Impact of pH, Dissolved Inorganic Carbon, and Polyphosphates for the Initial Stages of Water Corrosion of Copper Surfaces Investigated by AFM and NEXAFS

Nanoscale studies at the early stages of the exposure of copper surfaces after systematic treatments in synthesized water solutions can provide useful information about corrosion processes. The corrosion and passivation of copper surfaces as influenced by pH, dissolved inorganic carbon (DIC) and polyphosphate levels were investigated with nanoscale resolution, to gain insight about changes in surface morphology and the composition of adsorbates. Information regarding the surface morphology after chemical treatment was provided by atomic force microscopy (AFM) and the corresponding chemical composition of treated surfaces was obtained with near-edge X-ray absorption fine structure (NEXAFS). Changes in the surface topography of copper samples were readily detected within only 6 to 24 hours of exposure to water solutions. Topographic views of surface changes are presented to compare the growth of adsorbate layers that take place during the evolution of mineral deposits. Slight changes in the pH and concentrations of phosphates in the water samples have a substantial impact on the rate of growth and composition of surface deposits. These studies provide insight on the mechanisms and resulting chemical constituents that lead to surface passivation or corrosion of copper, simulating conditions that occur in water distri-