Beware Of Hidden Corrosion

      Surface rusting is mostly cosmetic, and most of the damage is to the driver's pride and the fleet's image. Rear door sills made of regular steel often rust because the paint is easily chipped during loading and unloading. Periodic sanding or sand blasting and repainting keep the members strong and decent-looking.
      However, hidden corrosion can be dangerous. A fleet manager at a recent meeting of the Technology & Maintenance Council of ATA related a near-miss tale involving a group of lightweight flatbed trailers. The problem remained unseen until a driver complained of what he figured was loose jaws on his tractor's fifth wheel.
      Inspection of the fifth wheel turned up no problems, so mechanics looked closely at the trailer's upper coupler assembly. They found that its steel longitudinal members, just above the kingpin plate, had rusted and weakened. The slack felt by the driver was a wobbling kingpin. Had it gone undiscovered, a catastrophic failure could have ensued.
      Inspection of other trailers in the same group found similar corrosion damage, and all were corrected by rebuilding the upper coupler assemblies with stronger materials. The manager did not blame the trailers' manufacturer, because it built the vehicles the way the fleet wanted - with lighter-weight components to save tare weight.
      The problem was aggravated by corrosion induced by aggressive anti-ice salts spread by highway crews. For several years fleet managers had complained of corroding aluminum fuel tanks, steel frame rails and other parts on trucks and tractors, but now it was clear that it affects trailers, as well.