A Mössbauer spectroscopy study of the corrosion products formed at an iron surface in soil

Abstract The structural and phase composition of corrosion scale formed in soil on a nail of archaeological origin were investigated layer by layer using the methods of Mossbauer spectroscopy, X-ray diffraction, thermomagnetic and chemical analysis. The following iron compounds were determined: Fe 3 O 4 , α-Fe 2 O 3 ( 2 , FeOOH, FeSO 4 × 3H 2 O, FeCl 2 × 2H 2 O, Fe 3 (PO 4 ) 2 × 8H 2 O and Fe(CO) 3 . Near the iron core, crystallized iron oxides, such as magnetite (Fe 3 O 4 ) and hematite (Fe 2 O 3 ) are predominant; on approaching the surface of the sample, the quantity of magnetite diminishes and virtually disappears. Haematite can be found on the sample surface only in finely dispersed form, while the concentration of iron-sulfur and ironphosphate compounds increases. This model can be explained only by an active bacterial role in the process of soil corrosion.