How to Repair a Large Auto Rust Spot

Rust can destroy any metallic structure and a car is no different.  Even a large rust spot does not have to mean the end of an otherwise well functioning automobile.  Rather than trade in your car, take some simple steps in order to result in a quality and enduring repair that will extend the life of your car.

Rust is the natural enemy of any metallic structure.  Once rust appears on metal, it spreads and weakens the integrity of the structure that it is present on.  In order to make appropriate and lasting repairs, all rust must be removed, before repairs can be made.   

• Sand the rust spot with an electric sander until all of the rust has been removed and the metallic surface is visible.  Be certain that any excess rust particles are removed using a clean, damp cloth.  Failure to do so can result in a gritty surface area and the goal is a smooth, polished one.


• Apply Bondo to the clean, sanded metal surface.  Allow time for the Bondo to harden.  Once the Bondo has hardened, smooth it out with a Bondo file.  When smoothing has been completed, examine the surface for any areas that look too thin.  A second but thinner layer of Bondo should be applied, to ensure structural integrity, and then allowed to dry.


• Use a new piece of sandpaper on your electric sander and lightly sand the surface.  This process can be completed manually if you prefer.


• Examine the surface for any small scratches or pin-sized holes.  Body putty should be applied to these scratches or holes so that spotting does not appear once the surface is painted.  Once the putty is dry, sand the area and then re-apply a thin layer of Bondo again.  Lightly sand until the surface is smooth.


• Apply two coats of paint primer to the area using either a paint brush or a sponge.  Allow for the primer to dry overnight and ensure that it is completely dry before applying a second coat.


• Apply your color of choice to the primed area.  It may be easier to have the entire car professionally painted once the rust spot has been repaired and primed rather than attempting to match the paint to the rest of the car.

In these tough economic times, many of us are in the position of having to do more with less, and so, driving older cars has become commonplace.  Removing and repairing rust spots in a thorough and complete manner can help extend the life of your car.