Marine Vibrio spp. protect carbon steel against corrosion through secreting extracellular polymeric substances

Abstract

The protection of marine materials against corrosion using marine bacterial biofilms is a promising strategy. However, little is known about the mechanisms of this attractive corrosion prevention method. In this work, the corrosion behaviors of X80 carbon steel (CS) in the presence of three different marine Vibrio species were studied. The results demonstrated that all the three Vibrio spp. displayed significant corrosion protection with a weight loss reduction of up to 68%. Moreover, their corrosion prevention performance was tightly related to their abilities to form biofilms, which was in the order of Vibrio sp. EF187016 > Vibrio alginolyticus > Vibrio parahaemolyticus. To further investigate the corrosion prevention mechanism caused by marine biofilms, the extracellular polymeric substances (EPS) of Vibrio sp. EF187016 was extracted and added to 3.5 wt% NaCl for abiotic corrosion testing. The results suggested that the EPS inhibited corrosion, which means EPS can play a significant role in corrosion protection by biofilm.

Roles of Microbial Extracellular Polymeric Substances in Corrosion and Scale Inhibition of Circulating Cooling Water

“…Furthermore, big capacitance arcs and one-wave peaks in Nyquist and Bode plots (Figure ) indicated that time constants such as protective film formation and charge-transfer process should be presented, and there are at least two similar relaxation times of time constants during the corrosion of A3 carbon steel. , As shown in Figure a–c, the semicircle diameter in the Nyquist plots was significantly larger than that without s-EPS (Figure a), indicating that the charge-transfer resistance and corrosion inhibition rate were increased with s-EPS . Additionally, by a comparation with Figure a′, the increased peak heights of Bode plots in Figure b′,c′ indicated that protective films were formed with the addition of s-EPS, leading to corrosion inhibition of A3 carbon steel in circulating cooling water …”

“…35,36 As shown in Figure 5a−c, the semicircle diameter in the Nyquist plots was significantly larger than that without s-EPS (Figure 5a), indicating that the charge-transfer resistance and corrosion inhibition rate were increased with s-EPS. 17 Additionally, by a comparation with Figure 5a′, the increased peak heights of Bode plots in Figure 5b′,c′ indicated that protective films were formed with the addition of s-EPS, 33 leading to corrosion inhibition of A3 carbon steel in circulating cooling water. 37 The experimental data were fitted according to the actual situation; impedance spectra were analyzed using an equivalent circuit.…”

“…As shown in Figure S3a, the all E OCP values shifted appearing to the negative direction and no obvious difference was seen at the end of 6 days immersion. , Therefore, electrochemical testing was required to reflect the actual corrosion inhibition effect. Figure a–c and Figure a′–c′ show the change of Nyquist and Bode plots of A3 carbon steel in circulating cooling water without and with s-EPS over time.…”

“…As shown in Figure S3a, the all E OCP values shifted appearing to the negative direction and no obvious difference was seen at the end of 6 days immersion. 33,34 Therefore, electrochemical testing was required to reflect the actual corrosion inhibition effect. Figure 5a 5) indicated that time constants such as protective film formation and charge-transfer process should be presented, 34 and there are at least two similar relaxation times of time constants during the corrosion of A3 carbon steel.…”

Extracellular Polymeric Substances and Biocorrosion/Biofouling: Recent Advances and Future Perspectives

“…EPS can adsorb on the metal surface and form a biofilm, which acts as a protective layer, hinders the transmission of oxygen, and separates a metal surface from a corrosive environment, thus, metal corrosion is inhibited [ 53 , 54 , 124 , 125 , 126 , 127 ]. The negatively charged functional groups in EPS, such as -NH 2 , -COOH, -C-O-C, and -OH, first adsorb positively charged metal ions to form complexes.…”