ABSTRACT
The corrosion risk for stainless steel components is not the same in all seawaters, with more failures generally reported in tropical seas. In this study, the influence of biofilm on electrochemical behavior and corrosion resistance of passive films of high-grade alloys was studied in different seawaters, including temperate seawater (France-Brest, North Atlantic Ocean), tropical seawater (Malaysia-Kelatan, Meridional China Sea), and intermediate conditions in terms of temperature (Brazil-Arraial do Cabo, South Atlantic Ocean). The stabilized open-circuit potentials and the polarization behavior of high-grade stainless steels were measured as function of temperature in all the tested field marine stations, providing quantified data and direct comparison on the biofilm-enhanced corrosion risks. Significant differences were measured in tropical and in temperate seawaters in heated conditions above 30°C. In parallel to the monitoring of biofilm-induced depolarization, crevice corrosion of 8 high grades passive alloys was studied with the use of crevice formers specifically developed for tube geometries. Duplex, superduplex, hyperduplex and 6Mo stainless steels tubes have been evaluated together with Ni-based alloys. The corrosion results are discussed regarding the monitored biofilm-induced depolarization measured in the different test conditions.
