A few years ago, they received a utility blade that a consumer claimed to have found in a canned tomato product. The case fell to Jim Charboneau, a chemist who has been with the lab for more than 40 years. Through the processor's records, he was able to determine that it had been packed and sealed a year earlier. The blade sported a few stains but still looked new. So Charboneau wanted to see what an identical blade would look like if it sat in a can of tomato sauce for a year and compare it to the sample. He put identical blades in different cans of sauce and sealed them. After a month, he opened one can and found the blade had etching on its surface. After two months, he opened another. That blade had deteriorated more than the first. When he opened another can after three months, he couldn't find a blade. It had been eaten away by the natural acidity of the sauce.
I think I'll pass on the canned food unless there has been a hurricane and I'm stuck without supplies for weeks...or something.