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The Road to Ruin
At the TMC Meeting in 2001, Roy Gambrell shocked the truck maintenance community by making everyone aware of a new phenomenon — rust jacking. Gambrell, the director of maintenance for Truck It, a small flatbed operation in Franklin, Ky., found that his fleet’s brake linings were cracking after only 30,000 to 40,000 miles of service. When shoes had been repaired or replaced, the cracking was found to occur even more rapidly.
The cause of the cracking was rust jacking. It occurs after corrosive chemicals are applied to the roads to prevent or control snow and ice. As tires roll over the roads they kick up fine sprays of the chemicals. The moisture carries sodium chloride, calcium chloride and magnesium chloride, often in combination. It gets into the nooks and crannies of a truck’s structure. When spray and chemicals get onto the steel brake shoes, they cause rust. Rust, or iron oxide, expands to a greater volume than the original iron it combines with. That expanded material has nowhere to go, so it presses outward against the weakest point of resistance, the brake linings. Eventually the pressure becomes great enough to crack the linings. If caught early, the cracked linings will just put a truck out of service. If not caught in time, brakes can fail catastrophically. That causes crashes.
Shortly after Gambrell identified the problem, Darry Stuart, president of DWS Fleet Management Services, presented photographic evidence to TMC that demonstrated how widespread corrosion had become. It wasn’t only brake shoes that were affected. Stuart demonstrated that virtually everywhere on a truck that metal is exposed, the metal can be attacked. Suspension parts abraded by sand and gravel, aluminum and steel fuel tanks, landing gear, cab steps and even cross members and chassis rails have rusted to the point of losing all structural strength.
Corrosion isn’t confined to structural parts. Glad hands have deteriorated to the point where they will no longer hold air. Tank straps and related hardware have corroded through so they can no longer support the tanks. Hose end fittings have been found to be so corroded, they can no longer keep hoses attached, and brake air chambers have rusted through so that brakes no longer work. Imagine coming out of the Eisenhower Tunnel or going down the Grapevine with one or more brake chambers rusted through.
Spot the rust
The nature of these chemicals is that, in a vapor-borne solution, they wick into the joints between two metal surfaces and stay there even through numerous washings. Magnesium chloride is one of the worst offenders. While less aggressive than ordinary road salt, magnesium chloride stays moist longer and does more total damage over time. If the relative humidity is above 27 percent, magnesium chloride will stay wet continuously.
While many surfaces might look damage-free, they may be rusting from inside out, often in the spaces between metals. At the first sign of corrosion on the surface, clean whatever you can. Then, try to inspect and clean in the cracks. You may have to disassemble components to get to where the rust starts. Sprays and paints that chemically convert rust are a good stop-gap measure, but for a long term fix abrade or sand blast down to bare metal. Then prime and paint.
Many fleets pay thousands of extra dollars up front to get galvanized or even stainless steel components. As with sealed wiring harnesses and plugs, long life components pay for themselves many times over the life of a trailer. If your equipment doesn’t have these long-life components, consider them when it’s time to replace parts. When performing maintenance, use the best quality products you can get. Inexpensive brake shoes that you replace three times a year or suspension hangers that rust through are no bargain. Powder coated products that have epoxy or urethane resins drawn to part surfaces with electrostatic charges, and then baked to melt and flow the particles into all nooks and crannies provide the longest coating life, even in the most adverse conditions.
Long truck and trailer life starts with spec’ing the best components. Make sure they’re suitable for the job, then select on the basis of corrosion protection. That applies to replacement parts as well as new. The next step in fighting corrosion is cleanliness. It’s a good idea to wash every truck regularly. When you consistently travel through salt spray, wash more often. Pressure washing works well on trailer sides and tops, but around the undercarriage high volume flooding may be more effective. After washing and during your pre-trip inspections, check for any signs of rust or galvanic action between metal parts.
Take your time. Be thorough in all you do: cleaning, painting, inspection and repairing. You’ll get the longest possible life from all your rolling stock.