A Beginner’s Guide to Underbody and Body Panel Restoration

If you are starting out on your restoration journey, Rustbuster is here to help. On this page you will find simple guides to some of the most common restoration tasks, with information on the products you need for success.

We don’t just produce and sell one-off products: we bring you systems for addressing the issues you are likely to encounter during your project. These systems have been tried and tested over many years of auto restoration to give superb results and protection for your vehicle.

To help you, we’ve put together guides to three common scenarios below. As you read through these system guides, click on the orange product links to find out more or make a purchase.

Scenario #1 – Vehicle underside showing signs of rust with flaking paint/underseal.

1. Wash down the vehicle’s underside using Rustbuster Chlor-X salt remover followed by Rustbuster SP10 detergent and then rinse with deionised water. It’s important to remove grease and salt first, as otherwise when you move on to the next step you could push grease and salt into the pores of the metal.
2. Remove as much loose rust and failing coatings (paint or wax) to get back to a sound steel surface. Use scrapers, wire brushes, drill/grinder attachments or a specialist MBX metal blasting tool. The aim is to get back to clean steel where possible, although it is likely you will still have areas of surface corrosion. You may decide to leave in place any existing paint coating that passes an adhesion test.
3. If the steel’s surface has been perforated, you may need to consider welding in a patch or replacing the panel (see scenario #3 below). Assuming that the steel is not perforated, proceed to step 4.
4. On areas where surface corrosion is still visible, apply Rustbuster Fe-123 converter to the surface, working it well into the steel. When the Fe-123 has fully reacted with the oxides it will turn black. Read our guide to using Fe-123 Rust Converter for more information about this process.
5. Once you have finished your surface preparation, you should ideally give the area to be painted a final clean with Pre-Paint Panel Wipe.
6. Now you are ready for paint! Apply two coats (by brush or spray) of Rustbuster EM121 Rust Proofing Paint direct to clean steel, over the Fe-123 converted steel, and over an existing coating that passes an adhesion test. EM121 can be left as a finish or over painted with car finish colours, stone chip or wax.

SAVE money on these products with our Chassis Restoration Value Pack.

STAY SAFE with the right Personal Protective Equipment.

Scenario #2 – Areas of the vehicle’s body work are showing signs of rust, e.g. blistered paint bubbling on wheel arches etc.

1. Wash down the vehicle’s paint work using Rustbuster Chlor-X salt remover and Rustbuster Safer Degreaser. Note that in the case of body work repairs (i.e. not the underside) we recommend using Safer Degreaser rather than SP10. This is because SP10 in too strong a mix can potentially remove paint.
2. Open up the paint blister with a paint scraper or similar tool, being careful not to damage too much of the good surrounding paint. This will reveal the extent of the rust.
3. If the steel’s surface has been perforated, you may need to consider welding in a patch or replacing the panel (see scenario #3 below). Assuming that the steel is not perforated, proceed to step 4.
4. Remove all the rust and old failed paint back to a sound steel surface. Use abrasive paper to ‘feather edge’ the good paint with the bare metal.
5. If there is still some rust pitting deep in the steel you may want to consider the use of Rustbuster Fe-123 Rust Converter. Apply to the steel surface very lightly, working the solution deep into the steel. Overlap the edges of good paint by only a millimetre or so: focus the Fe-123 on the rust, not the paintwork. When the Fe-123 has fully reacted with the oxides it will turn black. Read our guide to using Fe-123 Rust Converter for more information about this process.
6. When the treated areas have fully cured (hard black) lightly sand to remove any nibs, and ideally give the area to be painted a final clean with Pre-Paint Panel Wipe.
7. Apply a coat of Rustbuster Custom 421 Epoxy Body Primer. This can be rubbed down when dry to the level of the existing paint. Further coats and/or filler can be applied over the Custom 421 where necessary and sanded until you have achieved a smooth surface.
8. Once your preparation is complete, the area is now ready to take a coat or two of your body colour to complete the repair.

Scenario #3 – Tackling areas that need weld repairs.

1. Follow all of cleaning and preparation steps above to reveal the state of the corrosion.
2. Cut out all of the corroded steel.
3. Sand back the area surrounding the hole you have cut out to bright clean steel.
4. Prepare a patch the size of the hole, sanding both sides of the patch.
5. Apply a coat of Rustbuster Weld-Thru Primer to all of the prepared surfaces – on edges of the hole in the body panel and both sides of the patch.
6. Weld the patch in place.
7. Either paint the inside of the patch if accessible with Rustbuster EM121 Rust Proofing Paint or, if the inside is a hidden cavity that does not give you access for painting, spray a coat of cavity wax behind the weld repair.
8. The front of the repair can either be painted with Rustbuster Custom 421 followed by body colour if on the bodywork, or Rustbuster EM121 if on the underside of the vehicle (in which case follow by applying a seam sealer to the weld lines).

Can we be of more help?

You’ll find more information and tips in the Rustbuster Blog and extensive Rusty’s Tips library.

And of course, do please contact us for help in choosing and using suitable products for your restoration project.