The research
In the past, a research commissioned by the client into the cause of the corrosion, concluded that the cause of the problem was probably MIC corrosion. We have been asked for a second opinion and to make recommendations for measures that can be taken to reduce the corrosion rate considerably.
Our research has shown that the leaking pipes showed many MIC corrosion characteristic tubercles (wart-like bulges). So-called pitting was found underneath these tubercles. A line formation in the structure of the pipes was observed as well. This line was probably caused by the fact that the pipes were not continuously totally filled with water and therefore oxygen was enclosed. This is an undesirable situation because it can lead to corrosion. In this situation, galvanized pipes offer insufficient protection, since oxygen can attack this protective layer.
Furthermore, samples of the corrosion defects were found to contain high numbers of iron-reducing bacteria that are known to be involved in MIC corrosion processes. Although data on the water conditions show that there are few nutrients in the water promoting biological activity, the regular renewal of the water probably still provides the basic need for microbial growth and activity.
The corrosion products themselves consist mainly of iron hydroxides. This indicates a primary corrosion process involving oxygen. Subsequently the question is raised: how is oxygen introduced into the system? It has been found that the way the water is added to the storage tank, directly ensures that air (and therefore oxygen) is enclosed in the water distribution network.
