Durability. Cost. Image. Three main factors in fleet decisions about trailer specifications that are directly affected by a common enemy – corrosion. From the roofline to structural members, suspensions, axles, landing gear and upper-couplers, constant bombardment by moisture and debris – as well as exposure to road salts and other de-icing materials – makes specifying trailers for corrosion protection of utmost concern to fleet managers. Equally aware of the challenge are trailer, system and component manufacturers, who are addressing the problems caused by corrosion with new technologies and processes.
Corrosion resistance begins with the design of trailers, says Mark Roush, director of engineering at Vanguard National Trailer Corp.
“Engineering and manufacturing trailers with a long list of standard components that are as corrosion resistant as possible leads to extended trailer life and a superior cosmetic appearance,” he says. “These premium specifications address corrosion before it becomes a problem, rather than after the trailer is in service.”
Vanguard has identified a number of areas where corrosion resistance is essential and has incorporated appropriate design elements in its VXP Composite Plate and VIP 4000 and MaxCube freight vans, according to Roush. For example, galvanized materials are standard on all three of the OEM’s models for rear frames, including gussets, rear underride guards, threshold plates, front aprons on the upper coupler, landing-gear brackets and bracing, mud-flap brackets, front wall posts, internal bulkheads, roof bows and logistics posts.
The company’s trailers also feature a galvanized steel scuff band above an extruded aluminum inner base rail, as well as extruded aluminum front top rails and radius corners.
“We also use a galvanized, one-piece front understructure between the upper coupler and the landing gear,” Roush says, “and galvanized air/electrical channels on each side to protect those system components against the effect of road de-icing chemicals.”
Wabash National Corp. Chief Technology Officer Rod Ehrlich says that trailer corrosion problems have been exasperated, not only just by the type of de-icing chemicals in use today, but also by the amounts being applied.
“We always thought the type of chemical was the biggest factor,” he says, “but we’ve learned that time plays a large role, as well. Road crews are now pre-salting to prevent ice buildup so more chemicals are being used overall. As a result, we’re seeing increased corrosion due to increased exposure.”
Rear frames and doors pose the biggest problem area for corrosion on trailers, according to Ehrlich.
“Most doors on dry-freight trailers are plymetal construction with plywood cores and metal skins,” he says. “The wood acts like an ink blotter and absorbs moisture through any leak, even the smallest hole. The skin is also part of the problem because it is a chilling agent, and as the temperature cools, a vacuum is created, and the door draws in moisture, which travels throughout the core. This process also is impacted by gravity, which is why we see the worst galvanic corrosion at the bottom of the door.”
To prevent this occurrence, according to Ehrlich, Wabash has eliminated plywood from its rear doors and is using a foamed polyethylene core similar to that used in its Duraplate composite sidewalls. The material does not absorb moisture and has the added benefit of allowing door seals to be screwed in place. By contrast, fasteners on wood core doors can act as moisture conduits and are often destroyed by corrosion from the inside. For rear frames, Wabash has elected to use a thermoplastic powder coating that adheres to the steel, which evaluations have shown provides as much as seven times the corrosion resistance.
Corrosion problems on undercarriages are being addressed at Wabash by evaluating different materials.
“For the most part, soft coatings have been better performers compared to paint, which creates a hard shell on the undercarriage that tends to trap and hold moisture,” Ehrlich says. “Paraffin-based coatings, on the other hand, do not harden and aren’t brittle. What we’re investigating today are coatings that react with ferrous metal and bond to the surface. One major issue with this type of coating is that cleanliness prior to the chemical conversion is critical, so surfaces have to be very clean. That can be time consuming, but the end result is probably worth the effort.”
Stainless steel also is in greater use today for corrosion-prevention reasons, Ehrlich says. “As fleets keep trailers longer, they understand that the cost of recoating corroded surfaces makes investing in higher priced stainless steel worthwhile in the first place. We’ve gone to a lower front rail that is all stainless steel for that reason.”
Ehrlich also weighs in on a trailer maintenance issue that relates to corrosion prevention.
“It’s important for fleet managers to be aware that high-pressure washers used to clean trailer sidewalls can create corrosion problems,” he says. “These washers are so powerful that they are capable of blowing seals between wall sheets and allowing water and cleaning solutions to penetrate the trailer body. This is such an important issue that the Truck Trailer Manufacturers Association (TTMA) is developing a recommended practice to help educate fleets about what can happen when pressure washers are used.”
