Microbiologically influenced corrosion on naval carbon steel inside the hull of tugboats: a case study of prevention and control

Microbiologically influenced corrosion (MIC) has a significant cost to many industries, including naval engineering. In this case-of-study, three tugboats developed pitting corrosion in the carbon steel of the inner hulls. Grade A naval steel was used for the hull sheets but the inner side (corroded) showed only two protective layers of paint. The maintenance employed seawater, which ended up in the bilge and made MIC possible. Bilge's waters were submitted to physicochemical, biological and molecular tests. DNA analyses confirmed the presence of Pseudomonas spp. and Desulfovibrio spp. in water samples and, consequently, a MIC mechanism was proposed to explain the corrosion process. In addition, a biocide treatment was evaluated and a new maintenance protocol was recommended. This work highlights the importance of the engineering design to prevent MIC in marine transports and provides some guidelines to treat it.