• archaeological iron;
  • chloride ions extraction;
  • conservation;
  • electrochemical methods;
  • SEM/EDS;
  • XRD

The conservation of archaeological marine iron artefacts requires chloride ions removal. In this study, the removal of chloride ions was undertaken by two electrochemical methods: the electrolytic and the galvanic reduction in alkaline media. The results were compared with those obtained by the washing and the sulphite reduction methods, under identical conditions. The experiments were performed on samples coming from an 18th century cast iron cannon-ball, found in the archaeological context of a shipwreck, l'Océan, which sank near the southern Portuguese coast, in 1759. The extraction of chloride ions was monitored by ionic chromatography (IC). The results allow to conclude that the sulphite reduction experiments using the mixture 0.5 M NaOH/0.5 M Na2SO3 presents the higher efficiency in the first week, being further overcome by both electrochemical methods. After 40 days of treatment, the electrolytic reduction is the most efficient method.