Pitting Corrosion in Copper Tubes in Cold Water Service

Copper and Copper Alloys

“…There is general agreement that type 1 pitting occurs in hard or moderately hard waters and is favored by water with high sulfate content; failures occur most rapidly in water of fairly low chloride content. Pitting occurs when carbon residues, which arise from the breakdown of lubricants during bright annealing, are present on tube bores [41,42]. The importance of deposited carbon films in pitting of copper is widely recognized.…”

“…Carbon residue on copper alone, however, is insufficient to produce pitting. Studying the influence of carbon contamination in the bore, Cornwell et al [41] found that the electrode potential never exceeded the pitting potential in water that did not support pitting, even when high carbon contamination was present. On the other hand, when tube specimens contaminated by carbon were immersed in aggressive water, pitting was observed, but abrasively cleaned specimens did not pit.…”

“…Electrochemical protection: Following Cornwell et al [41], Lecointre et al [51] and Pourbaix [52] observed that if the tube surface can be maintained at an electrode potential lower than the protection potential of copper, existing pits cannot grow and new pits cannot form. The redox couple Fe 2 þ -FeOOH can maintain the tube surface below this protection potential, and this protection process should remain valid for copper alloys (e.g., brass) and waters containing chloride (e.g., seawater and brackish water).…”

Efecto de los componentes del agua de mar durante el fenómeno de corrosión por picaduras del cobre

“…CuCl [1] En dichos sitios o puntos de nucleación de la picadura, el CuCl sufre una hidrólisis formando CU2O, el cual precipita en la superficie del metal como lo expresa la siguiente reacción: 2CUCI + H2O =» CU2O + 2HCI [2] La reacción catódica que soporta la disolución anódica es la reducción de oxígeno:…”

“…Cornwell et al (2) propusieron el siguiente mecanismo de picaduras para el cobre en agua de mar, donde los iones Cu+ y Cl" reaccionan en sitios determinados siguiendo la reacción:…”