Kashering kalim and small appliances that were previously owned by a non-Jew and therefore used for treif. If I bought say, a toaster oven or a pot or pan at a second hand shop, can they be made usuable?
Regarding the toaster oven, I assume that you mean a small oven to heat up pizza etc. and not what is used to exclusively to make slices of toast. The toaster oven can be kashered using libun kal because nowadays people don’t use the floor of the oven, and the trief things only came in contact with the oven through zeah. The oven has to be cleaned well that there is no grease, rust etc. baked on to the sides of the oven. (This is not at all easy. You might want to try spraying the walls with Easy off etc. and putting the oven on 300oF, then scrub off all the dirt and grime with cold water and soap and a brush). Then it should turned on for 40 minutes on the highest temperature. If the walls of the oven are enamel there are different opinions, but we can be lenient that hagalah is enough.
The oven racks and tray should be switched for new kosher ones, as they will need libun chamur, or put them into a self cleaning oven for the self clean cycle..
Regarding the pot, assuming that it is of metal, will only need hagalah, since it usually absorbs taste though cooking. It should be cleaned well and then kashered by placing it inside a big pot that is rolling boil. (This way the water will not cool down when the pot is placed inside it). Alternatively, you can fill the pot until the top with water, bring it to a rolling boil, and then place a hot object (a rock or ladle made hot) inside the pot so that hot water will spill over and kasher even the top of the walls. Then the pot should be rinsed in cold water.
A pan is more problematic because could have absorbed the trief taste without much oil, and therefore it would need libun chamur. You can put it into a self cleaning oven to kasher it, if they will survive it.
Enamel- Shar Hatzion 451-137, Avnei Nezer Y:D 112-4, Shevet Halevi 2-43 siman 112-4,Orchos Habayis 10-3.PIschei Halacha Chapter 9 ftnt 34.
Pot- OC:H 451-5.Rema 6.
Pan- Y:D 121-4.
Regarding Teflon Igros Moshe E:H 4-7,