Abstract
In tinplate cans filled with sulfur-containing foodstuffs such as fish and meat, tin reacts with H2S and HS- ion produced by thermal decomposition of content during pasteurization and sulfide stain is formed inside of cans. The effect of tin crystal faces, tin oxide and passivation film by cathodic dichromate treatment on the sulfide staining was studied and noted on the mechanism of sulfide stains by transmission electron microscopic techniques.
The summary is as follows:
(1) Sulfide stain on tinplate cans packed with tuna was identified by electron diffraction as stannous sulfide SnS. The degree of tin sulfide stain depend on tin crystal orientation, and the closely packed (010) and (110) planes are more stable against sulfide staining.
(2) Tin sulfide staining is prevented by passivation film, the staining on passivated tinplate starts at the sites uncovered with passivation film and tin oxide is peeled at the interface of tin and tin oxide by growth of SnS. When nuclei of stannous oxide SnO are formed during baking of lacquer, the staining starts at them.
(3) The sulfide staining is inhibited by formation of passivation films at defect sites of tin oxide. And stannic oxide SnO2 on tin layer act as barrier layers against the formation of SnS.
