Influence of Mg2+ Ions on the Formation of Green Rust Compounds in Simulated Marine Environments

Green rust compounds (GR), i.e., Fe(II-III) layered double hydroxides, are important transient resulting from the corrosion of steel in seawater. The sulfated variety, GR(SO42?), was reported as one main components product layer, while chloride GR(Cl?), more rarely observed. carbonate GR(CO32?), is favored by an increase pH and forms preferentially cathodic areas metal surface. Since Mg(II) abundant seawater, it may have a strong influence on formation GR compounds, particular can be incorporated hydroxide sheets crystal structure. In present work, Mg2+ precipitation reaction GR(SO42?) investigated. For that purpose, substituted, partially or entirely, for Fe2+. then prepared mixing solution FeCl3·6H2O, Na2SO4·10H2O, NaCl, FeCl2·4H2O and/or MgCl2·4H2O with NaOH. followed not 1-week aging period. obtained precipitate characterized X-ray diffraction. It observed green GR(Cl?) magnetite Fe3O4 at detriment GR(SO42?). proportion increased Mg(II):Fe(II) substitution ratio. Without Fe(II), led to iowaite, Mg(II)-Fe(III) compound structurally similar GR(Cl?). forwarded presence cations structure detrimental stability favors other mixed valence Fe(II,III) compounds.