LJK Setright: All that glisters: decoration to deceive the eye

Shiny metal has always been popular for highlighting the shapes, and distracting our eyes from the uglier features, of our cars.

Shiny metal has always been popular for highlighting the shapes, and distracting our eyes from the uglier features, of our cars. At first it was brass, then nickel, with occasional silver for the truly aristocratic. Today a microscopic layer of aluminium between layers of plastic performs the same duties and needs no polishing. Between these extremes there was always chromium, and it is still around, though more likely to be seen inside the cabin than outside.

Adding chromium has long been a traditional method of adding marketing appeal to a car that needs a face-lift. The surprise is not how much it has been used, but that chromium plating only became commercially available 80 years ago.

A French chemist, Louis Nicolas Vauquelin, had discovered chromium in 1798. Within 60 years, another, H E Sainte-Claire Deville, had produced it in its metallic form. Before another 60 years could pass, the exigencies of the First World War saw chromium used for coating projectiles (in hardness it ranked nine on Moh's Scale, level with rubies but below diamonds at 10). And when the time came to turn swords into ploughshares, there was uncovered a huge market for this brilliant material, which when electroplated reflects white light to about 77 per cent.

Soon, the formerly workaday American car carried chromium plating, making it something to be pursued for its beauty as well as its utility. Soon afterwards, the same began to happen in Europe, where the traditional nickel-plated decorations (which needed polishing, if not as frequently as silver or "German silver'' - a copper, zinc and nickel alloy popular with the bourgeois) soon took on the distinctive brilliance of polished chromium.

When the job was done properly, nickel was still there. Chromium plating is porous, and applying it directly to base metal allows substances to penetrate and set up corrosion underneath. Nickel plating is not porous, so it was best retained as a supporting layer, and to ensure really good adhesion it was advisable to begin with a layer of electroplated copper. Done properly, then, the process was not cheap, but doing things properly seldom is.

It was only in the years of austerity after the Second World War that the perils of doing it cheaply began to show. British cars, in particular, suffered: nickel was scarce, and in many cases chromium plating was applied direct to decorative mouldings that were porous, zinc-based die-castings. Before long the plating would show lots of bubbles, and before much longer it would begin to peel away.

Worse was to come. The US industry's lavish use of chromium plating to decorate cars in the 1940s was merely vulgar. But it became tasteless and ignorant when the restorers of vintage cars began to use it everywhere possible on their precious vehicles, even though it was anachronistic. And when they started chromium plating the spokes of wire wheels, that was dangerous!

The secret of the seemingly flimsy wire wheel is that all its spokes are in tension. Electroplating steel spokes puts a compressive stress into their surface, dangerously shortening their fatigue life. No self-respecting scrutineer at a race meet would allow a car with plated wire wheels out on to the track, but people continued to demand them. On the whole, it was one more reason why the wire-spoked wheel has disappeared from modern cars.

To this day, aesthetes and engineers deplore the careless or improper use of chromium plating on cars, however great its appeal. Perhaps the most succinct comment was made in the late 1920s, when Rolls-Royce was beginning to use chromium. The distinguished Frenchman Gabriel Voisin, who always yearned that the cars he made be beyond reproach, declared that he would not use chromium plating until Cartier sold artificial pearls. Give a thought for poor Voisin now. Today it is likely that your car displays artificial chromium plating.

motoring@independent.co.uk