Rocker panels? ha ha haI have a 1985 S10 4X4.
The PO had basically replaced every part that was possibly prone to rust with new GM parts.
This was back in 1999
I bought the truck in 2004, it had some surface rust on the chassis.
Well, I tried every "Rust proof" and "preventative" measure there is out there.
Yep, in 2021, the poor truck was riddled with rust. It was so bad, that I had to cut out the rear spring mounts and weld in new mounts/bushings. The bed was ready to fall of.
BTW, I only drove this truck in 2 salt storms (snow) in 15 years.
The salt was already doing it's dirty work.
I should have mentioned - the truck was originally from Wisconsin.
Moral of this???
You CAN'T STOP rust!!!!. If you drive in a salt environment, it will find a way to eat your vehicle.
All you are doing is extending the life of your panels/chassis 5 to 10 years if you go crazy with rust proofing.
I guess that may be worth it in the realm of a vehicle's life.
Living in central NY (serious rust belt) I see 5 year old vehicles with rust started.
OK, I once lived in Massachusetts, and skied in Vermont and New Hampshire almost every weekend.
They used to spray the underside of vehicles with used engine oil, inside panels and trunk. The oil leached out everywhere, but when spring time came, they would pressure wash and clean the panels.
Result? No rust.
I know this is not environmentally (friendly) good, but it was about the only method I ever saw that really worked.
I apologize for the tirade, but I have repaired so much rust and replaced so many panels in my life time, that anyone who says that they can stop or prevent rust is full of it.
Prove me wrong.