Hot-water corrosion failure of a hard-drawn copper tube

Deoxidized high phosphorus copper (C12200, DHP-Cu) is the principal construction element in piping in water distribution systems and HVAC (Heating Ventilation and Air-Conditioning) installations due to its excellent thermal and electrical conductivity, formability, corrosion resistance and antimicrobial activity. However, design and installation deficiencies or aggressive environmental parameters, such as improper water quality, may lead to unexpected failures causing material losses and many times property damage incurring high costs of repair. A corroded copper water tube caused leakage in a hot water hydraulic installation. The leakage was reported after approximately 6 years in service. Tubes were disconnected from a hydraulic installation and samples were taken for failure investigation. Failure analysis findings suggest strongly that the leakage was caused by tube perforation from the inner waterside due to localized pitting corrosion. The main cause of the accelerated tube pitting corrosion was the improper water chemistry (especially high chlorine content and low pH) inducing chemical attack of copper leading to scale layers of cuprite, chlorides and sulfates.