How to tell when to toss cans that have rust on the outside

I scrolled down hoping to find this already, but have to start a new topic. I was going through my cans and found some that have some rust on the lid. These are cans I bought at the beginning of the pandemic. What I think happened was that, in 2020, I was very serious about wiping and washing each can, and somehow I left some moisture on the cans, which then started the rust. Or else, maybe baby wipes aren’t the ideal thing to wipe cans with. Baby wipes with added soap. I am disappointed, but I think I have to toss about a third of the cans that I bought at that time, unless someone has a better idea.  I think the rust probably has not entered the cans, but as soon as I open them with the can opener, I introduce it, right? Live and learn from my mistake, and just leave the cans in the car for three weeks instead, if you are worried about bringing COVID into the house. (I think since then, we have learned more and no one is saying that we need to hose off all our groceries.) Things to consider: 1. I have never had rust before, so it must be the wiping. But, 2. I have not stored in this particular area before so it could be humid, although I don’t think so. 3. ? It’s not a third, it’s a fourth, but still.


  • Comments (9)

    • 4

      If you open the cans carefully, little or no rust will be introduced to the contents.  Even if some is, rust is not particularly toxic . It’s no big deal.

    • 3

      Are both ends of the can rusty or just the lid? If the bottom is ok I would open it at that end when the time comes. I also have a smooth edge can opener which cuts the can below the top edge so less likely that things on the top will get into the food. The smooth edge can opener doesn’t live up to its name in that it creates a SHARP edge when the top is cut off, but I still prefer this type of can opener. Just have to be careful come recycling time.

      • 2

        Some of them only have rust at one end, some have a few spots. None are heavily rusted at all. For some, I might be able to get creative and let the food out at the middle- tomato sauce is one that could possibly be removed that way.

    • 4

      From USDA: “If you see rust on the surface of a utensil such as a cast-iron skillet or knife, remove all the rust before using it.,” which reminds me that I have more than once removed what is probably rust from iron skillets, and never had a problem. https://ask.usda.gov/s/article/Is-food-in-rusted-cans-safe-to-eat

      • 2

        From what it sounds like, your cans will probably be safe to use. Just inspect the cans closely, use them soon and rotate through them, take off labels and look under labels, and open the least rusted side.

        What you are looking for is heavy rust that has eaten through the can and created tiny holes that allows bacteria and air to get into the can.

        If you want to be even more cautious then pour the contents into a bowl, wash out the can and look for rust. You can even shine a flashlight into the can with the lights off and look for any pin hole light beams coming out of the sides of the can.

      • 2

        Henry, that is a great idea about looking for holes with a flashlight. I will do that.

      • 2

        Hardly an expert on this, but FWIW it does seem like as long as you can wipe off / avoid the rust and not ingest it directly, you should be fine. 

        I’ve been in some undeveloped and insanely humid parts of the world where even ‘fresh’ food containers often had rust on them, such as the glass lip of a coke bottle. It was normal for retail staff / restaurant servers to bring you items and wipe the rust off in front of you.

      • 2

        I have wondered, for my long-term food storage which is in my basement – would it makes sense to wipe the cans with a thin layer of food-safe mineral oil to prevent rust? I know I could get a dehumidifier down there (and it doesn’t feel THAT humid), but I probably WON’T, and I have a smallish store of 25-year #10 cans that I’d rather not have to purchase again! (They were pricey but I don’t regret it)

    • 4

      Generally its said get rid of dented, rusty or cans that appear swollen. which is fine in normal times.   But many modern cans are coated with a clear plastic or laquer on the inside thus protecting the tin can from the contents and vice versa.

      So PERSONALLY ( YMMV) I only discard BLOATED or SWOLLEN cans as thats a fair sign of gas being generated by bugs inside the can.

      But slightly rusty or lightly dented cans I open and pour the contents out into a bowl and inspect the inside of the tin,  If the inner coating looks damaged or there is rust inside the tin I discard the food.