Search For Solution To Rust Problem

Press, Volume CIX, Issue 32076, 26 August 1969, Page 13

Search For Solution To Rust Problem

<By

FRANCIS COOPER)

For fourteen years two steel rods stood immersed in small troughs in the corner of a United States technical laboratory. Recently’, when they were removed and examined, one was found to have been almost eaten through by rust.

The other was as smooth and shiny as the day it had been put in. The secret—which concerns every man who has ever worried over the spots of rust appearing along the bottom of his car—was in the solution in which the steel had been standing. Recently, a natural gas i pipeline burst near Paris,! killing a score of people in

nearby houses.... Explosions levelled a West German chemical plant, killing 20 and I injuring many more. Io both cases, safety experts have been able to piece together the tell-tale clues that expose rust as a killer. Rust also hits hard on the purse. Last year, for instance, we paid an estimated £4OO million to replace or repair (rotted car panels, ruined tools, disabled machinery.

damaged buildings, as well as for protective paints, and coatings and for further corrosion research.

The crumbling red rust on iron, the powdery white deposits on aluminium, the bluegreen verdigris on copper, the black tarnish on silver—all are examples of corrosion—now one of industry’s major enemies.

But it has not been until recently that an army of cor-

rosion engineers—chemists, metallurgists, and physicists from nearly every industryhave been mobilised for a full scale attack. Few details of its make-up have yet been released, but it is known to contain technetium, a mildly radio-active man-made element which is a by-product in the manufacture of nuclear fuels.

This apparently provides metal with a surfacing so tough that corrosion can’t get a foothold. Once this coating can be produced on a commercial basis cars should—technically—last at least twice as long. End Of The Road “In today’s no-chassis car, the engine is often the last thing to wear out,” says a car research engineer. “Once the body work begins to rust in vital places—round the springs for example—it is usually the end of the road for the car.” i In fact, where ever metal is used, rust is winning -an increasing number of victories. I “The trouble is,” one expert explains, “that metals don’t like being metals. They’d rather combine with oxygen and other elements and change back into impure forms much like the natural ores from which they were refined.” Rust fighters are now trying to stop or, at least slow down the process with several weapons. One of the simplest and most effective is a coating of protective material, applied as a liquid, that either seals the metal from moisture or chemically slows the corrosive process. Thin Coat Special formulations are now available for application over steel, and other metals,

and industry also uses a variety of organic and inorganic protective coatings, including coal tar, plastics and porcelain. Electroplating often helps too. A thin layer of chromium or other resistant metal protects the metal underneath and provides an attractive finish. All metals corrode, but some corrode quicker than others. Aluminium and lead for example, quickly form a thin, protective coat of corrosion that doesn’t spread deeper. Modem metallurgy has developed many sophisticated alloys combinations of metals—that offer corrosion resistance along with other desirable qualities, but all these are expensive. Steel is often essential for many jobs, but this can be treated with a “weathering process” which causes it to grow a multi-tone brown skin. Much Faster This skin actually is a coat of rust so tight and closegrained, that it protects the metal underneath.' Yet another way of thwarting corrosion now being tried, is to design the trouble spots out of metal objects. New car designers try to avoid pockets, ledges, and other irregularities. Corrosion engineers also know that when two different metals come into contact, the more electrochemically active metal corrodes much faster than the other one. For instance, stainless steel tableware will eventually become pitted if It’s left in contact with silverware. Therefore, if? two metals must be used / together, engineers must try to insulate them from each other. Best Weapons This strange ability of one metal to speed up the destruction of another, also has its uses. By sacrificing a small amount of expendable metal, engineers have found they can protect vital metal structures from corrosion. This principle is especially useful in ocean-going ships, which are subjected to highly corrosive salt water. By studding the hull with bars of “sacrificial” metal, engineers have found they can cut down corrosion enormously. Eventually, it is expected, all these developments will come into general use. Until then, a wire brush and a tin of lead primer are ’still about our best weapons in the fight to keep the rust away from our cars.—Copyright, Provincial Press Features.