I have just opened an expired can of beans trying to clean the food stock due to epidemic situation. It expired approximately 6 months. The food looks alright, the outlook of the can doesn't have any sign of rust, looks as if new, the shape didn't transform also due to any form of chemical reaction like food releasing gas to pressure out.
But the wall inside the catch my attention. It has random black spots or pattern. I wonder if anyone have experience? Is this a sign of metal corrosion?