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Rustproof for longer life

September 7, 2011 at 12:36 pm
filed under Rust
Tagged Automobile, Drill, Paint, Rust, Shopping, Wire brush

Rust is the biggest single cause of a car’s deteriorating. It attacks two main areas – the lower parts of the body, which are subject to the impact of stones and grit, and the inner skins of the structural box-sections, into which water finds its way through tiny joints not fully closed in manufacturing. In addition, any rust which has settled on a sheet of steel in the factory will keep on spreading until its progress is stopped.

A rust-prevention treatment is ideally suited to a new car where, hopefully, rust has not had a chance to get far. Older cars can also be treated, but only formation of further rust can be prevented. Rustproofing will not clear up existing rust damage.

Rustproofing involves scraping all the mud and dirt that has collected on the underside of the car, brushing off any flaking rust and applying one or more coats of an underbody protection material. The process also includes spraying inside the sills and box sections with a rust-preventive fluid.

This is a long and messy job. Its main benefit is that the rust will be virtually banished for years. It is also likely that noise inside the car will be less, and that the car will fetch a higher trade-in-price.

Removing the mud

The easy way of removing the dirt from underneath is to take the car to a specialist garage with a steam-cleaning service. High-pressure steam blasts all the mud from the underside of the car and also removes any oil and grease.

To clean the underneath of the car yourself, you will need some scrapers and a wire brush. You will also need a hose and some old clothes, preferably a set of overalls. Wearing a balaclava helmet and a face mask is a good idea.

In order to make a thorough job, the car will have to be jacked up fairly high. So for safety’s sake it will be worthwhile to hire a trolley jack and axle stands.

With the car jacked up and the axle stands in position, remove the road wheels. This makes it easier to reach the wheel arches. To ensure that the brakes are not contaminated by the rust preventative, tie a polythene bag over the brake assembly and steering joints.

Dry dirt can easily be removed, but the lack of water will produce clouds of dust. So thoroughly, wet the underside of the car so that all the dirt is sodden and can be prodded away with a scraper. Most of the dirt will fall away fairly easily, but a wire brush will probably be needed to shift mud away from odd crevices. Every bit of dirt should be removed, or the action of the rust preventative will be spoilt.

Patches of oil and grease will call for special attention with a detergent or degreaser, and any flakes of peeling paint or rust must be wire-brushed away. Do not use an electric drill with a wire-brush attachment; apart from being too harsh, it tends to shower you with dirt.

Heavily-rusted areas should be thoroughly scraped and then a rust killer applied.

Brush-applied sealant

One type of diy underside sealant takes the form of a ‘paint’ which is applied with a brush. Such paints usually have a bitumen/rubber base which withstands physical impacts from stones and grit as well as providing a water-repellent layer.

Sprayed-on sealant

The alternative to the paint is a wax-based spray such as Rustex. Good kits of this type include a special hand-operated spray gun, a gallon of sealant for inside the doors and box sections, a gallon of underbody protector, a spray gun, various lances and an instruction manual. There are also plugs to block up the holes through which the material is sprayed.

The process is much the same as with a brush-on sealant, except that the job is usually a little easier because it is possible to work a short distance away from the area of metal being covered, thus avoiding the chance of the protective material falling on to one’s face.

Using the sealant

The material – spray or brush – is best applied in a fairly thin coat followed by a second, and even a third, coat when the first has dried. As a fairly thin coat dries out quite quickly, the first half of the car is usually ready for the second coat by the time the other half has been completed.

When applying the material, avoid the handbrake cables, adjuster points, grease nipples and other items that demand periodic attention. The best method of protection is to tape them securely with masking tape. Metal brake pipes can safely be treated, but keep the material away from the propeller shaft.

Pay special attention to the jacking points and sub-frames bolted to the main bodywork. Work the brush or spray along these joints with plenty of compound, but try not to block up any drain holes.

‘Mud trap’ areas – under the front wings and other places – will have become obvious when the car was being cleaned. Wheel arches, where abrasion is a problem, can benefit from extra layers of the material. When the job is completed, it is a good idea to use in these places any sealant left over.

