Use of Mössbauer Spectroscopy to Study Reaction Products of Polyphenols and Iron Compounds Available to Purchase

Mössbauer spectroscopy was used to study parameters of the reaction products of iron compounds (Fe^III) and polyphenols with hydroxyl (OH) groups in ortho positions. Polyphenols used in the reaction were catechol, pyrogallol, gallic acid, and oak tannin. The Fe-containing compounds were hydrated ferric sulfate (Fe₂[SO₄]₃·nH₂O), lepidocrocite (γ-FeOOH), goethite (α-FeOOH), magnetite (Fe₃O₄), and the carbon (C) steel corrosion products containing γ-FeOOH, α-FeOOH, and Fe3O4. Within a pH range of 1 to 7, all the polyphenols were shown to form with Fe^III sparingly soluble complexes that were mixtures of mono- and bis-type complexes with different Mössbauer parameters. Parameters of each of the complex types were similar irrespective of the structure of the polyphenol used. A mixture of the mono- and bis-type complexes also formed as a result of a reaction between rust-phase components and oak tannin in an aqueous solution. When the reaction occurred on a surface of the rusted steel coated with an oak tannin solution, mainly mono-type complexes were formed. These complexes imparted anticorrosive properties to the converted rust.