Can't just clean it you have to season it also.
Needs to be seasoned. Check the net for cleaning and seasoning cast iron. Never ever wash cast iron with soap or in the dishwasher. Hand wash and dry. Do not leave wet.
Needs to be seasoned again. Only clean a seasoned cast iron skillet with hot water and a wire brush. To season a cleaned skillet, you can do it on top of the stove or in the oven; coat with a cooking grease/oil (shortening, oil, bacon grease, coconut oil, etc.) heat until it starts to smoke, turn off heat and let sit till cool, whip clean with a paper towel.
I like to use cooking oil and do it in 2 steps. Either inside& then outside or vice versa. Put in oven @ 250 -300 degrees for 2-3 hrs. Wipe of any excess. No smoke involved.
When you wash it out, put it on back on fire (stove) to let it dry completely ( I usually set my timer for 1 or 2 minutes where I won't forget it) You can spray a bit of oil in the skillet spread it lightly with a paper towel.