Analysis of leakage failure in a domestic hydraulic installation assisted by pitting corrosion of water tube

Deoxidized high phosphorus copper (C12200, DHP-Cu) is the principal construction material in hydraulic and heating ventilation and air-conditioning installations due to its excellent thermal/electrical conductivity, formability, corrosion resistance and antimicrobial properties. However, design and installation deficiencies or aggressive environmental conditions, such as improper water chemistry, may lead to unexpected failures. A corroded copper water tube caused leakage in a domestic hydraulic installation close to the sea coast area. The leakage was reported after short-time period in service. After installation the pipeline was not in continuous operation and remained unused for approximately 3-6 months per year. 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 waterside by severe localized pitting corrosion. The main cause of the accelerated tube pitting corrosion was probably the improper water quality (high hardness and electrical conductivity) but the potential for an aggressive environment created by substances, such as chlorides and organic compounds, could not be excluded. © 2009 ASM International.