Corrosion phenomena on aluminium alloys spontaneously mitigated in natural seawater

Although aluminium alloys are known to exhibit generally good corrosion resistance in natural seawater, they may encounter generalised and localised corrosion phenomena. In this work, an aluminium alloy casted referring to the AA 5083 composition was tested in artificial vs. natural seawater exposed to the photoperiod. SS 254 SMO samples were exposed to the same environments acting as indirect indicator of the bacterial growth by OCP (Open Circuit Potential) ennoblement. OCP and SEM (Scanning Electron Microscopy) data obtained from aluminium alloy revealed that the corrosion phenomena encountered in the NaCl reference solution, mainly consisting of mud crack scaling and rare crystallographic pits, were attenuated in natural seawater. The inhibiting effect probably depended on the organic molecules adsorbing from the bulk and produced by settling bacteria as well.