Waterlogged woods and iron reinforcements extracted from archaeological shipwrecks were studied. The corrosion mechanisms of the reinforcements were investigated by analyzing the corrosion products using a multi-technique approach. The woods contained pyrite and greigite. The reinforcements showing different degradation states were corroded into siderite, chukanovite, mackinawite, pyrite and greigite. Then, two half-nails were soaked in neutral and acidic Na 2 S solutions. Mackinawite precipitated only in neutral conditions. Through this study, the natural mackinawite-to-pyrite evolution process induced by a long-term exposure to sulfides is highlighted. This work also shows that iron sulfides can result from complex processes implying other sulfide-sensitive phases.