Exposure to ice-melting chemicals; stone and gravel impingement; wide temperature variations and rain and snow all contribute to a destructive environment that requires innovative and advanced-technology coatings for proper rust and corrosion control on trailers, says Chris Stolfe, senior manufacturing engineer at Great Dane Trailers in a recent company newsletter. “Magnesium chloride and calcium chloride are especially destructive because of their ability to cling to the underbody and re-crystallize as they slowly dry out. These chemical crystals attract and absorb moisture from the surrounding environment, keeping them in a semi-solution state for extended periods of time, which multiplies their corrosive nature.”
Great Dane’s undercoating compounds are specifically designed to provide a protective barrier against this harsh environment, Stolfe says. “Dry-Flex” undercoat is a soft and flexible film that’s designed to resist stone chipping and temperature extremes while blocking moisture from reaching the steel components of the underbody. Crossmembers are dipped in a specially formulated, high-temperature, hot-melt wax compound that effectively blocks corrosion by sealing the steel from the environment, the company says.
“Great Dane is working hard to develop new technologies to further enhance underbody corrosion control,” Stolfe says. “Thermoplastic coating of steel underbody components is currently in testing, and advanced chemistry for soft coatings, which will provide greatly improved corrosion resistance against magnesium chloride, is under development. Both new technologies may be available in the near future.”
Great Dane’s efforts are important, noted Michael Bourdeau, director of reactive cure at Valspar Corp., in the trailer OEM’s newsletter, because a poor coating selection can cause premature rusting on trailers, which adversely affects the aesthetics of the trailer and potentially shortens longevity. One of the technologies already adopted by Great Dane for corrosion protection is R-Cure, supplied by Valspar.
In particular, Great Dane facilities are utilizing a two-coat process with R-Cure 200 epoxy primer initially applied to the trailer, followed by the R-Cure 400 urethane topcoat. The epoxy primer material, according to Bourdeau, is very forgiving under different substrate conditions, something that has been demonstrated at Great Dane as additional metal substrates are added to the trailer, including galvanized metal. The R-Cure 200 epoxy primer, he says, has been able to coat these different surfaces without any difficulty in adhesion, which is one of the major concerns as conditions vary.
Primary causes of corrosion on trailer components, according to Steve Dupay, director of research and development at The Holland Group, include new chemicals that road departments are now using, as well as the mix of de-icing products that trailers are exposed to in different states. “Rust problems are accelerating,” he says. “While the cost of corrosion on trailer components is not easy to quantify, feedback from customers indicates that it is a growing concern.
“We’ve heard from fleets and OEMs that they are tired of the appearance problems that corrosion creates,” Dupay says. “Some fleets spend a considerable amount of money to refurbish trailer components because they have high-profile operations and want to maintain their company image. There’s also the possibility that corrosion impacts longevity, so they are asking for a proactive approach in developing products that will stand up to corrosion longer.
“Terminally pervasive corrosion on trailer components is not sufficiently addressed by standard paints and coatings,” Dupay says, “because they don’t bond sufficiently, have poor resistance to chipping caused by foreign objects, as well as moisture, heat cycles and UV exposure, and are generally not tested in real-world road conditions. Standard paint technology to protect from corrosion on trailer components comes at a price and does not generally buy a lot of extra time.”
The Holland Group’s answer, is called Black Armour, a coating that is designed to react with any metal that oxidizes, and, in effect, destroy corrosion.
“It causes steel to grow a new protective skin that is 10 times more impervious to water than a swimming-pool coating,” Dupay says. “It has a corrosion package that never allows it to shrink, and it also compresses, which means that, if it is struck hard, it does not shatter but remains intact.”
Compatible with a growing list of Holland landing-gear products – including Challenger 5000 Series, Fastgear FG4000 Series, Mark V Series and Contender 51000 Series – Black Armour actually refers to a base coating that meets a prescribed performance factor. The same coating also is being used on some of the manufacturer’s suspension components and will be called by the Black Armour name once it meets standards in those applications. The coating also can be top coated with any paint and does not require pre-sanding, meaning existing trailer components can be refurbished in a cost-effective manner.
