ESTIMATION OF SHELF-LIFE FROM TINPLATE PROPERTIES

摘要

An equation has been derived to estimate the rate of tin pick-up in citrus products packed in unlacquered cans, incorporating the three properties, alloy-tin couple [ATC), tin crystal size (TCS) and porosity. A direct role for the pickle lag could not be found, it being assumed to influence A TC and porosity.Qualitatively, the equation predicts the general observations, namely a uniform rate of tin pick-up followed by a rapid rise in the later stages. The gradient of the straight line region is thought to be controlled by TCS and porosity, and the position of the rapid rise mainly by A TC. What data there are confirm that TCS and porosity do control the straight line region. In several examples ATC was found to influence the tin pick-up as predicted, fitting the observed results closely. It has been observed, however, that some packings seem to detin in a non-uniform manner, exposing a large area of alloy at a relatively early stage. The effect of ATC is therefore very dependent on the uniformity of detinning, a factor which at present cannot be controlled.