Electrochemical Behavior of Stainless Steels in Natural Seawater

Abstract

Abstract The detailed electrochemical reactions on stainless steels in natural seawater cannot be predicted without an understanding of the composition of the biofilm. Electrochemical reactions are influenced by biofilm formation and the chemical microenvironment created at the metal/biofilm interface. This was demonstrated by exposing three stainless steel alloys (UNS:S30400, S31600, and N08366) to flowing (15 ml/min) seawater (salinity 32 ‰) collected from the Gulf of Mexico and a variety of sterile chloride-containing media. Open circuit potential was monitored as a function of time and biofilm formation. In some cases, microprobes for pH and dissolved oxygen were used to characterize the chemistry of the biofilm/mctal interface. Scanning electron microscopy (SEM) coupled with energy-dispersive x-ray analysis (EDAX) was used to characterize the biological and chemical nature of the biofilm. A dual electrode system1 was used to determine the direction (anodic or cathodic) and the magnitude of the detailed current resulting from biofilm formation on these alloys.