First, moisture and carbon dioxide in the air mix to create a weak acid that starts to dissolve the iron. Think about how easy it is to crumble a flake of rust between your fingers, and then imagine that stuff trying to protect you and your loved ones during a car crash.
A stray piece of gravel or a minor fender bender is all it takes to chip a car’s paint, and any iron in the body panels will start to rust as soon as air and water reach the metal beneath it. That means rust spots can be fairly common on used vehicles, particularly if they’ve been driven in a northern U.S. state that uses chemicals and salt to device winter roads.
But if the rusting process goes on too long, it can eat right through the metal, causing holes and allowing body panels to fall to pieces. This is where problems go from cosmetic to dangerous, because modern cars and SUVs rely on these body panels for their structural integrity.
The most serious problems occur when rust gets beneath the car’s surface and within its underlying components. Rust -free body panels boost a vehicle’s structural integrity, but the parts doing the heavy lifting lie under the car’s skin.
Unfortunately, this area of a vehicle is often susceptible to rust -causing chemicals and water, which can accumulate there when a car drives down wet or icy roads. Most customers should avoid used vehicles that show strong signs of structural rust.
CARFAX also recommends getting an expert inspection that includes putting the vehicle up on a lift, to give your mechanic a better view of under body components. You can apply touch-up paint to stone chips, small scratches, and other minor nicks and dings, but truly repairing rust can take several steps, a variety of tools and materials, and quite a bit of skill.
Depending on the size and severity of the rust, blending the repaired area with the surrounding paint may require wet sanding or buffing the surface. Dirt can retain and trap moisture, and road salt, bird droppings, and other corrosive materials will eat away at paint if they’re left unattended on metal surfaces for long periods.
Waxing it on a regular basis (twice or more each year) will add a protective surface to the paint and clear coat. Wash and wax more frequently if you live near an ocean or in an area where highway crews spread salt on the roads to melt snow and ice during the winter.
Also, frequently check the fender liners and other areas under the hood, along the sides of the engine bay, for any standing water. Check the trunk or cargo area to make sure water isn’t seeping past the seals.
Stone chips and other nicks and dings that are left unrepaired can develop into rust spots over time, so it pays to buy some matching touch-paint to cover those imperfections. I also changed the brake shoes, replaced all the drum springs, changed tranny fluid, adjusted bands, new tranny gasket, and adjusted throttle linkage. I have frame rust.
Along the left side of the frame rail beside the fuel tank I have surface rust / flake. Thinking about welding some plate along the frame rail to strengthen it.
I only plow my drive and my folks a few miles away, and then she sits the rest of the year. The majority of the time the horns on the front near the bumper will rot out or the bottom of the C channel near the rear section will be the areas of concern.
I would spray the underside with some good quality annual oil based rustproofing to help keep the rust at bay. Wash is wonderful and coat it again with the oil guard....
I use my truck a little more than you, about 4000-5000 miles a year, and it's a 2006 GM but the same cancer is growing, no flakes yet, but nasty looking. Also, just dumped a bunch of time and money into similar parts, including exhaust manifolds.
In my boat, I want more than three years, so Monday I'm taking it to get the chassis sandblasted and painted by a very reputable local place. It'll be a $1500 investment, but the idea will be I can still pass inspection for years to come.
Otherwise, I'd be approaching the flaky crust stage within a few years, and not be able to get inspection. If you truly want only three years (like you want to buy another truck for sure then), spraying and other undercoating measures will get you there.
In my case, I can't justify another truck for many years, so the investment in sandblasting is well worth it. Took the plow off, tow truck driver straightened it out with the wheel lift, then flatbed'd it.
Everyone bashes GM frames, but I've obviously seen Fords do worse. I have 2 twins and both had misc frame patches in them when I bought them (04's in 08)..........from TX so rust obi wasn't an issue then.
I've also seen plenty of Ford tow trucks crack frames as well. Right near the same spot, but the Dodge was a cab chassis dually, and it split where the double wall started.
My Fords don't surprise me with the load abuse they take.....so I give them credit for holding as good as they do. I've added another spreader this year to one more truck with a similar set of routes.
3 tons+ is asking a lot from a pickup......regardless of how HD the truck may be........and these are the stoutest F350's I've ever seen. The frame issue actually happened while my buddy still owned the truck.
Either sandblast and coat it or deep penetration of oil applied and reapplied. It needs to penetrate to the good metal in order to be effective.
Recently sandblasted some 1/2” thick I-beams on a factory rooftop (not subjected to salt). If that sounds crazy, you should see some I-beams under the bridges we all drive on, that the salt water leaches onto...down right disturbing.
The salt of winter, the humidity of summer and a fair amount of neglect in between can do a number on your truck ’s frame, axles and suspension. As someone who has a dented bed due to a corroded rear leaf spring shackle letting loose, you don’t want to ignore a rust issue.
Given enough time, rust will slowly eat away any exposed iron item bolted to your ride. You’ll need a grinder with wire wheel, wire brush, 5-in-1 scraper, painter’s tape, masking paper, rubber gloves, and some sort of paint gun or empty spray container.
Paint brushes get the call as well, to help evenly distribute the thicker areas of the rust reformer (once it’s applied). Available by the quart (of which a typical truck will require about two containers per coat) or pint, Rust Mort can be had for roughly $25 to $28 per quart ($15 to $18 per pint) and you can get your hands on it via Summit Racing or O-Reilly Auto Parts.
Depending on the condition of your frame, axles, and suspension, you could easily spend an entire 8 to 10-hour day removing rust, old paint, or undercoating). For tighter areas, we relied on a 5-in-1 scraper, wire brush and even sand paper.
Once you’ve cleaned up the frame, axles, and suspension to the best of your ability, pressure wash everything and allow it to dry. Obviously, you won’t want everything underneath the truck painted or hit with rust reformer, so take time to cover up things like exhaust tips (or the entire exhaust system), diff covers, the transfer case and the transmission.
Whether you’re using a gravity feed paint gun, a Hudson sprayer, or a repurposed tire shine spray bottle, the bottom line is to apply your rust reformer in every exposed area to get the same result: seal the rust and prevent the spread of it. There are a lot of automotive paints on the market, but we’ve always used Rust coleus’s Gloss Protective Enamel (In 7779830).
During the prepping process, rusted metal particles will be flying everywhere so do yourself a favor and put on those dorky safety glasses you’ve got stowed away in your toolbox.