Can corrosion ever be completely prevented or eliminated? That's the question we posed to technical experts recently, in the hopes that they might offer some hope in the endless fight against rust. Alas, they couldn't promise that rust will ever go away, but they did offer some helpful information that could add life to your fleet vehicles.
"The best way to prevent corrosion is to be proactive," says Dan Williams, technical sales manager of Eureka Chemical Company, makers of Fluid Film coatings. "Preventative maintenance is much more cost-effective than dealing with corrosion after the fact. Regular washings and keeping a car dry are important maintenance practices, as are proper storage of vehicles when not in use and the use of an undercoating and corrosion preventive."
John Lewis, brand manager for commercial transportation coatings for PPG, says, "Corrosion will always be there. We do the best we can to try to slow down corrosion, whether it be by pre-treating the metal or putting a coating or physical barrier between dissimilar metals, but it is an ongoing chemical process; if you have oxygen and water and dissimilar metals touching, you will begin the corrosion process."
The sad truth is that many fleet vehicles operate in conditions and applications that promote corrosion.
"Environment is a big factor for corrosion issues," Williams says. "The worst areas for vehicle corrosion are areas of high moisture such as marine environments or areas of heavy rain or snow melt off."
"Vehicles that are on the road more in harsh environments--where there is more chipping and cracking and damage to the coatings themselves, that opens up sites of corrosion more readily," says Lewis. "If the vehicles are routinely rinsed down, washing the material off is a good way to prevent the chemical cycle from continuing."
"What we see with ambulances, say, in Chicago, that are literally out on the street 24 hours a day, they don't get washed like a fire truck that goes out to a fire, comes back and gets washed, rinsed, polished, buffed--those are the two duty-cycle extremes that you'll see with work vehicles," he says.
"What has really exacerbated the problem is the growing use of magnesium chloride by municipalities," Lewis goes on. "It is cheaper to use, but it is reportedly many times more aggressive in terms of corrosion. What makes it potentially worse is the presence of a ‘stick-um,' a resinous material that helps it stick to the road, and creates a greater potential for corrosion. It can get up inside vehicles and if experiences moisture it will continue to corrode."
Unfortunately, that advice about frequent vehicle washes may not hold water where magnesium chloride is concerned, because it may come to rest in areas of the vehicle that are inaccessible to the wash.
Keeping vehicles corrosion-free would be a lot easier if the vehicles never came into contact with the ground. That, of course, is where all the trouble starts.
The parts of a vehicle that are closest to the ground--brakes, axles, brake lines-- are the ones at greatest risk of corrosion, but Lewis suggests that technicians look beyond the obvious.
"You also need to consider the structural integrity of the vehicle," he says. "The structural part of the underside of the vehicle, since it's mostly going to be chipped and abraded by rocks and sand, is going to corrode over time. Although it may not be as dramatic as a brake system part failing, certainly it's something that is very important in terms of maintenance and checking."
Here's PPG's list of the most vulnerable structural materials:
• Anything made out of cold-rolled steel
• Anything made of iron
• Anything made with a bimetallic configuration, such as stainless steel to aluminum, or stainless steel to cold-rolled steel
Beyond that, galvanized steels are better than non-galvanized steels at resisting corrosion, and aluminum is even better than galvanized steels.