Corrosion behavior of different stainless steel alloys exposed to flowing fresh seawater by electrochemical impedance spectroscopy (EIS)

摘要

EIS technique was used to study the effect of the seasonal changes of the Arabian Gulf seawater on the corrosion behavior of UNS No. S 30400 stainless steel, UNS No. S 31600 stainless steel and UNS No. S 62800 sanicro 28 that were exposed to continuous fresh seawater for 180 days. Two types of additives (4 ppm of Cl_2 and 5 ppm of NH_3) were also added to the seawater to investigate the effect of residual seawater pollutants on the surfaces of these alloys. At the end of the tests, visual inspection revealed a thin layer of marine micro fouling was spread on the whole surface of the alloys, whereas the corrosion parameters obtained by EIS technique showed a slight increase in the corrosion resistance of the tested alloy, with the decrease of the seawater temperature. In addition, the corrosion resistance was increased for SS 304 and SS316, when 4 ppm of chlorine was added to the seawater, however there was insignificant influence of the ammonia addition to seawater, observed on the tested samples.