Sulfide scale catalysis of copper corrosion

The presence of soluble sulfides in a low alkalinity simulated drinking water increased copper pipe corrosion rates by more than one order of magnitude at pH 6.5 and more than two orders of magnitude at pH 9.2. Sulfides caused formation of a thick, black porous scale layer on pipes that did not significantly reduce pipe corrosion rates even after 9 months of exposure. In fact, both the anodic and cathodic reactions were catalyzed when sulfide containing scale was smeared onto a new copper pipe surface. Sulfide scales have a unique ability to accelerate copper corrosion even at pH>9.0, with potentially devastating consequences for copper tube performance in potable water applications.