Some Aspects of the Corrosion Behavior of Some Extra Low Interstitial Superferritic Stainless Steels in Chloride Environments under Galvanic Coupling

Abstract The effect of the galvanic coupling of some experimental extra low interstitial (ELI) superferritic stainless steels (SSs) with some less noble metallic materials was evaluated in synthetic seawater under constant strain rate conditions. Times to failure of the SSs are markedly shortened by coupling with Zn, Al + 4% Zn, and Mg, since the corrosion potentials shifted down to the potentials at which hydrogen evolution occurs. Coupling with more noble metallic materials such as Admiralty brass does not effect the stress-strain behavior, and ductile fracture occurs. Coupling with Armco iron does not effect the stress-strain behavior, but scanning electron microscopy (SEM) fractographs indicate the occurrence of hydrogen uptake. Evidence of hydrogen embrittlement (HE) at potentials near −0.7 V [saturated calomel electrode (SCE)] was also found on uncoupled specimens under potentiostatic control. Maximum care must be taken for galvanic coupling and cathodic protection of these SSs, which leads to corro...