If your cast iron skillet has rusted on the inside or cracked, then it’s time to throw away your cast iron skillet, this is because cracks or rusty insides will lead to it splitting whilst cooking, this can be very dangerous whilst frying food in oil.
Rust has begun to appear
There will be signs of rust in the bottom, sides, or handles. This is a sure sign that a pan has either been sitting in water too long, or it’s been left in a humid environment, A pan with too much rust will become unusable and need to be thrown away.
However, If it’s only a bit of surface rust, then you can remove the rust using coke.
Some people even try to remove the rust by using heat, but since rust cannot be burned off, this will only make the situation worse.
The texture of the pan is troublesome.
If you’re using your cast iron constantly, the surface of the iron may have become pitted from years of use and cleaning. This is more common in older cast iron skillets.
If this happens, then it’s time to throw away your cast iron skillet as it will impact the heat distribution.
The cast iron is discolored
This happens when a pan is left in direct sunlight or in places that are too humid for extended periods of time. It is hard to clean.
Therefor if your cast iron is discolored, then it may be time to throw it away, you don’t have to as it will still cook food fine, but it certainly doesn’t look nice aesthetically.
So this one is more of a preference.
The iron has oxidized.
This can happen if the pan gets too much heat from an oven or from using high heat on high for a long period of time. (It also can happen when a pan gets stuck in an oven that does not have enough ventilation or if a burner turns on and off frequently) cast iron tends to turn a dark brown when it oxidizes.
The pan is too small for its intended use
Many old cast iron skillets and pots found in attics or garages are just too small for most modern recipes. If you don’t cook large amounts of food or if you only use the pan occasionally, a smaller size probably won’t be an issue.
It’s been dropped or chipped.
While a cast-iron skillet can be durable, there are instances when a little bit of damage will reduce its usefulness; an added problem is that once one chip shows up, you can expect to see more. If you’ve dropped or chipped a pan, try to find someone who can weld it. If it’s too far gone, though, it may be time to replace it.