Abstract
90Cu-10Ni wafers were corroded abiotically in synthetic seawater solutions containing various concentrations of H+, dissolved O2, and dissolved sulfide. The samples were not disturbed during the corrosion process by stirring or monitoring of the solution chemistry. The Eh, pH, and the concentrations of dissolved O2 and sulfide in the initial and final solutions were measured. Upon removal, the corroded wafers were analyzed by SEM, EDX, XPS, and electron microprobe. These analyses revealed the presence of chalcocite, paratacamite, cuprite, aragonite, and possibly djurleite and digenite on the surfaces of the wafers. Adherence of the corrosion films varied with solution chemistry from those that were nonadherent to those showing good adherence. Significant dealloying of the Cu-Ni alloy was observed. The data suggest a model for this abiotic corrosion process that involves rapid scavenging of dissolved sulfide by copper to form an amorphous or cryptocrystalline Cu-S phase which later recrystallizes into large, well-formed Cu-S minerals. The Cu-S minerals initially formed under reducing conditions persisted even after the solutions became quite oxidizing.
