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Ant Nest Corrosion Developed on Copper Tubes Immersed in Copper Formate and Copper Acetate Solutions

Immersion tests for phosphorous deoxidized copper (PDC) and oxygen-free copper (OFC) tubes were conducted to investigate an ant nest corrosion developed in copper formate and copper acetate solutions. The test solutions with copper formate and copper acetate concentrations of 0.001, 0.01 and 0.1 mol/L were prepared. The copper tubes were taken out from the solutions at 28, 56 and 84 days for optical and scanning electron microscopy on the cross-sectional surface of the specimens. Typical ant nest corrosion with randomly-branched pits occurred in both PDC and OFC tubes immersed in 0.001, 0.01 and 0.1 mol/L copper formate solutions. On the other hand, hemispherical single pit developed in both PDC and OFC tubes immersed in only 0.1 mol/L copper acetate solution. SEM observation revealed that the corrosion pit area developed in both the copper formate and the copper acetate solutions were composed of metallic copper with fine sponge-like pores.