Marine corrosion of mild steel in particulate media

When in contact with particulate media such as coastal sands or non-cohesive soils, mild steel marine infrastructure is known to be prone to severe localised corrosion. From established localised corrosion theory crevice and or pitting kinetics would be expected under such a scenario. However, field observations indicate the potential prevalence of microbiological induced corrosion but the available evidence is anecdotal at best. Thus, research is being conducted on controlled natural and dosed marine immersed field exposures of mild steel coupons across several permutations of different particle sizes and buried arrangements at the University of Newcastle Taylors Beach testing facility for different periods of time. Alongside the field exposures, long-term electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP) tests are being performed for a better understanding of corrosion initiation and subsequent development with time. Preliminary results indicated that the electrochemical extrapolations greatly overestimated the corrosion rate compared to 2-month field trial measurements, even when ample bacterial nutrient dosing was provided. Reasons and implications are discussed within.