A 30‐year review of copper pitting corrosion and pinhole leaks: Achievements and research gaps

Abstract

Despite decades of research, the pitting of copper pipes is poorly understood. This article summarizes the key research findings from 1990 to the present and identifies research gaps. Several lines of evidence suggest that, for soft waters, additional alkalinity or maintaining a pH <8.5 may reduce copper pitting. Phosphate corrosion inhibitors, used to prevent lead corrosion, may also moderate copper pitting in low-alkalinity waters. However, such inhibitors could also exacerbate pitting due to insufficient coverage or could increase biological growth. Biological processes are likely involved in pitting corrosion, and practices to reduce biological growth may be beneficial. The research gaps identified include a need for better benchmarking, the effects of chemical transients (e.g., chlorine burns) and of hydraulic transients (e.g., water hammer), and changing the residual disinfectant from chlorine to chloramine.

Effect of benzotriazole on the existing pits of copper tube in fire sprinkler system

“…1. This could be CuO and Cu 2 O, which were generally formed on the surface of the copper tubes, which are well known to act as protective layers against copper corrosion [ 4 , 9 ]. The region with a high Cl concentration was not clearly visible in the mapping area of tube No.…”

“…As a building plumbing material, copper is widely used because of its excellent corrosion resistance property and ease of installation [ 2 , 3 ]. Although copper tubes provide long-term and reliable services in building plumbing, pitting corrosion induces the pinhole leakage problem [ [4] , [5] , [6] ]. Water leakages cause expensive damage and mold growth inside walls.…”

“…Water leakages cause expensive damage and mold growth inside walls. In the United States, approximately 750,000 pinhole leakages occurred each year in copper tubes, and approximately US$1 billion was spent on their prevention and annual repair [ 4 ]. Building heights have increased with the development of modern technologies; hence, fire extinguishing facilities have also become increasingly important for protecting people and properties.…”

Corrosion Inhibition by Sulfate after Surface Preparation

“…While electropolishing SS with sulfatecontaining solutions improves corrosion behaviour, it may have detrimental effects on metals on which sulfate has the opposite effect, such as copper, which exhibits an increase in pitting in sulfate solutions. 56,57 Several factors were investigated to decouple the main effects of a change in surface preparation method; inclusion site identity, roughness, Fe/Cr, and depth of material loss do not affect the corrosion behaviour as strongly as the % of S in the oxide film does.…”