Corrosion potential and cathodic reduction efficiency of stainless steel in natural seawater

Abstract

Stainless steels are widely used for different applications in seawater in the oil and gas and desalination industries. It is well known that the corrosion potential of stainless steel shifts to the noble direction (ennoblement) when exposed to natural seawater. The other significant effect of the biofilm on metallic surfaces is a dramatic increase of the cathodic reduction efficiency (e.g. cathodic reduction of dissolved oxygen), promoting the corrosion reactions and increasing the rate of corrosion propagation. Although, this has been widely studied in natural seawater at temperature ranging from 15 to 40 °C, very little is known on the effect of temperature (in a wider temperature range), dissolved oxygen content and chlorination level on the corrosion potential and the cathodic reduction efficiency of stainless steel in natural seawater. In this paper, corrosion potential and cathodic reduction efficiency of stainless steel are reported as a function of temperature (e.g. from 5 to 70 °C), dissolved oxygen content (e.g. from 20 ppb to saturation) and chlorination level (from 0 to 0.5 ppm). The results are discussed in terms of risk for crevice corrosion and bi‐metallic corrosion when coupling to other materials. In addition results from exposure in tropical sea are presented and compared to that of temperate seawater heated at the same temperature.