Study of the Performance of Different Corrosion Resistant Alloys (CRAs) Used in the Manufacture of Fasteners in the “Splash Zone” under Cathodic Protection

Abstract The present study evaluated nickel-based corrosion resistant alloys (CRAs), used as fasteners in simulating “splash zone” region under cathodic protection (CP). The CRA’s were submitted to crevice corrosion and the influence of CP was assessed electrochemically. The testing apparatus was an automated system synchronized with a potentiostat that was able to keep the CRA’s in wetting and drying conditions in intervals. The temperatures were 40 °C and 70 °C. To understand the effect of the CP on these alloys once the crevice corrosion was formed, three different potentials were tested: -800, -900 and -1100 mV (Ag/AgCl), synthetic seawater was used as corrosion medium. The Wet&Dry tests were performed during 168 h by monitoring open circuit potential (OCP) right after the drying step and before electrochemical impedance spectroscopy (EIS) measurements. Electrochemical results pointed out that CP presents a deleterious effect on all CRAs tested in which crevice corrosion was previously formed. EIS indicated that regardless of the CP potential or temperature tested, cathodic protection reduced the impedance moduli for all alloys tested. Also, the values showed that more negative the CP potential, greater the reductions in impedance modulus.