LIQUID magnesium chloride has a boiling point of between 203°F and 212°F. But if you were to rest a beaker of it on the forehead of those in the truck and trailer industry who blame it for the severe and rapid corrosion they have seen in their equipment, 98.6°F would be enough.
Although corrosion is occurring in coastal areas because of salt air and humidity — electrical connectors and systems are particularly susceptible — magnesium chloride is the flash point igniting the uproar of this new millennium.
“We're getting vociferous feedback from our members,” says Vic Suski, the American Trucking Associations' program manager for winter roads management. “It's a huge subject.”
Suski calls himself the “archaeologist” of the corrosion issue as it relates to the truck and trailer industry. He's digging all over the country to ascertain what is happening — what fleets are reporting is occurring on their vehicles, what studies are being conducted and the conclusions that are being reached, what states are doing in response to the outcry, what equipment manufacturers are doing to develop more corrosion-resistant coatings — with the ultimate goal of unifying the effort.
“The problem is that there are so many people working in isolation,” he says. “They're not really talking to each other. It's all over the map. It's a huge problem and a huge effort, but it's not connected.
“The people working on the problem need to be told, ‘There are other people working on another aspect of the problem, and if you work together with them, you'll help us.’ The state highway departments don't know how critical it is for us. They need to be educated.”
He says he will be turning all the information to the ATA's Technology Maintenance Council (TMC), which eventually will write recommended practices. But those must be based on knowledge, and assembling the corrosion library is a daunting task.
“I can't give you determinations or conclusions because this is just starting to be addressed,” he says. “We can't even definitively define the problem yet. But we know it's a big problem. It's all based on fleets telling us, ‘We've got a heckuva problem.’”
Many state highway departments have increased the use of liquid magnesium chloride as a dei-icer or anti-icer, spraying it on dry pavement prior to precipitation or wet pavement prior to freezing temperatures to lower the freezing point of water and prevent snow and ice from bonding to the surface.
According to a 2002 study by the Colorado Department of Transportation's research branch, “Corrosion Effects of Magnesium Chloride and Sodium Chloride on Automobile Components,” over four million gallons of magnesium chloride have been used per year in Colorado because it has been effective in clearing the roads and is the most cost effective option (at 30 cents per gallon). The state has experimented with Ice Slicer, a granular product that is costlier ($75 per ton); Ice Ban, which costs at least twice as much as magnesium chloride; and Calabran M 1000, an alcohol-based solution that works better than magnesium chloride in colder weather and is less corrosive, but also costs more than twice as much.
Many fleets and equipment manufacturers believe the proliferation of magnesium chloride usage correlates directly with the increase in corrosion they have seen in their vehicles and equipment. An American Trucking Associations Foundation survey published in 2002 showed that 72% of Colorado trucking companies reported increased wear on their equipment since the state's DOT started using magnesium chloride.
In some cases, it's mere cosmetic damage, with the chemical causing scarring of surfaces.
But the damage can be a lot more severe. The effects of magnesium chloride is believed to be seen on metals of all kinds, on wheels, rims, trailer landing gear parts and suspension parts, hoses and connectors, electrical wiring, frames, and fuel-tank straps. The specific type of damage mentioned in the Colorado survey most often included corrosion, pitting, staining/tarnishing, discoloration, drying/cracking, and accelerated rust. There have been reports of fleet maintenance personnel pushing soft instruments all the way through structural elements on trailer suspensions that had been suspected of being rotted by magnesium chloride.
There are reports of wiring systems that have been deteriorating at previously unseen rates, with the chemical suspected of wicking into connection points and attacking copper wiring.
One tire store has a prominent display that documents what it believes are the direct effects of the chemical — including brakes that have to be replaced at 20,000 miles instead of the normal 60,000.
The belief is that magnesium chloride is causing rust jacking by infiltrating brake shoes, eating the shoe table and cracking linings, thus reducing the lining life by half and impacting brake safety.
Task force formed
Vern Caron, director of commercial vehicle electronics for ArvinMeritor's heavy-vehicle system and chairman of the Society of Automotive Engineers' Brake Committee, says the issue of rust jacking first came up two years ago. After floating the issue to the SAE's Truck and Bus Council, he formed a task force to investigate better specifications for commercial-vehicle corrosion testing. They've been meeting for more than a year to try to assemble an improved standard.
