Controlling Tin Worms or How to Keep Your Coaster From Rusting -

Rusting causes steel to become porous, bulkier, weaker, and more brittle. It is not a disease, just an unwanted example of the way that energy becomes increasingly disordered (i.e. it’s entropy in action). Unless protected as well as the Sydney Harbour Bridge, most things made of steel eventually rust - motorhomes not excepted. Rusting starts when bare steel is exposed to water, or a damp atmosphere. Oxygen then combines with the steel’s iron, forming a solution of dissolved iron that filches electrons from the steel. The associated flow of electrons allows oxygen atoms to bond with the steel, converting it into rust (ferric oxide). Rusting continues unless electron flow is somehow halted. Ways of limiting rusting include alloying steel with chromium or chromium-nickel (stainless steel) to make it substantially inert. It can be coated with zinc (galvanising): the zinc sacrifices itself for the presumed better cause. Chrome and other plating protects against rust, but imperfect chrome plating speeds it up!

Steel can also be coated with wax, fish oil, enamel, epoxy paint etc, but rusting will begin where gaps, pits, or scratches expose bare metal. Steel-hulled boats are protected by sacrificial zinc anodes, but anodes, and the metal bits to be protected, must be in a conductive liquid such as seawater. This is only marginally useful if you’ve sunk your Coaster on Fraser Island. Impressed electron protection is a proven alternative to rust reduction (but not elimination) and has successfully protected pipelines for decades. Until recently though its application to cars and trucks has been unfortunate. Not that it didn’t work - but it was bedeviled by hype that caused buyers to expect results more probable from Lourdes than Los Angeles. But despite the appalling publicity (from the industry’s point of view) many people with impeccable credentials had reported that impressed electron technology reduces corrosion in cars. Fortunately the industry regained respectability following a major Federal Trade Commission action in the USA in 1996.

How it Works

The technique works by impressing a controlled, pulsed current onto a vehicle’s chassis and body, the electron flow (that causes our metallurgical misery) is substantially nullified. It will not totally eliminate rusting nor reverse it. Australian manufacturer, Raider Electronics, says ‘it is not a miracle cure . . .’ [but] ‘it typically retards rusting by a factor of four to five’. These results were verified by Donald Harrison, CBE, DFH, C.Eng,MIEE (who concluded that it was a most effective method of rust protection, and by ETRS (Henderson W.A.) with the tests refereed by Dr. Robert Francis of the Australian Corrosion Protection Centre (part of the CSIRO). Using a Raider unit (supplied by Endrust Australia) I have been testing the technology on my OKA for three years. I have steel test strips, identically primed and coated with an epoxy primer - and identically scratched down to bare metal. Two strips are protected. A non-protected strip is used for comparison. There are also a few small body areas where deep scratches penetrate to base metal. The OKA has subsequently travelled over 60,000 km, including three months to the very tip of Cape York, innumerable overnights also close to the sea. The vehicle has been left in the open, within 300 metres of the sea, since April last year whilst building our new house north of Broome.

It Seems to Work

The unprotected strip became heavily rusted after two/three months. It is now deeply pitted. The protected strips remained rust-free for about three months then progressively acquired a soft light-brown powderish coating that readily wipes off with a paper tissue - exposing clean, shiny metal. Untouched, the coating remains soft and does not appear to build up further. The small areas of bare metal on the body also acquired this soft coating. Whilst I cannot endorse the claim that rusting is ‘retarded by a factor of four to five’, but it clearly is being retarded. Where ‘rusting’ occurs, it seems to form an apparently protective coating, which if removed, discloses cleanish, shiny metal. A curious bonus, observed also by other users, is that paint work acquires and retains a ‘bloom’. Whilst I’m mainly familiar with the Raider/Endrust unit, the technology is largely in the public domain, and most vendors’ units seem generally similar in design and construction. Cost is around $400 - $500.