A study was made of the various factors involved in the corrosion of plain tin cans containing fruit products. Results of tests conducted to determine the corrosive effects of prune juice and peaches on tin and steel are reported. Data include such items as amount of hydrogen evolved, amounts of tin and steel dissolved, potential relationships, protective currents and polarization characteristics of coupled tin and steel elements.
The shelf life of a plain tin can containing a fruit product such as prune juice is visualized as being made up of three distinct parts. In the first period the steel base is virtually completely covered with tin and the corrosion process occurring is solution of tin concurrently with reduction of depolarizers in the food product on the tin surface. In the second period, a significant amount of steel base is exposed and the corrosion processes are those of the tin-steel couple. It is significant that in this period not only is the steel base protected by the tin, but the rate of hydrogen evolution per unit area of steel base exposed is markedly reduced by the tin coating, This is not due to the inhibiting effect of dissolved tin but to another mechanism. In the third period, the can is completely detinned and attack is on the steel base alone. The life of the can is largely determined before this period. 7.5.2