“The key is performance,” Dupay says. “Historically, everybody looked at salt-fog hours as a key measurement, but the heavy-duty industry is recognizing that salt-fog testing doesn’t apply because some products did well in tests and poorly on road. Most manufacturers now subscribe to SAE J2334, a cyclic cosmetic corrosion test that accelerates exposure and more accurately simulates real-world requirements. Also in use is SAE J400, a chip-resistance test that involves firing calibrated gravel with a pneumatic gun at the component to see how the coating holds up. Both of these are aggressive and effective standards.”
The product behind Holland’s Black Armour, which also is in use by some trailer OEMs and fleets, is supplied by PRP Industries. Called CORSOL, the corrosion prevention treatment is used in a variety of applications, including commercial vehicles. Typical applications include corrosion prevention for truck bodies and truck and trailer frames, cabs, suspension components, crossmembers, axles, springs, trailer door frames, upper coupler assemblies, lift gates and steel wheels.
CORSOL, according to PRP, is an extremely stable single-component, air-drying, air-curing anti-corrosive that is galvanically non-conductive, which allows dissimilar metals to be fastened together without concern for corrosion around joining surfaces. The company’s 200 Series coatings can be applied directly to clean metal surfaces with no need for primer. 500 Series coatings from PRP are especially suited for any structural steel application requiring high corrosion and heat resistance up to 600º, according to the company.
Corrosion protection on trailers also requires proper maintenance. Trailer OEMs, for example, advise frequent pressure washing of undercarriages to remove corrosive chemicals, especially during winter months. Additionally, repairing damaged areas of any coating as soon as possible will help prevent corrosion that can spread.
Also spreading the message about proper maintenance to reduce the impact of corrosion on trailer components is lighting and electrical systems supplier Truck-Lite Co. For example, one of the questions and answers on the company’s Web site is as follows:
Some of the electrical pin connectors in my plugs have completely corroded away. What can I do about this?
“We use the most corrosion-resistant metal available in the plugs, but if water or ‘conductive’ dirt gets in the plug, it can provide a short cut for the voltage, which corrodes away the metal in the plug. The answer is to use new plugs and plenty of grease. If possible, move the lights to a more protected area and/or add a module box for protection.
“Treat the electrical system as you would the chassis,” Truck-Lite also advises. “Lubricate sockets, pigtails, battery terminals and connections with a non-conductive anti-corrosion compound. The purpose of the sealant is to totally encapsulate and protect against corrosion and water.”
On the list
Grote Industries lists corrosion as one the “eight major causes of safety lighting failures.” Solutions suggested by the company include specifying lighting products that are sealed because corrosion around the bulb sockets cannot approach the bulb when it is sealed within a lamp housing.
“To further protect against corrosion, all electrical wiring connections should be sealed against moisture with a non-conductive, non-sodium based grease, in areas like electrical contacts, circuit switches and junction boxes, the company says. “The purpose of this sealant is to totally encapsulate the area to protect it from the elements.”
Environment is one the most damaging elements for trailers. “Winter puts trailer wiring systems through the greatest salt attack known throughout history, Grote literature states. “Eleven times more salt is put on the highways during the short winter season than the total population of the U.S. puts on the table or uses for food preservation and preparation in a year.
“During summer months, wiring is exposed to heat and direct sun rays,” the company says. “Environment greatly magnifies any known abuse. It finds any unprotected wire end or improper splice and introduces salt throughout the wiring system. The result is corroded wire and greatly increased resistance and temperature, all leading to harness as well as lamp destruction.”
Major discussion point
Corrosion has been a growing issue for the past decade or so, but has really become a major discussion point in the past four or five years, according to Travis Hopkey, director of marketing at Phillips Industries.
“The problem still exists and continues to grow,” he says. “Among the primary causes of corrosion are chemicals and improper maintenance procedures. Salt, magnesium and calcium chlorides used on our nation’s highways to help de-ice the roads have a negative effect on all metals, including electrical connections. The biggest issue with magnesium and calcium chlorides is that they stay wet down to about 15 percent humidity. Even the Mojave Desert in August has greater humidity. The result is that the chlorides are still wet to the touch and continue to eat away at the metals.
“With proper installation and maintenance, a trailer harness will last the life of the trailer,” Hopkey says. “For example, any mechanic who is making an electrical repair should use a heat shrink connector. Standard PVC and nylon connectors do not protect against water and contaminant intrusion because they are open-ended and allow water and chemicals to penetrate the harness system. Heat-shrink connectors offer the best of both worlds – a mechanical crimp that holds the wire and terminal together and shrink tubing that protects against contaminants.”
