There isn't a word in the car enthusiast's vocabulary that evokes more emotion than the word "rust". It's the automotive equivalent to "cancer". Rust is bad news, no question. It's also a very misunderstood problem, one that can be easily dealt with or at least controlled to preserve an otherwise good 'ol rig.
Preservation and Maintenance:
The most serious type of rust is deep panel rot. The metal actually disintegrates causing holes and other damage. This requires new sheet metal to be grafted into the panel, or complete panel replacement. Why does this happen in certain areas and not others? Prolonged exposure to moisture. The bottom of a fender, particularly behind the wheel well is a common area. Over the years of being driven, dirt and debris accumulates in the bottom of the fender and stays wet, accelerating the rust process. Other common areas are quarterpanels, windshield channels and lower doors. We've all seen rust out.
All cars, whether restored or just beat up old drivers, can benefit from taking a trip to the Car Wash and pressure washing these areas. Put the rig on jackstands, crawl under there and blast that old dirt and debris outta there!! This is the single best thing you can do to preserve whats left of a future project, or keep a finished car preserved.
Dealing With Surface Rust:
Surface rust is actually minor and can easily be dealt with. It's just rust colored metal that doesn't have deep pitting or holes into the pores of the metal. This usually isn't an emergency. The rust/oxidation can be sanded off and a non-porous primer can be applied. Rust Bullet, POR15, or old school epoxy primer can be used to encapsulate what molecules of rust remain in the pores of the metal that can't be sanded out. A cheap easy to use material is plain old Rustoleum. Properly done, this should treat the rust for good.
Pitted Metal:
This gets a little more involved. The rust has penetrated the pores of the metal, but not to the point of rust through. There are materials available that treat this very well. These contain phosphoric acid, which dissolves rust. You can brush it on and it will visibly turn the corrosion black. When the wetness of the material goes away, encapsulate with non-porous primer and that works pretty well. The non-porous primer seals the air/moisture away from the corrosion. The corrosion can't react without moist air to feed it, so it suffocates the rust, and the rust residue lays dormant under the primer.
Handy tip: Use a power drill with a good sharp bit to nibble away any rusty residue. You'll see clean fresh looking metal appear as you grind it out. Cheap and effective!!
Panel Repair vs. Replacement:
As a rule, the OEM sheetmetal parts are much better stampings than any aftermarket parts. This is why i prefer to patch as much existing panel as possible rather than replace. The good news is that there's a huge availability of patch and replacement panels, and there's no shame in cutting up a complete panel for just a couple of patches to use. Think twice before you completely hack off your '69 Chevelle quarterpanel if it only needs 25% reworked, cuz the new one might not fit up. This often applies with trunk floors. If the center section only is rusted, why buy a complete trunk floor and find out that it won't even fit through the trunk opening for installation cuz it's too big?
Sandblasting:
This is in my opinion an expensive impractical procedure. Most of the rotted ares will be cut out and welded up, and any surface rust can be dealt with chemically. There are a lot of hidden hard to reach areas that can't be gotten to with the blasting equipment, so whats the point? Nibble any rust scale away with a drill bit until the metal looks clean, then hit it with primer. Deep rust can only be partially removed anyway, it's not possible to get blasting media deep enough into badly pitted metal to remove every molecule of rust, so don't wig out about rust. Any areas that do require blasting can be spot blasted.
Preservation:
It's safe to assume that if you keep your car in a clean dry garage, or even under a tarp, the weather won't get to it. Don't drive it in the rain, don't leave it outside all winter, and the possibility of rust is zero.
Rust is bad news, but it 'aint nothin' to be 'skeered of.
18 wheeler driving muscle car guru. Residing in the pacific northwest.
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