Investigation on the electrochemical evolution of the Cu-sn-Pb ternary alloy covered with CuCl in a simulated atmospheric environment

Abstract

• The long-term electrochemical evolution of Cu-sn-Pb alloy with CuCl patina is studied for the first time. • The impedance value increases at 0 ∼ 3 h, decreases at 3 ∼ 7 h, and recovers after 7 h during EIS monitoring. • The fluctuation of impedance value is related to the conversion of CuCl to Cu 2 O and the cycle of chloride ions. Nantokite (CuCl) layer induces severe corrosion of bronze by its active reactivity to copper alloy. To further understand its corrosion mechanism, this paper investigated the electrochemical evolution process of the Cu-S n-Pb ternary alloy covered with a CuCl layer by continuous electrochemical impedance spectroscopy (EIS) monitoring. And the EIS changing mechanism induced by dynamic Cl - circulation and the transformation of the CuCl were also discussed. The results showed that two extreme impedance value points, the 3rd and 7th hours, were observed during the evolution process of the CuCl layer within 48 h. The decrease of the impedance value at 0 ∼ 3 h was mainly affected by the reaction of CuCl hydrolysis forming a Cu 2 O film, while the increase of impedance value at 3 ∼ 7 h was affected by the reaction of copper attacked by chloride ion. After 7 h, the impedance value of the Cu-Sn-Pb alloys continued to increase due to the formation of a dense cuprous oxide layer and chloride ions migrating into solution.