Buy a heavy duty cover and use it. If you are in a 4 seasons climate and have room, store it inside during the winter.

We live in Florida and the grill is a built in an outdoor kitchen. Covers don't stay on very well.

Find a cover with velcro ties at the bottom

i was hoping for a product that can be applied to the stainless steel as a corrosion preventive...WD40 ???

If it is made of the correct stainless steel for appearance purposes, and the welding rod is appropriate, it should never corrode. If any staining occurs, use a phosphoric acid wash (read the directions) that may be obtained from an auto parts store supporting the body shop trade.

P.S. Original WD-40 is a water displacing oil for machine stamping protection. It might have some property for rejecting water on the SS, but(!), do we know what it will do when heated?

No corrosion on true stainless steel. If you need to polish I always go back to the old faithful Brasso.

I long ago learned that the 'less' is stainless is very literal - it stains about 20% less. But still stains. I clean it with water and maybe the 3M stainless wipes occasionally but otherwise just call whatever is on there... patina from a well loved (used) grill.

I have a built in Fire Magic Grill, (charcoal), I had it since 2012, never had any corrosion. Like I said, it does require a deep cleaning at least a couple time a year. If I use the brasso and a ton of elbow grease, I can get it pretty close to new and mirror finish.

A zinc based spray can be used on clean (grease, silicone, and rust free) steel as a corrosion protectant, usually as a primer, but I suspect that zinc spray won't chemically bond to stainless steel, and might have difficulty over wide temperature ranges, so perhaps it is best used on legs that aren't subjected to heat and that aren't really stainless steel (and that will be painted over).