“In the studies that have been done, we're finding that 1% of the shoes that show up for aftermarket reline show evidence of rust jacking,” he says. “The corrosion of the brake shoe is so severe that it limited the life of the lining. In other words, you had to replace the shoe before the lining was worn out, because of corrosion.
“There's a lot of discussion about the origin of shoes, whether they're OEM shoes or aftermarket shoes. There might have been shoes that went through the cycle a couple of times. They might have been relined once and come back through. It's difficult to make much out of the rust jacking situation, but we're continuing to work that angle.
“Magnesium chloride is a real political discussion. It may have some nastier characteristics in the way it's used and applied, the evidence of this is anecdotal. We have lots of nasty photos, but it's difficult to put together hard statistical evidence. It's so emotional. People are so negative about magnesium chloride.”
How emotional? One day in 2003, the Board of Montana Flathead County Commissioners convened at 8 am to discuss two key questions: Was magnesium chloride impacting the safety of private and commercial vehicles through corrosion? Was it impacting the infrastructure of roads, bridges, culverts, signs, watersheds and ground water? By 5 pm, they still hadn't adequately addressed the issue, so they came back the next day.
Among the items discussed:
The county was receiving 20 to 30 complaints daily from upset residents.
A man reported that his new $50,000 rig already was rusting on the bumpers.
Magnesium chloride will stay moist at a relative humidity above 27%, but even if it does corrode less per event by staying moist, it will corrode longer.
Although magnesium chloride producers claim they have integrated a corrosion inhibitor to negate damage to vehicles, the Colorado DOT study showed that the inhibitor wasn't effective.
Maintenance professionals say that once magnesium chloride wicks into a joint between two metals, it's there to stay unless the pieces are disassembled, cleaned, and painted.
State of Montana fleet manager Jack May reported that the worst problem was the way the chemical attacks wiring, adding that if a wire has been probed, corrosion will eat through the conductor in a week. He said the deicer will seep into junction boxes and electrical components with wiring connections and circuit boards and quickly destroy them.
Mechanics were pulling off brake lines that weren't even 50% worn, but were cracked, loose around the rivets, and showed a very uneven lining wear. What if they aren't replaced when they should be? The question was asked, “If there's a heavily loaded semi truck coming through Columbia Falls, Kalispell, or Whitefish, and its brakes fail because of corrosion caused by this road deicer, how many people are going to get hurt or killed?”
Magnesium chloride was attacking concrete and steel in many of the state's 2,100 bridges, necessitating expensive resurfacing or replacement.
An employee of John Jump Trucking said that corrosion of wiring was affecting computer controls, causing the engine to shut down. Also affected were pig tails on trailer cords for lights and scales. Corrosion of parking brake air cans could cause failures and accidents.
“Why can't we get back to like we were 50 years ago?” one attendee asked. “Slow down and just plow the roads.”
Of course, it's not that simple. Some mountain towns in Colorado — including Aspen, Fraser, and Winter Park — have banned the use of magnesium chloride. But because of its cost effectiveness in terms of application, it's not going to completely go away.
What is the cost?
Suski says TMC is trying to help states understand that while magnesium chloride may be cheap and effective at keeping the road clear, the overall cost to the states may be far greater than they recognize.
“Everybody has a problem, but there are very few people working to solve the problem, because the states' problem is not corrosion, it's keeping the roads clear,” he says. “Then it gets involved with politics. No state highway guy wants to lose his job because of complaints about snow on the road.
“But if you add up all the damage to the truck fleets domiciled in those states, maybe the more expensive chemicals aren't that expensive after all. Right now, the states are strictly focused on getting the roads clear. We want clear roads, too, because we've got to travel them. We're trying to point out that if you add up all the money you lose on corrosion of your own vehicles — and that's not just trucks laying down salt, it's cars used by state officials — and corrosion on bridges and inspecting bridges for corrosion-induced damage, then a benign chemical may not be that much more expensive. A cost-benefit analysis has to be done.
“There has to be a better way. We're saying (the current use of magnesium chloride) is overkill. We're using a sledgehammer when we should be using a small hammer. The brute-force approach is the most obvious, easiest, and cheapest. But there has to be a better way.
“Fleets are in a bind. Some people say, ‘Wash your trucks more often.’ Others say, ‘But when that magnesium chloride gets down on the concrete where the truck is standing after being washed, that gets slippery and people fall.’ Other people say the mechanics are getting respiratory problems when they get near trucks that had magnesium chloride on them before they were washed. Other people say they're not allowed to wash their trucks in their jurisdiction. Others say when they wash their trucks they get on the verge of being cited by the state Department of Environmental Quality because the runoff has too many noxious chemicals. It's OK to put them down on the highway, but don't wash them off? That's the bind we're in. Where does it say that the government has to be logical?”
