November 1, 2015 4:15 AM, EST

Wheel Makers Use Coatings in Battle Against Corrosion

TT File Photo
This story appears in the Nov. 2 print edition of Transport Topics.

A tiny rock, de-icing material or salt and sand can start the process of turning a perfectly good wheel into a rust-covered embarrassment or, worse, a safety hazard. To prevent that from happening, motor carriers are using effective maintenance techniques, while manufacturers are producing more corrosion-resistant wheels.

De-icing materials, such as magnesium chloride, are more effective than traditional salt and sand at keeping the roadways safe because they prevent icing in the first place, said Robert Braswell, technical director for American Trucking Associations’ Technology & Maintenance Council. But they come at a cost.

Because those materials adhere to surfaces, they create extra corrosion of wheels, wheel fasteners, brakes, frames and other metal components.

TMC has shared its expectation with manufacturers and SAE International, formerly the Society of Automotive Engineers, that a heavy-duty truck should stay in service for eight years without a failure due to corrosion.

But reaching that goal requires participation from motor carriers themselves.

Braswell said fleets must find the right wheels for their lanes and then maintain them properly through a process of cleaning and lubricating that TMC has outlined. One tip: Make sure an automatic washer’s water is filtered so the de-icing material isn’t simply being washed back onto the wheels and other components.

“It basically comes down to spec’ing and maintenance, and it’s not easy, and it needs to be conscientious — kind of like taking care of your teeth,” Braswell said.

The most important question fleets must ask during the spec’ing process is this: steel wheels, aluminum alloy or both? Steel is stronger and cheaper, but aluminum corrodes less.

Accuride, which manufactures both steel and aluminum wheels, touts its Steel Armor product, which it introduced in 2013 and now uses on all its steel products. The technology uses a three-step process to prevent corrosion from spreading: a zinc phosphate that prepares the metal for adhesion, an epoxy electrocoat with a special formulation to protect edges so rust won’t spread and a powder top coat.

According to Craig Kessler, vice president of engineering, and Rafael Gonzalez, director of product management for wheels, the design prevents corrosion from spreading. In previous applications, damage to the paint by a rock or other object more easily opened a path for rust to spread under the paint. Steel Armor is designed to stop that spreading process where it starts.

The company says the technology adds 24 months before refinishing is required, adding 200,000 miles of service.

Maxion Wheels uses a similar three-layer process through its MaxCoat coatings system, said Mark Fonte, marketing and sales manager-OE truck and military. That process includes a primary layer of zinc phosphate for pre-treatment. Atop that layer is an epoxy primer that is then covered by a topcoat layer of paint.

What happens when steel wheels do become corroded? Fonte said they must be stripped of all remaining paint and corrosion and totally cleaned to ensure the new finish adheres properly. Once that happens, the three-layer coating finish can be reapplied.

What’s ahead? Fonte said manufacturers are developing harder after-cure paint surfaces and coatings to better protect against nicking and ultraviolet rays. “There are also an assortment of different coatings that show promise in delaying the onset of corrosion for significantly longer periods of time, but developers haven’t yet been able to manage costs well enough to make these commercially marketable in the commercial vehicle segment,” he said.

Aluminum also corrodes, though much more slowly than steel. According to Gonzalez, when exposed to humidity and oxygen, a dust develops atop the wheel. It’s not as bad as steel, but it does need to be polished.

Alcoa Wheels sells products ranging from an uncoated aluminum to its premium product, Dura-Bright, which is in its third generation since being introduced in 2002, said Brian Thomas, marketing communications manager.

Thomas points to aluminum’s advantages, including its ability to avoid rust in a tough Cleveland winter. He said it’s 30-40% lighter than steel, an advantage that’s more pronounced in wide-base tires. Alcoa Wheels, in fact, launched a 40-pound wheel a year and a half ago.

And, of course, aluminum wheels require less maintenance. They don’t have to be dismounted and require a simple polishing. For image-conscious fleets, that’s significant. “A lot of tractors and trailers, whether they’re private or for-hire, have their names on their side, so it’s a rolling billboard,” he said.

Thomas said Alcoa Wheels doesn’t endorse any brand of polish. At one time, the company sold a line of products, but the major brands sold in consumer auto parts stores are effective.

Schneider uses steel and aluminum, said Steve Duley, vice president of purchasing for equipment. On the tractor, it installs six aluminum wheels and four steel ones, with the aluminum ones placed on the outside where they can be seen. The practice helps with public perception, improves resale and reduces weight. The carrier’s wide-base wheels are aluminum, too. Meanwhile, to save money, Schneider installs steel wheels on the inside positions.

Trailer wheels also are all steel. “Putting high-value wheels out there on a trailer just kind of makes you a little bit of a target, not to mention the damage you might incur,” Duley said.

To prevent corrosion, Schneider ensures its steel wheels have good priming and paint, and it uses wheel guards between the inside and outside wheels. These nylon plastic plates prevent metal-to-metal contact, retain torque and keep the paint from wearing.

If the wheels become rusty, they are reconditioned and repainted. But that doesn’t happen often — maybe every seven or eight years, he said, which is near the target TMC has requested from manufacturers.

Manufacturers are improving at producing corrosion-resistant components, but corrosion isn’t a new concern, and it’s not going away. Road departments are more concerned with keeping streets safe than they are with helping motor carriers save money. One alternative road departments can use is beet juice, which is less corrosive and more environmentally friendly. But it’s also more expensive.

They’re not going to stop using these chemicals,” Braswell said. “At TMC meetings, even some of the fleets that dump the chemicals on the highways to treat the roads, they would say: ‘A county commission never complained to me about dumping too much mag[nesium] chloride on the side of the road when it’s wintertime. So you’ve just got to understand we’re going to put this stuff out there.’ And their own trucks were rusting out.”