Kinetics and mechanism of the gold corrosion dissolution in hypochlorite solutions

Kinetics and mechanism of the gold metal dissolution by means of corrosion in chloride-hypochlorite solutions are studied. The dependences of the dissolution rate on the solution pH, sodium hypochlorite concentration, and temperature are determined. Conditions of the gold passivation surface during its corrosion in the studied solutions are discussed. The first-order rate constants of the gold dissolution (k(i) = 0.079-0.4030 s(-1)) at temperatures from 277 to 304 K and others are calculated. The equilibrium constants of the dissolution reactions in acid and alkaline chloride-hypochlorite solutions are different: 1.2 x 10(6) and 2.39 x 10(2), respectively. The activation energy calculated from the temperature dependence of the rate constants (53.43 kJ/mol) evidences a kinetic control of the gold dissolution. Quantitative data on the composition of surface adsorption films, formed by oxidation gold dissolution products, are obtained using the Auger spectroscopy.