Question

Question:
Will having painted or enameled cans, instead of bare metal cans, retard the problems with iron?

Michele Edge:
The problem is that, when you coat a metal can, you can’t exclude trace metal ions from the surface, and as little as 10 parts per million actually promotes degradation. The other factor is that, if you coat a can, you’re introducing another plastic material that can itself degrade: over the long term, we have problems. Think of library books with sticky-back plastic covers; if you leave them in the drawer for too long, you’ll find that they stick together. That’s basically because you get inter-migration of additives between the systems and, because the additives in one system aren’t compatible with those in the other, breakdown is accelerated.