Mikrobielle Werkstoffzerstörung – Simulation,Schadensfälle und Gegenmaßnahmen für metallische Werkstoffe: Lochfraß an Flußwasser-Rohrleitungen aus hochlegierten austenitischen Stählen durch mikrobielle Aktivität

Microbial deterioration of materials – simulation, case histories and countermeasures for metallic materials: Pitting corrosion caused by microbiological activity at austenitic stainless steel pipes used for river water Rhine River water used for cooling purposes increasingly causes pitting at circumferential welds in type 321 and 316Ti stainless steel piping. Type 321 is attacked even at ambient temperature, type 316Ti at 35 to 55°C. At these temperatures both materials did not show pitting in the past. Failure analysis and corrosion tests, both in the laboratory and in a pilot, plant (river water circuit), showed that the open circuit potential of stainless steels is shifted into a region of instable pitting resistance by a microbiological effect. Thus, pit nuclei are able to grow even at circumferential joints welded without any visible annealing colours. The actual concept to select cooling water pipe materials, therefore, has to be reconsidered.