2016 Volume 65 Issue 11 Pages 462-466
Ant nest corrosion of copper occurs in organic carboxylic acid such as formic and acetic acid. Hence, it is predicted that organic carboxylic acid anions coexist with dissolved copper ions inside the pit of ant nest corrosion. In this paper, we present the results of immersion tests of phosphorous deoxidized copper tubes in copper（Ⅱ） formate and copper（Ⅱ） acetate aqueous solutions to investigate the corrosion behavior of copper in the solution containing both copper and carboxylate ions. Ant nest corrosion with irregularly branched tunnels developed for copper tubes immersed in copper formate solution, while a semispherical pit developed for copper tubes immersed in copper acetate solution. Especially, rapid progress of the corrosion in copper formate solution led to perforation of the copper tube with 0.28mm thickness in 26 days. The propagation of this corrosion corresponds to the corrosion rate of 3.9mm/y. Moreover, anodic polarization curves of the copper tube in copper formate and copper acetate solutions were measured. The anodic current density in copper formate solution increased monotonically with applied potential, while the anodic polarization curves in aerated copper acetate solution showed a drop-off in current density originating from the formation of an oxide film.