Hopkey pointed to the Phillips STA-DRY product line, which is designed to fight corrosion as one of the manufacturer’s answers to the corrosion challenge. Most recently, the company introduced STA-DRY in-line, closed-end and step-down connectors for effectively joining multiple wires to preserve a sealed electrical system. The color-coded tubing has an active adhesive that seals between multiple wires, eliminating wire pull out, the company says. In-line butt connectors join two wires into one, replacing temporary unsealed Quick-Taps. The closed-end connectors join two to four wires and can replace wire nuts in environments where corrosion is a problem. Step-down connectors allow for different wire gauges to be joined together.
A 2004 study by independent breakdown service provider FleetNet America cited “wiring and connectors” as one of the top-10 reasons for truck breakdowns due to failures from “corrosion, improper splicing and/or routing, and impending damage.” Driven by that data, Sloan Transportation Products has developed a sealed plug, that when combined with the receptacle, provides a contaminant-free connection between tractor and trailer, according to the company.
Part of the company’s new MAXXDuty with WeatherGuard Technology product line, the Sloan TriMAXX 7-Way sealed plug system, features an integrated plug-face gasket that ensures a positive seal to the receptacle, eliminating corrosion from reaching the terminals, the company says. The gasket, made of PVC, encircles the terminal area, creating a sealed union regardless of receptacle’s manufacturer.
The most direct path for corrosion to attack an industry standard plug and socket connection, according to Sloan, is for contaminates to back flow down the cable. To prevent this, the TriMAXX System features over-molded terminals, Sloan says. In addition, the system has an integrated drip-edge channel that eliminates back-flowing contaminants from coming down the cable into the plug/socket connection.
Many fleets understand the problems associated with corrosion and are spec’ing vehicles to withstand the impact of these chemicals. Many suppliers, likewise, are hard at work developing effective solutions.
Corrosion Prevention Tips
• Use heavy-duty heat shrink tubing
Use heavy-duty, adhesive-lined heat shrink tubing on all electrical connections.
• Protect battery posts and terminal with anti-corrosive spray
Use battery protector spray on battery connections.
• Check ground power source
Always make sure ground leads directly to the negative battery post. Grounding to the chassis or engine will lead to corrosion, poor contacts and faulty electrical operations.
• Store electrical and air coils
Use stowage devices when electrical and air coils are not in use for extended periods of time.
• Rotate electrical assembly plugs
Safeguard against uneven wear; swap plug ends from tractor to trailer side every six months.
• Do not pierce wire jacketing
Never puncture a hole in the wire jacketing. This causes wicking, which creates a leak path for contaminants to seep in, which rots the wire from the inside out.
• Wash away build-up
Frequently wash equipment during cold weather to reduce magnesium and calcium chloride build up. Do not power wash because water can be forced into areas and cannot escape, which leads to corrosion.
• Grease plugs and sockets
Re-apply dielectric grease on plug and socket pins after every cleaning.
• Clean connectors
Every six months use a plug and socket brush with water (no soap) to clean connectors.
• Inspect cables and wires for road hazard damage
Replace or repair damaged items.
• Be cautious of soaps containing degreasers
When degreasers come into contact with electrical connections, it increases the corrosion reaction. Do not leave soap residue on electrical connections.
Source: Phillips Industries, see www.phillipsind.com for more information.
It’s not a coating or a finish, said Alcoa, but rather a patented treatment that penetrates aluminum wheels to protect against oxidation and corrosion. “Commercial vehicles operate in demanding highway and urban environments,” the company says. “To withstand these conditions, we developed Alcoa Dura-Bright wheels.
“On ordinary aluminum wheels, a coating is typically a layer of baked powder that sits on top of the wheel surface,” the company says. “With Alcoa Dura-Bright wheels, the treatment actually penetrates the aluminum, forming a protective barrier that becomes an integral part of the wheel and completely eliminates the cracking, peeling and corrosion common in coated wheels.”
For more information, visit www.alcoa.com.
For more information from the suppliers mentioned in this article:
Vanguard National Trailer Corp.
Wabash National Corp.
Great Dane Trailers
The Holland Group
Sloan Transportation Products