Dechlorination and Phase Transformation of Corrosion Product β-FeOOH on Iron Cultural Relics

Rules of dechlorination and phase transformation of corrosion product β-FeOOH on iron cultural relics are reviewed. The effect on β-FeOOH should be concerned in the dechlorination treatment of iron cultural relics. Commonly used NaOH or alkaline sulfite solution immersion methods can usually remove most Cl^- adsorbed on the surface of β-FeOOH crystals, but it is sometimes difficult to entirely remove Cl^- and transform β-FeOOH. However, residual Cl^- is mainly bound in the crystal tunnel structure, which does not directly promote further corrosion and deterioration of iron cultural relics. Electrolysis and high-temperature (hydrogen and hydrogen plasma) methods are more thorough in the dechlorination and phase transformation of β-FeOOH, but they are only suitable for some iron cultural relics and with some risks. In recent years, new dechlorination reagents and methods, such as TMAH, plant extracts, subcritical fluids, and microbial methods, have been developed continuously, which have certain advantages and are expected to be used in the conservation of iron cultural relics.