Alright, so something weird is going on with my stuff. Since my WSM is out of commission with rusty grates I decided to open up my Kettle (2 years old) and same problem. Grates rusted. This never happened before. Ever.
I can only chalk it up to the mild winter here and above average damp spring. It must have created the perfect conditions to build up crazy rust. I'm just buying new grates for everything and deciding to:
1. Clean them more thoroughly between cooks and oil/season them
2. Store the grates indoors in the winter
I keep them outside because I don't have the room, but I'm looking to build a shed this summer for my house so I hope that alleviates this issue.
Lesson learned.
Do you keep the vents in your grill and smoker open? If not, I've heard that you should so that air isn't stagnant in there.
Though I think I normally keep my grates inside between cooks... I have a box of the stuff I need that I just bring out there.