The anodic dissolution of copper alloys: Pure copper in synthetic tap water

The anodic dissolution of pure copper was investigated in naturally aerated synthetic tap water (STW) by in situ atomic emission spectroelectrochemistry (AESEC). This technique measures the Cu dissolution rate directly and the formation of Cu scale indirectly by mass balance between the anodic current and the dissolution rate. The conditions investigated include the effect of applied current (0-80 μA) and time duration at 40 μA (0-20 min). Oxide scale formed during exposure to STW was dissolved in a deaerated citrate buffer solution (CBS) and followed by in situ AESEC as well. A mass/charge balance confirmed the predication that most Cu(II) species are soluble and are released into STW, leaving behind a Cu2O film as an insoluble product on the surface. Ex situ Raman spectroscopy and grazing incidence X-ray diffraction analysis (GIXRD) also corroborate this conclusion. A quantitative analysis of Cu(I) and Cu(II) species vs. applied current and vs. time during a galvanostatic pulse are presented. At open circuit the oxidation product is essentially Cu2O; soluble Cu(II) is favored as anodic polarization is increased. A kinetic analysis suggests that the dissolution mechanism involves simultaneous Cu dissolution and film formation rather than a sequential mechanism.