An Experimental Study of Microbial Corrosion and Fatigue-Corrosion of HSLA Steel in Seawater

High strength low alloy steel known as HSLA is widely used in naval construction and ship building due to its capacity to resist to fatigue and corrosion which are considered to be complex phenomena. A study on microbial corrosion in seawater is held on steel plate and compared to specimen removed from a 27-meter naval unit subject to about 37 years of service. Both mechanical properties and microstructural behaviour were studied. The study showed a huge decrease in ductility of steel after exposure to microbial corrosion which is confirmed with Scanning Electron Microscopy (SEM) images. The steel serving for about 37 years showed less decrease in ductility but more in terms of elasticity and this was confirmed with SEM images showing a huge quantity of micro-cracks and corrosion sites. The steel submerged in calm sea water showed a form of pitting corrosion and less fractures.