Anodic behaviour of tin in citrate solutions: The IR and XPS study on the composition of the passive layer

Anodic behaviour of tin in citrate buffer solution (pH 2−5) was studied by potentiodynamic technique. The current-voltage polarization curves were found to exhibit active-passive transition state; the anodic dissolution of tin in the active region was associated with formation of tin(II) citrate complexes SnHxCit(1 − x)−.. Chloride ions were shown to retard tin passivation due to the pitting corrosion, and this phenomenon was used to increase the passive layer thickness. The composition of the passive layer formed on tin under its anodic polarization in citrate buffer solution in the presence of chloride ions was investigated using infrared and X-ray photoelectron spectroscopies. According to the experimental data, the passive layer mainly represents coordination compound of tin(II) and citrate ions.