Pitting Corrosion in Copper Tubes in Cold Water Service

Abstract

Exposure trials in different water supplies have been carried out using copper tubes having various degrees of carbon contamination in the bore. On exposure to a water that supports pitting, the electrode potential of highly-contaminated tubes increases to a value greater than the critical potential for pitting. On the other hand, tubes abrasively cleaned with iron or alumina grit to reduce the carbon to a low level have potentials less than the critical value. Experiments were carried out in which uncleaned tubes were transferred from a water that supports pitting to one that does not and vice-versa. The results lead to the conclusion that in a water that does not support pitting, cathodic polarisation occurs to such an extent that the electrode potential never exceeds the critical value for pitting, even in the presence of considerable carbon contamination.