Some X‐ray photoelectron spectroscopic measurements on Passivated Tin in some neutral media

Some ESCA measurements have been carried out on the anode film formed on BDH Sn foil by the potentiodynamic technique up to 2.5 V (SCE) in (i) phosphate buffer, pH 6.7, (ii) 0.1 M KCl, 0.1 M Na2SO4, pH 6.6, in order to identify the elements, and possibly also some compounds, present in the film. The results in phosphte buffer indicate the presence of: (i) Sn(II) and Sn(IV) oxides and hydroxides, (ii) tin phosphate species probably (HPO4)2−, (H2PO4)−, and insoluble phosphate complexes and (iii) evidence is given for the formation of soluble Sn species containing OH or phosphates before the beginning of passivity. The results in chloride solutions indicate the presence in the anode film of Sn, O and Cl in various states of combination such as: (i) Sn(II) and Sn(IV) species (oxides, chlorides and some hydroxides, (ii)) adsorbed oxygen and water, and (iii) basic or oxysalts or complexes involving Sn, O, Cl, and K. The results in Na2SO4 solutions indicate the presence in the film of Sn, O, S, and Na in the form of: (i) Sn(II) and Sn(IV) oxides and hydroxides, (ii) Na2SO4, other un- identified S species, and possibly also traces of PbS (from traces of Pb present in the Sn foil), (iii) adsorbed oxygen and water, and (iv) basic or oxysalts or complexes involving Sn, Na, O, sulphate and other unidentified S species.