The influence of coating defects, cathodic protection and Pseudomonas aeruginosa on the corrosion behavior of EH40 steel

Abstract

The combination of coatings and cathodic protection (CP) is commonly used for corrosion protection of marine metal materials. However, coating failure is sometimes unavoidable in practical application. Previous works have found that effect of CP will be reduced when defects occur, and the presence of microorganisms will significantly affect the corrosion process of substrate metal. However, it remains unknown whether the size of the defect influences the efficacy of CP in Pseudomonas aeruginosa medium (seawater modified Luria-Bertani medium at 37 °C under aerobic condition). In this work, coating defects with diameters of 0.2 mm, 1.0 mm and 2.0 mm were manufactured on surface of EH40 steel using a carbon dioxide laser. The electrochemical and surface analysis results show that CP of −0.85 V_CSE can not protect EH40 steel with different coating defects in P. aeruginosa seawater. Especially for coating defects of 2.0 mm, EH40 steel is polarized anodically. However, CP of −0.95 V_CSE can protect EH40 steel with the different defects. The results of fluorescence microscope and the oxidative stress indicate that the growth and adhesion of P. aeruginosa are inhibited on surface of EH40 steel, which is due to that CP of −0.95 V_CSE exerts stronger oxidative stress on P. aeruginosa. The findings of this study provide valuable insights into the effects of coating defects, CP and P. aeruginosa on the corrosion of EH40 steel in seawater, and guidance for dealing with coating failure in engineering and selecting suitable protection measures for marine equipment.