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.

Electroactive Bacteria Associated With Stainless Steel Ennoblement in Seawater

“…In this study, we were interested in gaining further insight into the bacterial community of the stainless-steel surface immersed in seawater and its electrochemical activity in relation to the potential ennoblement. Previous studies have shown an inhibition of the ennoblement activity above a critical temperature (Scotto et al, 1986; Dupont et al, 1997; Martin et al, 2003; Gümpel et al, 2006; Thierry et al, 2015). In our setting, this critical temperature was between 38°C and 40°C, above which the ennoblement was inhibited despite the continuing presence of bacteria.…”

“…Kinetically, an increase of the cathodic reaction rate can also result in an increase of the OCP. Previous works have demonstrated that surface microorganisms increase cathodic reduction efficiency (Johnsen and Bardal, 1985; Holthe et al, 1989; Audouard et al, 1994; Zhang and Dexter, 1995; Mollica and Scotto, 1996; Rogne and Steinsmo, 1996; Le Bozec et al, 2001; Larché et al, 2011; Thierry et al, 2015). Other reactions such as manganese oxide reduction in freshwater (Dickinson and Lewandowski, 1996; Gümpel et al, 2006) and the formation of hydrogen peroxide could also contribute to the increase of the OCP as it is a stronger oxidant than oxygen with a higher redox potential (Landoulsi et al, 2008b).…”

“…While the mechanisms of ennoblement are still discussed, the seawater temperature has been identified as a critical parameter. Ennoblement is a temperature dependent process, undergoing a complete inhibition above a critical temperature around 40°C in temperate seawater and freshwater (Scotto et al, 1986; Dupont et al, 1997; Martin et al, 2003; Gümpel et al, 2006; Thierry et al, 2015). This critical temperature seems to vary with geography as it is 32°C in the Norwegian and Baltic sea (Bardal et al, 1993; Mattila et al, 2000).…”

Role of mixed species microbial community biofilms in microbially influenced corrosion

“…In the preliminary experiment (Chapter 3 section 3.2.1), following immersion in seawater, the OCP of super duplex stainless steel (SD) increased and reached ~ 270 mV in 2 d and remained stable for 7 d. This was consistent with experiments in tropical environments, where SD initially showed ennoblement at approximately 300 mV in 3-5 d of immersion and remained stable until 50 d, (Thierry et al 2014). Xu et al (2015) also observed potential ennoblement for SS316L immersed in natural seawater.…”

Electrochemical analysis of a microbial electrochemical snorkel in laboratory and constructed wetlands

“…S1B, curve a), the potential of the electrode reached values comprised between +450 and +650 mV vs SHE. Such potential values in natural (non-sterile) waters are often interpreted as oxygen reduction potential of biocathode developed on stainless steel [28,29]. Note that no corrosion was observed during the three months of this experiment.…”