Why you may want to undercoat your aluminum F-150
There are at least a dozen fan forums set up to address this issue and hundreds of different answers. The questions come from all over the U.S. and Canada. J.B. asks “I just purchased a 16 SuperCrew about a week ago. I live in Ohio where salt is used on the roads during the winter and I'm curious if I should get the truck undercoated. I've heard the trucks come treated from the factory, but I don't know if that's accurate. Is it worth getting undercoated? I really don't want to see rust underneath in two years.”
A truck owner named Rick from south east Michigan sounds like his information is direct from Ford. Rick says, “For corrosion protection, the entire frame is immersed in an e-coat solution and an electric charge is applied. The result is a durable protective shell that bonds with the steel and inhibits rust, even in hidden areas. Ford engineers went to great lengths to inhibit galvanic corrosion, which can occur when steel (and some other metals) comes into contact with aluminum along with moisture. Specially coated bolts, clips and isolated body mounts prevent steel and aluminum from coming into contact.”
Rick adds, “Extensive corrosion testing was also done to ensure the tough adhesives used in the body can stand up to the elements and extreme temperature.”
Aluminum doesn’t rust but it can corrode, getting white spots on it. Steel obviously can rust and often does regardless of the corrosion protection, especially is high-salt areas.
Owners like this one responding to Rick, are very concerned. “That's all true, but have you been under your truck to look at it up close? I did and when I bought the truck brand new there was already a light flash rust on the front of the rear diff housing and a few welds on the frame that had rust spots. This was in the summer, before any salt or snow.”
A 2016 F-150 owner who goes by FoxTrot says, “I just ordered a Gallon of "Fluid Film Undercoating" and the equipment to spray it. This stuff never dries so it won't trap moisture. It does need to be re-applied ever year on exposed areas. And it creeps into the seams, nooks and crannies.”
There is a lot of concern that drilling any holes into the panels to apply rust proofing could void the factory corrosion warranty. “I got the Corrosion Free treatment done at a Canadian Tire in Windsor. They did a great job and spent about 1.5 hrs spraying my truck! I told them to not do any drilling at all. They just stuck the wand into some of the existing drain holes in the doors and door sills and sprayed what they could. I'm not that worried about the AL corroding and didn't want to void the factory corrosion warranty, in case there is some sort of recall, etc.”
The various truck owners seem to like Fluid Film, Krown and Corrosion Free as the best undercoating for the aluminum F-150s.
Torque News reporter Marc Stern warns that the vehicle must be properly prepared for the undercoating to work, if not the coating can do more harm than good. Stern says "I followed them closely and they seemed great. That is until they started to be applied poorly because the vehicles were never prepared right. Vehicles have to be super clean and super dry before you can even think of putting that junk on there. All that happens is if there is any moisture, the moisture is trapped and it begins to eat away at the metal, after it has a nice dinner on the clearcoat, cover coats, primer, electrophoeretic paint and then yum, the bare metal."