By Jim Kerr
Rust. It’s a small word that can cause so much grief. Rusted bolts on a vehicle can make them difficult to repair, which adds to the cost of any repair work. Rusted sheet metal looks unsightly and devalues the vehicle. Let the rust get out of hand, and body panels can become rusted completely through, possibly causing structural failures or allowing exhaust fumes into the passenger compartment. This is extremely hazardous and in most areas of the country, can cause the vehicle to be certified unsafe to be driven. The hard-earned money you spent on that automobile just became almost worthless. So how do we prevent our vehicles from rusting?
Automobile manufacturers have been helping. Almost all metal body panels with the exception of roof panels on newer vehicles are galvanized. This zinc coating helps protect the metal from rusting, although it won’t totally prevent it. Exterior trim and badges are often glued to the body rather than bolted in place so there are no holes in the body with chipped
paint edges to allow rust to start. More durable seam sealers are used during assembly, and most vehicle manufacturers use electrostatic charges to attract primer paints into difficult to access body areas so that the complete body receives a protective coating during the assembly process. Even with all this attention to preventing rust, mother nature still takes her toll and you see rusty vehicles on the road.
Rust is a chemical reaction between iron molecules in the steel panels and oxygen. Add some moisture and/or heat and the chemical reaction occurs much faster. During the rusting process, a very small electrical current is generated, similar to the chemical reaction that takes place inside a battery, but with a much smaller charge. Hook up a sensitive voltmeter to a rusting panel in contact with salt water (salt accelerates the rusting process) and you can actually see the electrical potential generated.
Coating the body so that oxygen and moisture can’t get at the metal is one method of reducing rusting – that’s what paint, undercoatings and waxy rust prevention coatings do, but coatings aren’t perfect. Scratches or stone chips in any coating will expose the metal. Rust occurs at the molecular level, so even the smallest mark can let rust start and it will continue to grow under the coating. I have seen large chunks of paint fall off badly rusted cars, where the paint looked pretty good but the metal was eaten almost entirely away.
Another way of reducing rust is to fight it electrically. Remember how rust creates electrical power? What if we could reverse the power? That’s the concept behind electronic rust prevention systems. This system uses capacitance by attaching plates to the body to create a negative charge on the vehicle’s body. The negative charge counteracts the electrical charge of the rusting action, slowing rust formation.
Other systems use cathodic protection, which is the real name of the technique these companies are trying to sell. This method of using a sacrificial cathode has been used with success to protect against corrosion on many structures and systems including sea-going ships, buried pipelines, and even reinforced concrete. The system produces a reverse charge in the component or structure to slow or prevent the rust action from taking place on the body and use up the cathode material instead. There’s a catch however.
To create an electrical current, there must be a complete electrical circuit. In boats, the water forms one part of the circuit. In buildings, the ground forms one part of the circuit. Cars however, are not immersed in water or buried in the ground. If there was a good
return path through water or dirt, this concept might work, but it doesn’t have one. Another problem is that to create a charge over the complete vehicle body, the electronic rust prevention systems would have to use enough electricity from the vehicle’s battery that it would keep draining the battery so your vehicle wouldn’t start.
Would I recommend electronic rust prevention? No. I would save my money and apply it to keeping the vehicle clean. Rust occurs mostly where dirt and debris collect in recesses in the vehicle body. This area dries out slowly, so rust has a prime environment to occur. Wash under the vehicle thoroughly, inside front fenders and along trim to flush dirt out of corners. A clean vehicle dries quicker and dry vehicles rust very slowly.