Don’t let your classic crumble! Kim Henson advises on how to preserve its structure...

The single biggest enemy of virtually all classic cars is rust. The chemical conversion of solid steel to a weak mess of ferric oxide (rust) takes place gradually, of course, but it can creep up on you unawares as it  takes its toll on your vehicle. If the damage is left too long, rectification can cost a great deal in terms of time/cash, and can even threaten the continued existence of your car.

Rust forms when moisture and air are allowed to reach unprotected steel, and the process is hastened by the presence of sulphur dioxide from the atmosphere, and impurities such as road salt.

It therefore follows that if the metal is isolated so that contaminants, air and moisture cannot reach it, rust cannot get a grip.

Fortunately this is not difficult, although some effort is required…

The first obvious step to protect the car is to keep it as clean as possible, by regularly washing (and re-polishing as required) the upper bodywork, and by periodically hosing/power-washing off accumulated debris from the underbody. If using a power washer, take care not to keep the water pressure at a reasonable level; if the pressure is set too high, this can be responsible for removing paint.

Mud (combined with road salt, on classics used during the winter months) can become trapped within crevices around the under-wing voids and ‘chassis’ members. This mud tends to retain moisture too, so already in place are the ‘dangerous’ elements required to create rust, and these are just waiting to start gnawing away at your classic’s structure, given half a chance. If there are any chinks in the vehicle’s protective armour of paint or underbody coatings, rust WILL start.

Having carefully cleaned the car, on top and underneath, allow it to dry fully, then carefully inspect the state of the underbody paint/sealant coatings. Take your time and inspect the WHOLE of the vehicle’s structure. If any scratched areas are found, or any sections where the protective coating has peeled away, abrade away any surface rust, and ideally treat with a chemical rust killer, before touching up the paint/underbody.

If the surface of the original protective coating has deteriorated over wider areas, it’s best to rub down and re-coat the whole surface, to provide effective long-term protection.

Note that if holes/weak metal are discovered in structural underbody areas, before applying fresh protective coatings, repairs must be carried out by welding in place repair sections (in each case seam-welded all the way around the perimeter of the repair plate).

Moisture tends to accumulate within enclosed ‘box’ sections around the vehicle, eventually resulting in rusting from within. Due to access problems, it can be near-impossible to apply protective paint within such cavities, but rust-resisting wax/oil based fluids can be introduced by means of a hand pump, or ideally under higher pressure from a spray gun.

If using a compressor and an air-fed spray gun assembly, make sure that the compressor is capable of providing enough pressure to pump the fluid you are planning to use. Depending on the product, this can be relatively thick in nature…

Long lances and various spray tips are available specifically for the introduction of anti-rust products within enclosed areas. In many cases factory-made apertures can be used for feeding the spray lance where it’s needed, but if you do have to drill any access holes, protect their edges by painting, and use plastic or rubber grommets to plug the holes on completion.

When treating the insides of doors, sill assemblies, etc. ensure that all drain apertures are unobstructed before and after wax/oil fluid treatment.

A wide range of protective products is available today, with the different fluids possessing varying properties for specific jobs. For example, some are low viscosity types and feature a built-in ‘creeping’ action to percolate into the tiniest apertures around the body shell. Others have a thicker consistency, and some have a ‘self-healing’ facility, so that in the event of a minor disturbance the surface will re-seal automatically. Check all information available for each product, before you buy. The supplier should be able to help, and/or the website of the maker may provide invaluable information.

It’s a good idea to make rust prevention part of your classic’s ongoing maintenance programme. In addition to frequent cleaning (and polishing if required) the exterior of the vehicle, it is important to regularly re-check the condition of its underbody structure, and to re-apply paint, underbody sealant or preservative fluid as appropriate. Ideally do this at least every six months, to help ensure the long-term survival and enjoyment of your car.

HOW EASY? ****

This work is not difficult but it can be messy (definitely wear old clothes and shoes!), and you need to allow a whole day to carry out rust prevention work around the car.

USEFUL INFORMATION

1. When applying wax/oil based fluids, choose a warm day if possible (with ambient temperatures above 15 degrees C/60 degrees F). Alternatively, before you apply the product, carefully pre-warm the fluid container by placing it in hot water. This helps the fluid to flow easily through the application equipment.

2. Note that excess rustproofing fluid (escaping from drain apertures, etc.) can be collected in tins or trays for re-use.

3. On completion, clean out all applicator lances and jets, to prevent semi-solidification of the preservative fluid within them. Consult the information provided with the product regarding recommended cleaning agents; in many cases white spirit can be used.

Dec21-28How1  1. Surface rust on the underside of the vehicle, the floor pans and also the boot floor, can be abraded away using silcon carbide (‘wet or dry’) paper. Wear protective goggles. Vacuum/wipe away all dust	Dec21-28How2 2. The application of a rust-resisting paint to prepared areas (as depicted in our previous photo/caption) will help to preserve the metal. Some products require two coats for optimum protection.	Dec21-28How3 3. Surface corrosion on external panels and in body seams needs to be carefully eradicated by abrading away, then treating with an anti-rust primer, followed by conventional primer and top coats.
Dec21-28How4  4. For full internal treatment of enclosed cavities and box sections, protective wax/oil based preservative fluid can be introduced under pressure, using a lance with a multi-way jet assembly, like this.	Dec21-28How5 5. Especially vulnerable to rusting are the splash panels and associated metalwork behind the front wheels, also the sill assemblies. Clean off dirt, then apply preservative fluid.	Dec21-28How6 6. Many classic cars have ‘jig’ points used at the factory on the production line. To preserve these (and the steel above them), apply wax/oil based fluid to all internal surfaces.
Dec21-28How7  7. It is essential to preserve the structures around spring supports, and often these incorporate complex profiles and a multitude of small enclosed cavities. ‘Fill’ these with preservative.	Dec21-28How8 8. Moisture can collect behind running gear components. Dry out the water (a fan heater can be effective), then coat the metal by introducing a protective fluid that will ‘creep’ into all corners.	Dec21-28How9 9. By their nature, suspension components such as wishbones and support bars, etc. are in exposed positions and original paint coats are usually thin. Protect by re-painting with an anti-rust coating.
Dec21-28How10  10. Underbody members can harbour condensation which can cause disintegration from within. Apply a wax/oil based preservative, having first dried out all moisture (again, a fan heater is ideal).	Dec21-28How11 11. On many unitary construction vehicles, the longitudinal underbody beams effectively form part of the floor assembly. Access is often possible from above (including inside the boot).	Dec21-28How12 12. Voids between the front outer bodywork and the radiator support panel are often encountered, and these can attract moisture. Comprehensive coating with wax/oil based fluid is advised here.
Dec21-28How13 13. Rust around the bonnet framework can be prevented by coating with protective fluid. In most cases you will be able to find access holes through which a flexible applicator tube can be introduced.	Dec21-28How14 14. Corrosion is often found around the outside edge of classic car boot lids, and this is usually caused by condensation within the reinforcing structure. Apply preservative fluid to keep it at bay.	Dec21-28How15 15. Excess fluid emerging from access and drain apertures can be wiped away with a soft cloth (which can be used to wipe over brake pipes etc.). Large amounts can be collected in tins for re-use.