Rust - The Enemy of every Classic Car

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Not long after writing (yet another) article on the Gordon-Keeble GT (USA Edition), and not to be confused with the Gordon-Keeble GK1 AUS Edition review, we got to thinking about the enemy of every classic car owner - RUST. Despite the glassfibre body, even the Gordon Keeble contained a considerable quantity of iron-based metal, most of which had tendency to corrode.

There are some iron alloys, such as stainless steel, which do not corrode, but these, on the whole, are very expensive - too expensive for the motor industry then, and for the most part now. Unfortunately, it is not only iron which rusts: aluminium will soon be covered in a white coating of oxide if left out in the rain.

The main difference between this and iron rust is that, with aluminium, the coating stays firmly fixed to the surface, preventing any further corrosion, rather than flaking off and laying new metal bare to attack. Glassfibre cars such as the Gordon-Keeble GT were not immune to rusting, because they usually had a steel chassis to support the body. One of the drawbacks with glassfibre cars was that the metal parts tended to be forgotten, being hidden under a shiny and new-looking body many years after they rolled off the production line, which did not bode well for the classic car enthusiast. Although the chassis was always painted when new, it was soon susceptible to rust after that coating was chipped and scraped by flying stones.

In countries where rust was a real problem, tests were introduced to check chassis condition - something that is now commonplace. The British Ministry of Transport were amoung the first. No matter what the metal, rusting only occurs where the surface of that metal is exposed to the elements, particularly rain, which contains many elements and compounds.

Oxide and Hydroxide

The water will react with the iron or aluminium to form an oxide or hydroxide, which presents the characteristic brown or white coating. In the case of iron, once water finds a hole in a protective coating, such as paint, it will not be happy to create corrosion in that spot alone: the rust will quickly spread under the edges of the surrounding paint, which may eventually fall off in flakes.

The same problem does not arise with aluminium, because the corrosion does not creep more than a millimetre or so under the paint edges. Where two dissimilar metals are joined together, there is a strong tendency for rusting to set in; this is caused by an electrochemical reaction between the two metals, one of which is more electro-negative than the other. In this instance, the corrosion will not necessarily be due to the formation of oxide or hydroxide; it may comprise a compound of the two metals.

The most common site of this type of reaction is where bright-metal strips are affixed to the steel of a car body by metal clips. The cure, or more correctly the preventative treatment, is to fit plastic collars between the clips and the bodywork. The easiest way to deal with rust is always to put large obstacles in its way in order to prevent it happening. In other words, if the metal parts are given a thick and, more important, a complete coat of paint, then, as long as the paint is not chipped and scratched when assembling the components, rust is prevented from beginning its destructive process.

Paint technology has improved markedly in the last few decades, but chances are, if you are reading this article, you are a fellow car enthusiast and at least one of the cars that has secured a spot in your driveway is not of recent origin. The most important part of your classic car is the underside, since this is the area which is examined least often and is exposed to the worst wear and tear. Many cars built prior to the 1950's were not undersealed when new. Things changed in the 1960's and 1970's, many given a thick underbody coating of sealing compound; however, too much faith was placed in the glutinous substance, and the truth was it could never form a continuous layer unless applied before assembly of the parts.

Cars undergoing rust treatment

Inside of car showing surface rust

Rust on an Italin Car - Surprise!

Way Bad Rust

Looks impressive for the camera, but a pretty lousy job of rust prevention
Ask an automotive paint specialist and they will tell you that even the most powerful spray will not force the sealant to coat the top of an inaccessible chassis or subframe member. The main function of underseal, then, was to form a protective shield over the paintwork of the underside, in order to prevent flying stones from creating damage.

This function was particularly important in the wheel arches, where the tyres were continually throwing up stones and other assorted debris. The rules of car maintenance still apply today for your daily drive. In order to assist the paint and the under body coating in limiting corrosion, you have to clean the underside of your car from time to time - especially in the winter, and especially if you live in the Northern Hemisphere when the roads may have been coated with salt.

Accidental Mud Traps

Most cars, and particularly pre 1990 models, have mud traps unwittingly built into them somewhere in the region of the wheel arches. If wet mud is allowed to stay in these niches, it will make short work of a slightly imperfect paint finish. A hose and maybe a brush or soft scraper should be capable of removing the offending material. Unfortunately, the rust-proofing methods used by most of the car manufacturers were not very efficient.

After reading Weary Dunlop's War Diaries, we would not consider ourselves fans of the Japanese, however we can thank them for improving the technique and introducing lengthy body erosion guarantees. Perhaps this is because their earlier efforts were particularly susceptible to corrosion. And before anyone writes in to complain of our Japanese car bashing, the author owns 2 cars, both Japanese (and of course both rear wheel drive) - one from Aichi and the other from Hiroshima.

Although a vague effort was made from the 1950's onwards, in that a rust-inhibiting primer was used, it would not pay most of the builders to make cars last too long. One of the earliest aftermarket preventative rust-proofing treatments was "Protectol" - where two very different liquids were used, depending on the part of the car which is being treated. This process was based on the Swedish ML method of corrosion protection, pioneered in 1952 by Sven Lauren. A thin liquid, known as ML, was applied by an airless spraying technique to all the cavities of the car body. These included the doors, the door sills, the tubular or pressed-steel bonnet and boot struts and the door posts.