Some cars may have deflector plates fitted to keep the worst of the mud away. If these plates can be easily removed, do so and work behind them. Otherwise, treat the plates themselves and work the rust-preventative behind them.

Treating the exhaust is a waste of time since the compound rapidly burns off. Similarly, electrical connections should not be treated in case the material works between the connections to form an insulating barrier. But on old cars whose battery carrier is underneath, it is well worth treating the carrier thoroughly, as it is subjected to attacks from road-borne contaminations as well as any leakages of acid from the battery.

Keep the material away from leaf springs and moving parts of the suspension. Avoid also the breather holes around the back axle.

Where the bodywork is concealed by the bumpers, the material can be extended slightly up the outside of the car on top of the paint, to offer protection against stones and grit. A strip of masking tape along the sills will allow the sealant to be applied to the outside of the car along its lower edges, where it cannot be easily seen. This extra work is well worthwhile because it is the lowest parts of the car that are most prone to corrosion.

The materials used for underbody protection are safe enough to use, but care should be taken to avoid inhaling any fumes. Keep the material away from naked lights. Odd drips of the material finding their way on to the paintwork can be removed, while they are still damp, with a rag dipped in turps, substitute or whatever other solvent is suggested on the container.

Inside the box panels

The box panels call for more specialized treatment. The idea is to put two or three layers of rust preventative material all round the insides of box panels in order to provide a barrier against moisture. In some cases, new cars may have ‘had their sills already treated by the manufacturers, but no harm is done by adding further protection.

Start with the inner sills. In many cases, removing the carpets will reveal holes suitable for inserting the nozzle of the probe supplied. If there are no such holes, a 6 mm drill will make a row of openings, say, two or three per sill.

Feed the probe into the sill until it can be felt to have reached the end. Pump the spray gun to start the liquid flowing and as the pumping continues, bring the probe slowly back towards the hole. The liquid will flow all around the sill interior and find its own way into odd corners. By the time the second sill has been treated, the first will be ready for a second application.

The outer sills may have drain holes in them already. If this is the case check that the drain holes are free and not choked with mud. Apply the material in the same manner as before.

Cross-members supporting the steering and rear suspension assemblies can easily be reached from inside the car by drilling through the floor. Drill a hole in each section to insert the probe and follow the same routine.

Structural sections that brace the floor can be found by looking for twin rows of weld marks, which show up as small dents in the floor. A hole can be drilled anywhere between a pair of such lines to allow the probe to enter. If the location of the sections cannot be found from inside the car, it will be necessary to go underneath and drill through the sections themselves.

The bottom parts of doors tend not to be as vulnerable as they were a few years ago, but nevertheless they should still be treated. Drain holes are usually found under the doors and these holes make good probe-holes. Otherwise a 6 mm hole will be needed.

Slide the probe upwards until it is balked by the window winder gear; this is high enough to protect the interior of the door. It may be necessary to treat the doors from both front and rear edges to make sure the entire area is covered. This is especially true of two-door cars, where the doors are larger than those on four-door models.

While you are working in the door area, the door surrounds ought to be treated. Courtesy light switches can usually be pulled out to allow entry to the surrounds; otherwise a hole can be drilled at any convenient spot.

The areas in front of and behind the front wheels are established ‘mud-traps’ calling for treatment.

Access to the panel between the windscreen and back of the front wheels is gained from underneath the carpets inside the car. Here it is a good idea to lay on three or four coats of rust preventative.

Many cars show signs of serious corrosion around bracing struts supporting the bonnet and boot lids. With the bonnet and boot raised, drill holes at the top of the bracing struts, push the probe down to the bottom and apply the sealer in the usual way. If traces of liquid appear from under the braces, they can safely be left as they will harden off in a short time. Alternatively, they can be removed easily with a rag moistened with white spirits.

By the time the box sections have been treated, the underside of the car will be dry. Odd traces of fluid from both operations may appear at first, but again they can be removed with white spirits and a rag.

There may be some slight smells from the car as any sealer that has fallen on the exhaust is burned off. This will pass within a day or less.

The underside of the car should be checked once a year in case any parts of the sealer have worked loose.

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