Effect of benzothiazole biocide on SRB-induced biocorrosion of hot-dip galvanized steel

In recent times, hot-dip galvanized steel (HDGS) products have been utilized in several engineering construction projects including architecture and structural fabrication due to their excellent durability and appearance. The galvanized Zn layer on steel is designed as a sacrificial anode against corrosion but it eventually fails due to biofouling and chloride-induced degradation. This work is designed to study the extent of damage caused by sulphate-reducing bacterial (SRB) colonization of HDGS surfaces, monitored within defined duration. The biocorrosion mechanism of the metal surface is elucidated by means of electrochemical assessments of associated liquid/metal interfacial phenomena evolved within the bacterial culture period and by monitoring the extent of surface pitting caused by associated biological activities of absorbed SRB cells. The rate of biocorrosion accompanying bacterial metabolic activities for test and control systems are further quantified by weight loss technique in the presence of a benzothiazole biocidal (MBT) additive capable of inhibiting biofilm growth at anaerobic conditions. MBT doped within the SRB-inoculated culture medium inhibited both SRB cellular growth and HDGS pitting, by forming passive antibiotic films on the metal surface. Since sustainable development is an important aspect of modern material designs and construction economics, this work provides a biofilm engineering background to safe monitoring of HDGS products.