In addition to this, ML is used to protect parts where bright-metal trim is attached (this includes the badges). The nature of the ML liquid is such that it has high capillarity, enabling it to creep into welded seems and similar crevices. Holes are drilled in order to force the liquid into the 'sealed' cavities such as the doors and sills; these were plugged after the operation was finished.

The underbody was treated with Protectol VB, not the beer, but a thick compound, which was sprayed under extremely high pressure on to all body and chassis parts. Both this and the wax-based ML formed a flexible and self-healing layer, which would protect the metal for years beyond the manufacturers care.

The New Car Dilema

Lets face it, we all have faced the dilema when buying a new car as to why we need to pay more for the anti-corrosion treatment. On first take, we would (justifiably) assume their is collusion with the aftermarket companies who give generous kick-backs to the showroom. But, in our expreience at least, we can get the procedure if not thown in on the deal, at least heavily discounted.

But the question remains, why not do it during manufacture? Simply put, for a car manufacturer to incorporate this type of treatment into each new car, it would bring their production line to a snail's pace, putting the showroom sticker price up and ...ahem... whats the bet once you have decided on the car, the price is ALL that is now on your mind?

Once It Has Taken Hold, It Is Difficult To Stop

The question remains - do you need to fork out some extra hard-earned on any anti corrosion treatment? Difficult to answer, because there are so many variables, such as if you live close to the beach, or if you change your car over quickly. For the medium to long term purchaser, it is important to remember that once a piece of iron or steel begins to rust, it is very difficult to halt the process altogether; the only sure way is to remove all traces of corrosion by using an abrasive material. There is no point whatsoever in painting over the top of a rusty patch on a car body, as the corrosive action will continue under the new paint, which will soon flake off. And any sign of rust, and we do mean ANY, will seriously deflate your resale.

Can You Fix Rust?

Or, more to the point, can you be bothered? Once the metal has rusted extensively the surface will be badly pitted, so that treating it with a rust curer will leave it too rough for a smooth final paint finish. The answer here is to rub-down the damaged area, using wet-or-dry paper if it is a small patch or a rotary sanding disc on an electric drill if it is large.

The surrounding paint must be sanded until shiny metal is showing and the paint edges 'feathered' so that the repair will not be obvious when finished. Once the rust has been removed, primer must be applied to the bare metal to provide a key for the finishing coat, which should be sprayed on after the primer has been sanded smooth.

Of course, not only does rust spread if it is left untreated: it will penetrate deeper and deeper, as the flakes drop off, until a hole forms. In the motor car, most of the holes which are seen in the bodywork have been caused by rust starting, unnoticed on the back of a particular panel, such as a wing or a door. The first sign of this is when the paint begins to bubble for no apparent reason; a gentle prod at this stage with a sharp instrument such as a key or screwdriver will prompt the immediate formation of a hole.

Treating The "Rust Hole"

The treatment of a rust hole requires a different technique from that needed for a simple rusty patch. The metal surrounding the hole must be cut back, using a tool such as a pair of tin-snips, until all the rusty parts have been removed. If the hole is still only small, then body filler can be applied after gently hammering the edges of the hole inwards to form a dent onto which the filler can key. However, if the hole is large, then it will be necessary to place some support material behind the hole to prevent the filler falling in.

If the hole is a blind one, such as in a door or its sill, then the best material with which to provide support is chicken wire. This can be screwed up, forced into the hole and then allowed to expand against the edges. If the back of the hole is accessible, then a piece of perforated zinc sheet should be used; the edges of the hole should still be knocked inwards, but this time the back should be cleaned and the zinc stuck to those edges using body filler.

Whichever the case, once the support has been placed, body filler should be applied to it until the surface is level with the rest of the panel. When hard, this should be sanded down, using wet-or-dry paper on a block, until it is smooth. If necessary, further filler should be applied and the process repeated until there are no bumps or dips, and the filler edges are tapered onto the metal.

Priming and painting should then be carried out as before. Rust on a chassis member, or on any other important load-bearing structure, may necessitate the welding-on of a strengthening plate in order for the vehicle to pass roadworthy tests in your state or country.

The Shackles and Dampers

Sometimes such items as spring shackles and damper mountings are damaged by rust, and have to be replaced. Different makes of car have their own most commonly affected rust spots, but in general it is the door edges, the sills, the wings and the floors which rust first-all places which come regularly into contact with water. Obviously there are exceptions, such as Italian cars of the 1970's - brilliant in many respects, but the "commonly affected" rust areas pretty much are all inclusive - even the ignition keys.

Accident damage, even though repaired, can give rust a useful opening; it is easy for a repair shop to make the exterior surface perfect, without remembering that the inside may well have lost its paint. It is a good idea to check any body repairs and, if possible, to apply a solid coating of underseal to any repaired or replaced panels.

Welded seams are the most important areas of all, because any rust which starts here will soon penetrate to the other side of the seam, which may well be on the outside of the car. Finally, if your classic's chrome-plated parts begin to rust, there is little that can be done, short of stripping off the plating, making the metal good and starting again with a new chrome surface.

This may be worthwhile for an obsolete car whose spares are not available, but it would be expensive, so if you can find a supplier of quality reproduction brightwork and bumpers, it will save you a bundle. And best still, last time we looked, there was such a supplier listing their products in the Unique Cars and Parts Classifieds. And if you think you can help your fellow Classic Car enthusiast, why not leave some tips in the Reader Reviews section below?

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