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An Introduction to Car Rust Repair & Auto Body Panels

 

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Classic car rust repair can seem like a daunting challenge, especially if you're relatively new to automotive restoration. The best path to take will ultimately depend on where you start. Do you have slight rust in a non-critical area, such as the edge of a fender? Is road salt eating your quarter panels? Are the great outdoors entering your interior from the floor or the roof? Read on as we explain the basics of repairing rust and restoring classic car auto body panels.

Classic Car Rust Repair

In order to determine the best course of action for rust repair, you should first consider how severe the rust is. Paint, trim, and vinyl treatments can hide rust, so it's important to thoroughly disassemble and examine the areas in question to get a clear assessment.
 
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Above: Even if your car looks good at first glance, materials such as trunk liners and carpet can hide rust accumulating beneath.
 

Surface Rust — Cleaning & Treatment

The easiest scenario to deal with is simple surface rust. This shallow corrosion looks ugly and can lead to more severe issues in the future if it's not taken care of. Thankfully, removing surface rust is usually as simple as grinding or media blasting until you reach clean metal. Then, the panel should be primed and painted.
 
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When it's not feasible to strip, prime, and repaint every inch of surface rust, you might consider applying a rust inhibitor and/or rust remover chemical to the surface. These chemicals bond with rust on a molecular level and seal out moisture so it doesn't get worse.
 

Moderate Rust — Patch Panels

If the rust has eaten all the way through your car's sheet metal, or it has weakened the structural integrity of a panel, you'll need to take additional steps to remove it. In many cases, rust will be confined to small areas where moisture and road salt have accumulated, but most of the original sheet metal around these areas will be intact. In this case, patch panels are a good way to proceed.
 
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Our friends at Lowrider magazine recently wrote an article about how they repaired rust found in the trunk of their Impala project car. A previous owner had modified the trunk floor to install a hydraulic system. This resulted in some mild corrosion, as well as a few areas that needed to be cut out and replaced — a textbook example of where patch panels are ideal. Check out their full patch panel installation writeup for more details.
 
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Above: Lowrider staff used patch panels to replace damaged areas in this Impala's trunk.
 

Many cars have body panels of immense proportions. The Impala, or any other full size Chevrolet passenger car can have quarter panels as long as 7-1/2 feet! In these cases, a complete reproduction quarter panel can be fairly expensive.

However, there's no need to replace the entire panel when, typically, only the lower areas around the wheel arches suffer from corrosion. Lower quarter panel patches are great examples of patch panels that can help you save a substantial amount of money in your restoration.

1969-70 Lower Quarter Patch Panels

This passenger-side lower quarter patch panel measures approximately 24" x 89", allowing restorers to replace only the portions of the quarter panel that have been damaged by road debris and corrosion.


Severe Rust — Complete Panel Replacement

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Above: This Classic Industries customer's 1964.5 Mustang, also pictured at the beginning of this article, had quite a bit of severe rust. Thankfully, it was all repairable — read our blog article to see its transformation.
 
Patch panels are great for small problem areas, but if you need to patch more than a few places on a single panel, it may be easier to replace the entire piece of sheet metal. The full-length Weld-Thru floor pan pictured below offers more strength and durability than a combination of sections can provide.

At some point, a patchwork of panels becomes less than ideal. Floors are a perfect example of where the long-term benefits of complete panel replacement are obvious.

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Floors are exposed to more moisture, road debris, and corrosive elements than nearly any other section of bodywork, besides the wheel arches. A patch-and-go approach to floor panels can quickly resemble a jigsaw puzzle. In the case of floor pans, the benefits of increased strength and durability from the fresh metal of a complete replacement panel quickly become obvious.

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What's New in Auto Body Panels?

One of the latest innovations in restoration sheet metal is Classic Industries' new Weld-Thru line. Instead of the traditional black EDP coating, these new sheet metal products are finished with a special silver weld-through primer, offering several advantages.

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Weld-Thru products — such as the inner rear side panel above — require minimal preparation, allow for better corrosion protection between overlapped panels, and promote superior weld characteristics. Heat-zone problems are minimized, reducing panel distortion and allowing better penetration to help compensate for impurities in the original metal.

Important Considerations When Ordering Sheet Metal

We always recommend hiring professional paint and body services for best results. A professional will have the experience required to prepare and install the panels and tackle any unforeseen challenges along the way.

Sheet Metal Work is More Art than Science

Classic vehicles were largely hand-assembled and tolerances are not nearly as exact as they are on modern vehicles with automated assembly. All panels should be test-fitted before final paint and installation. This is to determine whether minor modifications, such as elongating mounting holes, adding additional shims, etc., are required.

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Above: High school students in the SMHS Race Team learned about the intricacies of sheet metal and body work as they rebuilt their '68 Camaro project car.

Light Scarring is Normal

Reproduction sheet metal may have scratches, small dents or other minor imperfections. These are considered normal due to the nature of sheet metal. These issues are corrected during the normal filling, priming, and sanding phase of your restoration.

No Two Vehicles Are Exactly Alike

It is important to note that when you have a vehicle that has been involved in a collision, has been subjected to the stress of racing, or simply shows the fatigue of high mileage and long life, there can be misalignment and even hidden damage within the substructure that can cause fitment issues.

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Where to Buy Body Panels & Rust Repair Supplies

Classic Industries offers a huge selection of auto body panels for classic cars, including small and large patch panels, as well as complete replacement doors, fenders, hoods, and other sheet metal pieces. We also offer a wide range of rust treatment and prevention chemicals. Click the button below to get a free full-color restoration parts catalog for your classic car.

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