Commercially pure Cu (Cu), Cu-4.5Sn-0.1Zn, and Cu-9.7Sn-0.1Zn (wt%) were evaluated for corrosion and cation release in modified artificial human perspiration solution. Open circuit corrosion exposures were conducted for up to 130 hours to determine corrosion rate and the fate of Cu and Sn. Released aqueous ion concentrations were monitored via inductively-coupled plasmaoptical emission spectroscopy (ICP-OES). Operando atomic emission spectroelectrochemistry (AESEC) analysis was utilized to elucidate the fate of Cu, whether in oxides or solution and deduce the dominant valence states, Cu(I)/Cu(II), of soluble Cu in artificial perspiration. Sn was not observed as a soluble ionic species within ICP-OES or AESEC limits of detection (LOD). Corrosion products were characterized using grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS), and quantified with coulometric reduction (CR). Cu-4.5Sn-0.1Zn displayed the highest corrosion rates in artificial perspiration, followed by Cu-9.7Sn-0.1Zn, and then Cu. Primary corrosion products were Cu 2 O, with CuCl as an outer solid product, and an inner layer of SnO 2 for Sn-containing alloys. Cu was dissolved as cuprous (Cu +) ions. Minor Sn alloying in solid solution catalyzed Cu dissolution which is counteracted at higher Sn contents by a passivating layer of SnO 2 , achieving complete passivity at 10.3 wt% Sn according to graph theory. Cu-9.7Sn-0.1Zn indicated semi-passive behavior, speculated to be due a SnO 2 layer and close proximity (9.7 wt%) to this critical value for passivation (10.3 wt%). The effect of alloyed Sn as a dissolution promoter for electrochemical Cu ion release, critical Sn contents for passivity, and subsequent implications of antimicrobial function are discussed. Oxidized Zn was not detected above LOD nor demonstrated any measurable effect on corrosion in artificial perspiration.

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 to 80 µA) and time duration at 40 µA (0 to 20 min). Oxide scale formed during exposure to STW was dissolved in a de-aerated 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.