Unexpected pitting of copper pipes in drinking water installations has appeared mainly in public buildings (often in hospitals) at a small number of places around the world (for example, Germany, Scotland, Saudi-Arabia). Experience and scientific based knowledge about pitting corrosion of copper does not indicate a remarkable susceptibility in the respective drinking water installations. Because substances of biological origin were mixed with the solid corrosion products, the following hypothesis was generally accepted: microbiologically influenced corrosion (MIC).

Though the mechanism of MIC is by no means clear in detail, promising countermeasures have to be developed, substantiated and introduced into practice to protect existing installations. In this paper, the arguments for qualified actions are described and, when available, the success of these measures are mentioned. It can be stated that the likelihood of MIC in copper can be reduced to technically acceptable or even to negligible values by a combination of some well-known methods of corrosion protection.