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Electronic Structure of Tin Passive Films and Its Influence on the Corrosion of the Base Metal

Gervasi, Claudio A., Palacios, Patricia A., Alvarez, Patricia E., Fiori-Bimbi, María V., Brandan, Silvia A.
Industrial & Engineering Chemistry Research 2013 v.52 no.26 pp. 9115-9120
buffers, canned fruit, citrates, corrosion, electrochemistry, engineering, fruit juices, oxides, oxygen, pH, tin
Passive dissolution and electronic properties of anodic passive layers developed on tin in citrate buffer pH 3 have been analyzed. This study is relevant to corrosion of tinplate in canned fruit juices. The existence of a direct relationship has been established between the structure and electronic properties of the passive film and the electrochemical reduction of oxygen on its surface. The passive film is made of at least two oxides with different compositions and electronic structures. The inner barrier layer exhibits poorer stability and consequently affords tin lower protection against corrosion. However, due to a more cathodic flat-band potential, this layer is related to large overpotentials for the cathodic reaction during localized corrosion processes, namely, oxygen reduction in aerated media. Dissolution of tin takes place with formation of a dissolved Sn(IV)-citrate complex.