TORONTO, Ont. –As fleets aim to extend equipment life in the face of increasingly challenging operating conditions, one place they may want to direct their attention is to the prevention of trailer corrosion.

A trailer is a significant investment, yet each year many of them find their way to the scrap heap early because they were improperly spec’d and poorly maintained. Corrosion is a formidable foe, even for the best built trailers. However, customers have several weapons in their arsenal that can be used to limit -if not defeat -corrosion.

Darry Stuart, founder of DWS Fleet Management and the former chair of the Technology and Maintenance Council (TMC) spearheaded a TMC study group on corrosion about 10 years ago. While the materials and techniques used by trailer manufacturers have evolved since then, so too have the de-icing agents used on the roads.

The killer chemicals used on Canadian highways include: sodium chloride; calcium chloride; and now the most harmful of them all -magnesium chloride, which is spread on the road even before a snowfall to prevent accumulation.

“Magnesium chloride is probably the best one for keeping cities’ budgets down, but the worst one for corrosion,” notes Ray Camball, fleet sales manager with Trailmobile Canada. As a result, Stuart predicts corrosion “is going to be one of our toughest things to deal with over the next 15-20 years.”

What causes corrosion?

Corrosion results from a battery-like interaction between two metals where an electrolyte -with a voracious appetite for metal -and oxygen are present.

The electrolyte is fueled by chemicals (such as those found in road deicers) and moisture, of which there’s an abundance in Canada.

Areas of the trailer where two different types of metal are within two inches of each other are especially vulnerable, explains Camball, who is also a mechanical engineer.

“I’d be suspicious anytime two metals are getting together,” he explains. “If a brass connector for a light screws onto aluminum, you’ve got different metals and salt is eventually going to cause a problem.”

The relationship between various metals is a complex science. Each metal has a different voltage level, which determines its susceptibility to corrosion.

In some cases, even the same metal carries different voltages. The area under a rivet, for instance, often corrodes first because of its lower voltage, explains Camball.

Trailer manufacturers have attempted to use the voltage variances in their favour, by using low-voltage metals as a shield to protect more vulnerable types of metal such as aluminum or steel. Most notably, this has been achieved over the past several years through the galvanization of components such as door frames.

The components are “hot-dipped” into molten zinc, which forms a protective layer on top of the metal, explains Camball. Galvanized trailer parts have been on the market for several years here in Canada, and have held up well to winter conditions.

“It’s the most effective way of combating corrosion,” insists Camball.

Parts that are most commonly galvanized include: door frames; landing gear; cross-members; corner protectors; and even wheels. There are even some fully-galvanized trailers and container chassis on the market, in Canada most notably produced by Di-Mond Trailers.

Alternatively, some manufacturers have used coatings that are designed to prevent moisture and chemicals from contacting the metal in the first place, but they’ve met with mixed results.

“I’ve seen the results of strong epoxy coatings tried in the mid- 1990s that caused more corrosion than having unpainted steel, because they trapped saltwater (underneath) allowing the steel to fester 24 hours every day rather than just when it was wet outside,” says Camball.

Stuart also recalls peeling large sheets of metal right off the cross-members, although he feels the poor metal quality was as much to blame as the coatings.

“There was a period of time when cross-members literally rotted right out of the trailers,” he says.

Trailer manufacturers continue to experiment with coatings and most recently Great Dane launched its CorroGuard “spray-in- place thermoplastic elastomer coating,” which the company claims is basically impenetrable to moisture and chemicals.

Inspect the trailer

Regardless of whether you choose to protect your trailer using galvanized components or a new generation coating, there are other ways you can extend the life of your equipment. For starters, it’s a good idea to inspect the entire trailer, looking for pockets where water and road salt can become trapped.

“Those aren’t so obvious sometimes,” points out Camball. “Try to totally fill the gaps so there’s no air void, or at least have a way for water to drain out.”

That may mean caulking the top of a cavity and leaving the bottom open so water can easily escape. Customers should also be mindful of the effects of combining two types of different metals. Stainless steel door-frames certainly look nice, but if they’re adjacent to a lower-voltage metal such as aluminum, corrosion will simply attack the more vulnerable metal.

“The problem with stainless steel is that it causes things nearby to corrode,” notes Camball. “It’s a mistake to spend the extra money on a stainless steel doorframe if it’s next to an aluminum skin.”

Washing trailers to remove corrosive materials is another tactic that can prolong equipment life – to some extent.

“I think washing of vehicles is going to be more important than it’s ever been,” Stuart says. “I don’t think washing is going to stop anything, I just think it slows it down.”

Great Dane recommends frequently cleaning trailers using a “properly mixed ration of soap and fresh water,” in any weather.

But Camball cautions that washing trailers with chemical ‘brighteners’ may do more harm than good, especially to galvanized parts. Using too much brightener can remove the protective outer layer of zinc, exposing the steel to electrolytes.

“Some people that mean well and do a lot of cleaning of their vehicles will put brightener into the water, and that makes the trailer look beautiful but (the chemical) becomes an electrolyte and if you don’t get it washed off all the way, it gets driven into the crevices and now you’ve created another problem,” he warns.

There’s also the risk that high-pressure washers can drive existing road salt and other contaminants deeper into crevices and perforations where they’ll remain to fester.

“Just having rain washing a trailer is a method that has been proven to work well in many fleets,” points out Camball.

What to look for

Mechanics and drivers should keep an eye out for bubbling paint, which may indicate corrosion is occurring beneath the surface. “Anything that’s starting to swell means something is trapped underneath there,” Camball says.

The wood inside trailer doors may rot away if moisture seeps in through bolt-holes and fasteners, however newer composite doors are less susceptible to this problem. Underneath the trailer, ensure drain holes aren’t plugged and that moisture and road salt has an escape. If square tubing is used for the cross-members, ensure there are drain holes so that water doesn’t get trapped inside. Inside the trailer, Camball says there should also be an escape hatch for spilled liquids or moisture that forms from condensation.

If a spill does occur inside the trailer, cleaners should have access to wide-range litmus strips, so they can determine if the material is “alkaline or acidic,” suggests Camball. Otherwise, a seemingly harmless spill can be the beginning of a long-term battle against corrosion. Even some absorbent materials are alkaline themselves, Camball notes, leaving a corrosive residue to eat away at aluminum over time.

When spec’ing a trailer, Stuart says it’s important to prioritize which options will play the biggest role in extending trail
er life. You’ll never eliminate corrosion completely, he admits, but you can get the upper hand on it and prolong the life expectancy of your asset.

“If you put in $1,000-$2,000 to prevent corrosion, you’ve got to extend the life of that trailer,” he says.

There are some options he considers vital.

“I would not buy a trailer today without stainless steel parts, I would not buy a trailer without coated cross-members and I would not buy a trailer without extra cross-members,” he says, noting additional cross-members may be as effective as some of the more costly anti-corrosion options.

Camball says upgrading to a 3/8-inch thick coupler plate is another cost-effective spec’ that can extend trailer life.

“The coupler plate is a key structural component that is subject to a build-up of salt inside cavities and they tend to get thinner with age, especially in years 10 to 20 of operation in Ontario and other areas of the rust belt,” he reasons.

A 3/8-inch coupler plate can be spec’d for about $100 whereas repairing a thinner plate can cost as much as $2,000.

“Even though the rust inside a coupler cannot be seen, it’s comforting to know for safety reasons that the coupler is strong – especially when hauling heavy or high-swaying loads,” he explains.

The battle against corrosion is far from over. But advances in trailer design combined with proper maintenance can at least stem the tide and add years to the life to your equipment.