I've done something to several vehicles I've owned over the years including a 92 4x4 Toyota truck that I beat the snot out of for 10 years. What I do is buy several cans of gloss black Rustoleum spray paint. Then cover the body with a sheet or tarp (overspray). I put old cloths on, bandana over the hair, a face mask and a decent breathing mask made to filter paint fumes. Then climb under and coat everything. I coat the heck out of the underside and all suspension components. I'll use the regular spray nozzle on the cans to cover large areas. I also pop out the red spray nozzle plug and push in a red tub like what you find on WD-40 or carb cleaner. That creates a jet of paint that you can send about 2 feet and plaster the hard to get to areas.
I try to do this long before any rust appears and while the vehicle is relatively clean and dry. It has worked great on everything I did it to. With the Toyota Truck, I had one the same year as a friend. We both had the vehicles for about 10 plus years. He never did any rust protection. My truck was sold to a friend, his sold to his mom. So we saw them for the past 15 years beyond the rust protection I did and I can say that it made a HUGE difference. His truck was a rust bucket after 15 years. My truck, minimal rust. Mainly where it was beaten up on the trails underneath. while I had it, I occasionally reapplied more paint for a new "look". The effects were evident though. I live in eastern PA so we see our share of salt, slush, rain and snow. When I get my 2014 Rubicon, I'll be doing the same deal again. Yes, it's messy. I do it in the grass. Yes it stinks for a while. But well worth the $30 in cans of commonly found Gloss Black Rustoleum. Oh, and I'd highly recommend Rustoleum over other brands. It seems to adhere far better than other black paint I've used. Bonds well with whatever I've put it on, even mild surface rust and prevents it from spreading. Good stuff. Look for the big 33% more for free cans.
Most manufactures state that rustproofing is not necessary, but....
I feel it makes a HUGE difference in rust-belt areas like Cleveland. I am in the Northeast Ohio area and had my 2006 TJ rustproofed when new at Ziebart. After 98,000 miles and many winters with tons of road salt, the undercarriage still looks great.
Same with a 2011 JK which had Ziebart when new, and now has 42,000 miles and again, the undercarriage looks great.
I highly recommend Ziebart. I got just the undercoating, not the full rustproofing which consists of drilling holes in doors, etc.
2011, 2-Door Rubicon
The Bigger the Government, the Smaller the Citizen
What I do is buy several cans of gloss black Rustoleum spray paint. Then cover the body with a sheet or tarp (overspray). I put old cloths on, bandana over the hair, a face mask and a decent breathing mask made to filter paint fumes. Then climb under and coat everything.
True. Anybody can crawl underneath a brand-new JK and realize that the tub is only coated by a super-thin coat of primer with no paint. It is shocking, really.
I live on the East Coast of Canada, we get lots of rust here. I have a 2010 that I didn't get undercoated and was starting to see some surface rust and bubbling on the quarter panels. I cleaned up the rust a bit and undercoated it this year. When I bought my 2014 I got it professionally undercoated for $150. There are all kinds of equivalent methods that you can do yourself at home, but when you compare the costs it is one of those things that I think is easier to just pay for rather than to do myself.
The Dealership threw in one of the electronic, cathodic protection modules on my 2014, but it only works on components that it is in contact with. There are too many insulators between components and parts for it to really work effectively so that's why I get it undercoated as well.