An Investigation of Copper Pitting Corrosion and Pinhole Leaks

Localized corrosion of copper pipes, or "pitting" corrosion, is a major cause of household plumbing failure. In relatively short periods of time after installing copper plumbing, copper pitting can lead to pipe failure in the form of pinhole leaks. The cost of plumbing repair and the associated expenses of repairing water damaged materials can be excessive for property owners. Additionally, pinhole leaks may go undetected in walls or basements for months, providing an environment for the growth of mildew and mold. Many homeowners elect to replace their entire plumbing system to avoid the hassle of continually repairing damage caused by copper pitting although this may only offer a short-term solution before pinhole leaks in the new plumbing occur. Pitting corrosion of copper plumbing materials in water is poorly understood despite a number of studies on the topic in recent years. Pit initiation has been associated with microbial activity, copper material imperfections, excess carbonaceous manufacturing residues on the pipe surface, water chemistry, stray currents, soldering flux, and others. A number of water chemistry parameters have been postulated to be responsible for the initiation and propagation of pitting corrosion. The parameters include pH, alkalinity or dissolved inorganic carbon (DIC), chloride, organic carbon, chlorine, aluminum, silica, sulfide and sulfate.