I've got a few 7.62x39 cans in storage I've avoided opening...

I realize the ammo is more than likely good to go, but sometimes my paranoia gets the better of me.

Has anyone ever opened a can to find the ammo was bad, corroded or something?  

Your ammo is fine.

The sealed cans can sit out in the desert or in a wet environment and as long as they're sealed, the ammo is GTG.

ETA-Some people mistake tarnish for corrosion. Just because a round isn't pretty doesn't mean it's bad.

Not with 7.62x39…. But with some 7.62x25. Some was corroded and cracked at the throat. Some not all. The ammo had a hard life. It was in a can for more than 60years in who know what conditions.

ETA - I still shot it and it was fine.

If your cans are sealed then you are good to go.

Just over a year ago a friend gave me a tin of 7.62x39 that had not been stored well.

One corner of the tin came into contact with dirt that apparently got wet on occassion.

The tin rusted through.

Some - but not all - of the lacquered steel case 7.62x39 inside rusted due to water exposure and ambient humidity.

I've been slowly going through the boxes separating the intact rounds from the rusted rounds. Intact rounds go into an ammo can. I still have 15 or so 20 round boxes I haven't opened.

The few rounds with rust typically have light rust. I've been using a fine file to file those spots to bare metal. These rounds go into another can.

I've found maybe 20 rounds that were rusted so badly that its not worth bothering with them.

This will be ammo I use for function testing and range practice. Or malfunction drills.

I bought a guys Y2K stash he was selling it was 1,000 rounds of 7.62x39 in .50 cans one can had water intrusion and the rounds on the bottom were crusty.  All but 3 went off even the rusty ones shot. They were stored in a basement and he had some flooding