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.
No comments:
Post a Comment