the runoff process are governed by different mechanisms. The corrosion process is mainly of an electrochemical nature and the process takes place at the interface between the bulk metal and the corrosion product. The runoff process, on the other hand, is primarily of a chemical nature and occurs at the interface between the corrosion product and the atmosphere. Research activities also involve studies on changes in chemical speciation, bioavailability and fate of released copper during environmental interaction with solid surfaces such as concrete pavement, soil and limestone in the near vicinity of buildings. At the site of immediate release, copper is in a bioavailable form. However, it immediately starts to interact with inorganic and organic surfaces in the drainage system and bioavailable fraction is significantly reduced before entering the environment.

The user has the opportunity to test various scenarios using the model. Through the work carried out under the Copper Voluntary Risk Assessment, copper is found to be in general safe for Europe’s environment and health of its citizens.

Corrosion resistant alloys

In order to offer products that generate even less runoff than pure copper sheet the copper industry is investing in the development of special copper alloys. With some alloying elements the excellent properties and aesthetic of copper are maintained, yet the products are even more resistant to corrosion.
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