Degradation of coatings for steel in environments susceptible to corrosion associated with fouling

Abstract

Steel piles in a Florida bridge showed severe localised corrosion uncharacteristic of the general corrosion typically found in marine environments. Sampling from the water and the steel pile surface showed presence of bacteria associated with microbiologically influenced corrosion, MIC. Coincident heavy marine growth was observed. The interactions of marine macro- and microorganisms set up conditions where the severe corrosion occurred. The initiation of macrofouling require initial biofilm presence, but the subsequent fouling crevice environments would sequentially promote enhanced microbe growth (such as sulphate reducing bacteria, SRB) to support MIC. Antifouling and antibacterial coatings that have been developed to manage macrofouling may be applicable to prevent MIC. However, long-term durability of the mitigation coating technology can be compromised. The research objective was to identify the efficacy of biocides in an antifouling coating to mitigate microbial activity that are associated with fouling and MIC. Research included laboratory and field examination of a commercially-available antifouling coating in presence of SRB. It was confirmed that degradation of the coating would result in reduced antibacterial and antifouling efficacy and facilitation of SRB growth and marine fouling.