Cast Iron Grills Rusting After Ever Use?
Please tell me this isn't the case and that I simply haven't treated it correctly?
Used it once, washed it, put it away, only to see it rusted the next day. Same thing happened a day after: used, washed, rusted. Will this happen every single time?
Are you thoroughly drying it, with heat, before putting it away? I do one of two methods depending on what's convenient. I either dry my cast iron on a burner on the stove and use a very thin layer of lard once it's dry, or I put them in the oven at 300 for a few minutes until dry and then wipe on a little lard and leave them to cool before putting away. No rust issues.
If any of my cast iron (like skillets or griddles) can't be cleaned by simply wiping out with paper towels, I use cheap-o salt and a scrubber. Then I put back on burner and get it pretty HOT before another dab of bacon grease... what my grandmother always used. Excess is wiped up with paper towel... don't forget to hit the outside, too.
I assume this pan is new...that being the case, you should not be "washing" it. Once seasoned it isn't the end of the world to use soap on it, but for now you should only be "cleaning" it (without soap). My grill pan is seasoned and I only ever use a stainless scrubber to remove the crud after cooking.
Until your pan is seasoned just scrub clean with whatever it takes to remove the crud (as stated above I use a stainless pad), rinse, dry with a paper towel (you could even heat the pan to dry it, but that isn't necessary), and wipe it with enough oil to shine it up. The oil will prevent the rust you are currently experiencing.
After you cook on the pan for a while it will season itself...so no worries there.