Hydrophobicity and Improved Localized Corrosion Resistance of Grain Boundary Etched Stainless Steel in Chloride-Containing Environment

Abstract

Localized corrosion of stainless steels by chloride ions in seawater leads to metal degradation while fouling of marine organisms increases the occurrence of localized corrosion. We describe a simple method to increase hydrophobicity of austenitic stainless steel using grain boundary etching that can also inhibit adhesion of bio-organisms present in seawater as well as increase the localized corrosion resistance of stainless steel in chloride-containing aqueous environments. This paper describes the corrosion behavior of stainless steel as a result of grain boundary etching to achieve hydrophobicity. Potentiostatic polarization on stainless steel 316L in a nitric acid solution at an anodic potential of 1.3 V vs. saturated calomel electrode (SCE) results in a grain boundary etched structure and a Cr- and Mo-rich passive film as confirmed by scanning electron microscopy and X-ray photoelectron spectroscopy. This modified stainless steel 316L surface exhibits enhanced corrosion resistance to a 0.6 M sodium chloride solution. Specifically, potentiodynamic polarization studies indicate that the breakdown potential increases and the sample-to-sample variability decreases. The modified surfaces show a narrow range of breakdown potentials (0.96 to 1.05 V vs. SCE) compared to as-received stainless steel 316L (0.32 to 0.86 V vs. SCE).