AN ELECTROCHEMICAL AND SURFACE ANALYTICAL STUDY OF STAINLESS-STEELS AND TITANIUM EXPOSED TO NATURAL SEAWATER

Samples of three stainless steels and titanium grade 2 were exposed to flowing seawater at Port Hueneme, California under natural and reduced light environments. A total of four sets of samples were exposed for times up to 120 days. Open-circuit potential (E(corr)) and electrochemical impedance data as a function of exposure time were used to monitor the electrochemical behavior of the four materials. Surface examination showed a gradual increase in coverage by the biofilm as a function of exposure time. A small increase of E(corr) was observed, independent of exposure conditions and similar in magnitude to that observed in an abiotic, synthetic salt solution. Impedance data remained capacitive over the entire test period. Capacitance values were similar in natural and synthetic seawater. Localized corrosion was not observed for any sample. Pitting scans in 3.5% NaCl, performed as a function of pH, showed that the pitting potential of 304 stainless steel (SS) reached a value of about 0 mV at pH = 2.