The corrosion mechanism of grey cast-iron yacht keel in marine environment during long-term exposure

In the present study, the corrosion behaviour of a yacht’s keel was investigated. The part had corroded during the COVID pandemic stagnation period when the yacht was kept at the dockyard (shore-water) with a minimum standard maintenance during COVID lockdown time. The corroded scale layers were sampled and characterised to understand the cast-iron corrosion mechanism. The incorporated alloying elements and the formed compounds with their contribution to the corrosion mechanism were investigated. It was evident that Fe2O3 (haematite) and SiO2 (silicon dioxide) were developed on keel’s surface during pandemic’s stagnation period. Those along with consequent oxidation precipitates, inappropriate paint coating material such as copper particles and the existence of detrimental elements from seawater such as S or P accelerated the corrosion rate drastically. The lack of full maintenance for a long time during pandemic is considered to be the main factor for rapid galvanic corrosion occurrence and the keel’s premature failure.