Cast iron cookware has its particular way to take care of as it easily gets rust if you do not dry thoroughly or forget to season it.
Anyway, when the rust is already there, we have to fix it, right?
How to Fix Rusty Cast Iron
If the rust does not show much on your pan, you can skip this step. If it is in the other way, find a bucket, or use your sink which their size fits the pan. Add vinegar and water with 1:1 ratio to a bucket or sink, then put your rusty pan under the solution. Check up periodiocally until the rust starts to peel of (normally can be an hour) But you should not rest it for very longtime as it can damange the pan.
Use sponge or steel wool with warmy soapy water to scrub the rust out.
Rinse and dry
After done scrubbing, rinse with water and dry it right away with tissue paper or kitchen towel.
Since you have scrubbed your rusty pan, some coating part could be peeled off too, you have to re-seasoning to bring the cast iron coating back. You can use vegetable oil to coat both interior and exterior of the pan, the put it in an oven with 177°C for about an hour. Use foil to put under the pan, in case of the vegetable oil drops from the pan. After that, let the pan cool down for 45 minutes before keeping or cooking. If you do not have an oven, you can use stove top too! please check this out how to seasoning. Before using next time, coat the vegetable oil interior of the pan in order to elevate the cooking performance and double coating your pan.
Use & Care
Please be assure than your cast iron pan is completely dry after washing. Coat the pan with vegetable oil thoroughly and keep it in a dry and low humidity place. In the consquece of high level of moist, it causes the rust again.