Among all the email and other correspondence we receive at SILICON CHIP, there are many common requests which are quite understandable, especially as they tend to come from readers who are new to the magazine. But there are others which we find frustrating because they indicate that people are still being conned by peddlers of technical sounding rubbish. Under this heading come requests for us to do a project for electronic corrosion control for cars.

A recent email is typical. Here the person quotes from the glowing testimonial on a website and asks could we do something similar, especially as there does not appear to be much electronics involved. In general, the principle of all these schemes is as follows:

"A small pulsed DC power supply and control module about the size of a pack of cigarettes is the heart of our corrosion proofing systems. The power supply is all solid state circuitry embedded in electronics grade (UL 94V-0 flame retardant) epoxy encapsulant for long life and durability in any climate. On automobiles and light trucks it is typically installed in the engine bay or in the boot where it runs off the 12V from the vehicle battery, drawing less current than a typical digital clock.

One or more unique "programmed capacitive couplers" which are attached to the painted metal surface with aircraft-grade adhesive, are charged by the power supply/control module and function as if they were the positive half of a capacitor. They are wired to the power supply in parallel (each on individual circuits) and meticulously engineered so that each serves to produce a measured and specific limited range of capacitance and thus deliver a measured and specific limited range electrostatic charge via capacitive coupling. These capacitive couplers are vital to the effectiveness of the system and the utmost care is exercised in their manufacture".

Well, there you go. They must be good. Such systems frequently appear to be protected by a patent and they have all been endorsed by "university tests" or "independent engineers". Only the patent is never listed and details of the university or the "independent engineers" are never mentioned. Nor is there a warranty. Funny that.

I always reply to these emails along the lines that I regard electronic corrosion control as a lot of hogwash and a fraud. How can such a system possibly work? There is no current flow through to the car body and there is no sacrificial anode (and even if there was, it could not work unless the car body was immersed in water!).

Furthermore, if such a simple low-cost system was effective, why haven't the world's auto manufacturers all fitted it to their cars? The answer is that they don't work and present measures employed by most car manufacturers are so effective that they typically give a 6-year warranty against paint failure and perforation corrosion (or words to that effect). In fact, some new cars in the USA (where they put salt on the roads in winter) come with a 10-year warranty.

If you want further evidence of fraud, just log onto www.google.com and type in "RustEvader". This US company was prosecuted by the Federal Trade Commission as long ago as 1996 and prevented from promoting its electronic corrosion protection system. Yet many other companies continue to promote virtually identical systems. The message is simple. They don't work. They can't work. It's a con!

Leo Simpson