Microbiologically Influenced Corrosion of copper in potable water installations – a European project review

Abstract

AbstractCopper tubes are considered as material of choice for most domestic and institutional plumbing requirements. However, to a few instances problems have arisen which were shown to involve microbiological activity. The BRITE/EURAM Project “New Types of Corrosion Impairing the Reliability of Copper in Potable Water Caused by Microorganisms” (Contract‐No. BREU‐CT 91‐0452) was launched to examine the interactions between microorganisms and their secreted products and a copper tube surface involving a cross‐disciplinary consortium. A review of this project is reported in this contribution.Based upon chemical analysis of biofilms from failed copper tubes, it was possible to develop model biopolymers of defined composition and well characterised surface adsorption properties to establish suitable electrochemical test procedures. Culture biopolymers showing similar chemical compositions could be produced from a range of copper‐pitting‐associated bacteria. It was possible to demonstrate cation selective behaviour by layers of these relevant model and culture biopolymers.Two linked copper electrodes, one hare and the other coated with a cation selective biopolymer, were shown to establish a corrosion element. The covered areas acted as the cathode whilst the bare areas were anodic. This was also seen in single metal samples with disrupted polymer coatings giving “bare” patches.In anodic areas the corrosion follows a chloride induced mechanism leading to repassivation of the surface. This could also be demonstrated in the original potable water taken from an institutional building affected by Microbially Influenced Corrosion (MIC). Sulphate ions inhibit this expected passivation process. The basic corrosion process appears to follow the chloride model, but this can become overshadowed by the effects of additional anions such as sulphate and bicarbonate.