Another problem is that although studies have been done on corrosion, they have produced sometimes conflicting results, and not enough studies have been done.
The 2002 Colorado report consisted of two phases. In the Phase I study, the relative corrosiveness of magnesium and sodium chloride was examined by SAE J2334 test and American Society for Testing and Materials (ASTM) B117 test. In the Phase II study, SAE J2334 test and National Association of Corrosion Engineers (NACE) TM-01-69 test (as modified by the Pacific North States) were applied. Representative metals examined in the project included stainless steel 410 and 304L, aluminum 2024 and 5086, coated automobile body sheets, copper wires, and mild steels.
Experimental results of SAE J2334 test indicated that magnesium chloride was more corrosive than sodium chloride to the bare metals tested. However, the experimental results of ASTM B117 test showed the opposite. Because of the conflicting conclusions, further tests were conducted using NACE TM-01-69 (as modified by the Pacific Northwest Snowfighters). Again, opposite conclusions were obtained from SAE J2334 and NACE TM-01-69 tests. In order to investigate the causes responsible for the inconsistency, the experimental conditions of both tests were modified and the various modified modes of the two tests were conducted.
According to the report, “It was found that the inconsistency in the test results was not a result of different chemical concentrations of chloride solution, different immersion times, testing periods, or testing temperatures. It was attributed to the different moisture conditions and different properties of the two salts under high-humidity environments. There were three basic moisture conditions in the three testing methods used in the project: dry, wet (saturated moisture), and dip (immersion). Since the magnesium chloride solution has higher viscosity and stronger hydraphilicity than the sodium chloride, it is much easier for the magnesium chloride to stick and crystallize on the surface of the metals under the dry condition, and then become solution on the metal surface under the wet condition. This dry-wet effect is responsible for the different corrosion behaviors of magnesium chloride under different testing conditions.
“Therefore, depending on service conditions experienced by automobile components, magnesium chloride is more corrosive than sodium chloride under humid environments, and sodium chloride is more corrosive under immersion and arid environments.”
Suski says he is communicating with the US Army's Aberdeen Test Center in Aberdeen, Maryland, which is capable of conducting accelerated tests that in 220 days can simulate 20 years of corrosion activity on the roads — but that's strictly with sodium chloride. Caron says he's been communicating with the center to determine if tests can be done using magnesium chloride.
The center's Accelerated Corrosion Complex provides aggressive controlled exposure of corrosive conditions to land systems to hasten their weathering process and determine susceptibility to the environments. It includes a series of individual corrosive environments: mist booth (60'×15'×15'), with up to a three-minute mist applied to top and vertical surfaces; splash trough (75'×20"), with solution depth up to 2" subjected to undercarriage; grit trough (75'×14'), with slurry depth up to 8” subjected to undercarriage; and humidity booth (40'×15'×15'), with up to 160°F, 1 to 2 ml/hr condensate.
Meanwhile, out in Richland, Washington, the Pacific Northwest National Laboratory (PNNL) is nearing the end of a two-year corrosion study done in collaboration with the Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee. Both labs — which are part of the US Department of Energy's Office of Science — perform a wide range of science and technology research for DOE, which is pursuing this project because of the implications of heavy-vehicle corrosion on weight saving, energy-efficient materials, and vehicle safety.
The approach is to: evaluate heavy-truck corrosion damage to identify materials, components, and safety-related items affected by anti-icing/deicing treatments; identify and characterize magnesium chloride solutions and corrosion-inhibiting additives; perform accelerated corrosion testing and corrosion characterization of heavy-vehicle materials; evaluate brake-shoe failures to identify aggressive corrosion species and the extent of corrosion; determine the thermo-elastic and mechanical properties of the lining material, brake-shoe table, and corrosion products; incorporate the mechanical properties of the lining material, brake-shoe, and corrosion products into computer-aided engineering (CAE) codes to predict the stresses associated with swelling of oxides on the shoe/lining interface; identify more desirable ice-clearing chemical formulations and application methods; and generate “best-practice” recommendations for reduced vehicle corrosion and improved safety.
A corrosion field evaluation was performed last winter in collaboration with the Montana DOT (MDT). Corrosion coupon racks were placed on select MDT liquid-dispensing and abrasive trucks that were exposed to different ice-clearing chemicals and winter conditions in various regions of western Montana. Regions were designated in which corrosion-inhibited calcium chloride and corrosion-inhibited magnesium chloride was the sole chemical used.
