Corrosion inhibition effectiveness of zeolite ZSM-5 coating on mild steel against various organic acids and its antimicrobial activity

Zeolite ZSM-5 coating on mild steel had been assessed for its corrosion resistance property against organic acids, namely, acetic acid, formic acid and citric acid of varying concentrations at temperatures up to 60 °C under stagnant as well as stirred conditions by weight-loss and polarization methods. Biocidal activity of the zeolite coating against Gram-negative bacteria Escherichia coli, Pseudomonas putida, Salmonella typhi and Gram-positive bacteria Staphylococcus aureus by using minimum inhibitory concentration (MIC) was also studied. With zeolite coating, corrosion inhibition efficiency up to 98% was achieved for 6 h of duration of contact between coating and acid solutions. Similar resistance persisted for the duration of 7 days too. Results obtained showed that extent of corrosion of mild steel decreased in the order, formic acid > citric acid > acetic acid. Also as expected, corrosion resistance though only slightly, decreased with solution temperature and concentration. High anti-microbial activity was observed at very low values of MIC (100 μg/mL). In light of reported literature, the presence of the structure directing agent within the channels of the zeolite has been attributed for the high corrosion resistance as well as anti-microbial activity observed here. Thus, zeolite offers a “greener” alternate to chromium and epoxy polymers based corrosion resistance coating.