In general, the stainless steel alloys are resistant in drinking water qualities excelling by a low
metal release and long lifetime. A number of cases from fire protection systems and drinking
water installations have been described in order to document how metallurgical (welds, heat
affected zones) or geometrically (crevice in press fitting connections) sensitive areas of EN
1.4301/1.4401/1.4404 can corrode in low chloride drinking water types. The mechanisms are
still not fully understood, but a number of parameters have been highlighted, including
ennoblement and stagnant conditions, indicating that microbially influenced corrosion is
taking part in these corrosion failures occurring within less than 2 years service. The failure
mode is pitting and crevice corrosion leading to leaks and rust stains on the outside of the
installation.
To predict and prevent these corrosion failures better understanding of the mechanism would
help, however, dedicated studies are rarely conducted in connection with industrial failure
analysis. Application of relevant microbiological techniques could be included for better
documentation and in order to investigate the possible effect of the microorganism.
Cooperation between research groups and exchange of experience is necessary, if the
understanding should improve. Presently the best tools available for prevention therefore are
awareness of the risk, combined good practice regarding water quality, installation, and
process conditions.