To include sodium chloride exposure as part of the text matrix, the Utah DOT allowed MDT to place four corrosion coupon racks on their liquid-dispensing trucks (also designating a region as the sole chemical used). Coupon racks also were placed on two commercial haulers traveling the US throughout the winter season to include a national, mixed-exposure of ice-clearing chemicals. As a control, one coupon rack will be placed on a rooftop exposed to the environment only.
The corrosion coupon racks consisted of two coupon panels of CR 1008 steel, A356 cast aluminum, and 5182-O aluminum. All coupons were electronically isolated to prevent any electrolysis between the corrosion coupon panels and the mounting rack. The coupon rack was attached between the frame rails behind the rear differential, with the coupons hanging down.
Half of the corrosion coupon panels on each rack were removed at the end of the winter season, while the remaining panels stayed on the truck. The first set of coupon panels is being evaluated, with conclusions expected by October. The other set will be exposed to an additional winter season, and the labs will be adding stainless steel and chrome steel to the coupon racks.
In addition, they are doing accelerated corrosion laboratory tests, including the same alloys used in the field evaluation, plus 5052-H32 and 6060-T6 aluminum alloys. Elizabeth Stephens, research scientist at PNNL, says that came as a result of an assessment done after talking with a “prominent trailer company here in the Pacific Northwest.
“From our background, it was difficult because there wasn't any significant data to quantify the role of magnesium chloride treatments on heavy-truck components,” Stephens says. “It's just the strongly voiced opinion within the trucking community. There was a lack of data, so that's why we're trying to quantify it by evaluating corrosion damage to see if there's truth to it.
“There is something occurring, but we do not really know fully to what extent and exactly what is contributing to the problem. Is it solely magnesium chloride? Is it the mix of magnesium to sodium? Not knowing what commercial haulers are being exposed to, it's difficult to characterize.
“We're trying to restrict areas of where it's been exposed to and even included mixed exposures. So I'm hoping we will have a good idea of what is occurring and what we're seeing.”
Then there's the whole issue of anti-corrosion coatings.
Heil Trailer International has worked with DuPont to devise a combination of coatings that best resist corrosion caused by magnesium chloride. As part of its standard offering, Heil sand-blasts the surface to make sure it's clean, applies a zinc-rich primer, and then Imron 5000 as the finish paint. Heil charges a premium for the customer who wants a full paint job — the vessel as well as the steel members that are the frame structure and hold the run gear onto the trailer.
Heil also offers an alternative method on the trailer's steel-frame components in which they are galvanized — at an estimated charge of $2,000 per trailer.
“Depending on the application, both have been effective to this point, from what we see,” says Bill Boyd, vice president of purchasing and formerly in the engineering department. “With the painted approach, if the vehicle is going to have a lot of highway miles on it and it encounters a magnesium-chloride treatment, it holds up good. If that unit is on a lot of gravel roads where there's a lot of kick-out and gravel penetrating the coating, and then it's exposed to magnesium chloride, you're going to see rusting — and there's not a lot you can do about it.
“The galvanized solution, by its very nature, is kind of self-healing if it takes a rock strike. Most highway retaining guard rails are carbon steel that have been galvanized, and they appear to be standing up over time.”
ArvinMeritor, a primary OE brake supplier, has been using epoxy e-coated brake shoes for over 10 years.
“If you talked to any supplier, he'd tell you he'd be happy to make components out of platinum or gold or anything people are willing to pay for,” Caron says. “The issue is, there are going to probably be a variety of corrosion-protection levels possible. It's a matter of negotiating with the end user as to what amount of corrosion protection he feels he needs, and what he is willing to pay for. You may or may not be willing to pay to get more corrosion protection.”
Says Suski, “There is a lot of work in advance coatings, but their long-term efficacy is not yet known. Vehicle manufacturers have a role to play, and the chemical industry has a role to play. There are some people who say they have more benign, less corrosive chemicals for anti-icing and deicing, but they're very costly. The two paths have to be followed, and there has to be a crossover point where enough is done in getting more benign chemicals and enough is done on better coatings and treatments. They're going to have to merge, and we'll have a good compromise solution that doesn't discomfort anybody too badly.”
But for now, everyone is hunkering down in the midst of the corrosion explosion, looking for answers that won't come easily.