By Paul Abelson
Senior Technical Editor
In the last year of the 20th century, trucking became familiar with a new term, one it wished it never heard – “rust jacking.”
It was brought to the industry’s attention by Roy Gambrell, maintenance director for Truck It Inc., a 26-tractor flatbed operation in Franklin, KY.
Gambrell, now a member of the Technology and Maintenance Council Board of Directors, started experiencing brake failures after only 18 months of service. Edge cracks completely through the bridge linings appeared suddenly and frequently.
When he pulled the wheels, Gambrell found the cracks ran clear across the linings. They were traced to buildup of rust on the face of the brake tables. The linings, held by rivets, could not resist the stress as the rust expanded. Instead, they cracked.
Gambrell brought the problem to the TMC board. Other members mentioned seeing this and other corrosion-related failures. Investigation led to one conclusion: Rust jacking and increased corrosion are directly traceable to the increased use of more aggressive snow- and ice-fighting chemicals.
Rock salt (sodium chloride) has been used to lower the freeze point of ice since the 1950s, and is often mixed with sand or cinders to increase traction. Passenger car and light-duty vehicle rusting increased in the 1970s. The auto industry responded with more non-corroding materials and improved coatings. Cars today are far less susceptible to rust, at least from salt. But resistance to salt alone is no longer enough.
In the late 1990s, highway departments found they could reduce costs by taking advantage of more aggressive snow-fighting chemicals. When they used rock salt, they had to position the snow plow-salt spreader combinations at regular intervals to wait for heavy snowfall or freezing rain. The trucks idled, wasting fuel and creating pollution. Drivers were paid to sit and wait, and then paid overtime when they were finally dispatched.
By adding magnesium chloride, calcium chloride and various acetates, highway departments could change operations. Mixtures were spread in anticipation of snowfall, to remain in place until snow actually fell. The mixtures would then melt the snow.
This usually gave the departments time to call up personnel and dispatch trucks, saving idling and overtime. Granular salts might be blown away, but spraying liquid compounds on the roads would leave the chemical coating to do its work later. Many departments started applying the mixtures, or brines, to the roads. The savings met and exceeded expectations – but the consequences were horrendous.
From the time the brines were spread until the snows actually fell, hundreds or thousands of vehicles passed over the roads. Each sprayed a small amount of the liquid into the air.
Even when the water evaporated, tires kicked up fine crystal dust. Most of it settled back on the roadways. Some settled on and in vehicles, permeating cracks and crannies, including those spaces between brake shoes and tables.
“Deliquescence” is the process of melting or becoming liquid by absorbing moisture from the air. Both magnesium chloride and calcium chloride are deliquescent. They are used on dirt roads in the west to hold down dust. The property that keeps dust controlled also draws moisture to the nooks and crannies of modern trucks, setting up the rusting process wherever the chlorides contact bare metals.
Rust jacking in brakes led to the discovery of this modern corrosion process, but it is certainly not confined to brakes alone.
Mild cases of rust jacking discovered during an inspection will put you out of service. Severe cases could render one or more brakes ineffective. Shoes and tables aren’t the only parts affected by the chemicals.
Chambers can, and do, corrode clean through, creating extremely dangerous conditions. Chemicals enter the perforated steel chambers, where they destroy air brake return springs. With the spring gone, the brake drags. That can cause premature wear at best, and a wheel or tire fire at worst.
If the rust-through occurs at the spring (parking) brake chamber, the result could be explosive. Weakened chambers can fail, releasing all the force of the compressed spring. Such failures have caused injury and death. If the brake spring corrodes, parking and emergency braking is lost.
While not as immediately dangerous as rusted brake chambers, corroded gladhands cause leaks in the brake air system. Depending on which gladhand fails, this leads to either the emergency brake coming full on, “dynamiting” while you’re driving, or having no trailer service brakes.
Most owner-operators opt for aluminum fuel tanks. They clean up nicely, save weight and resist corrosion. The key here is to resist, prevent corrosion.
TMC members report corrosion under straps and where the tanks sit on their brackets. Just as metals containing iron rust, turning into iron oxide, aluminum becomes aluminum oxide. Because of corrosion, this otherwise useful material becomes weak, prone to puncture from the smallest forces. In fact, one sign of corroded fuel tanks is fuel seepage around hangers and straps.
At the TMC meeting, several fleets reported that radiators, especially with aluminum cores, were failing at unprecedented rates. Heat transfer fins, subject to physical damage from road debris, gravel, sand and stones, had been eaten away by chemicals. Coolant tubes and top tanks had been perforated, and the new aggressive chemicals attacked even stainless steel coolant pipes.
More structural damage has been reported on trailers than on tractors. Wherever dissimilar metals, such as steel and aluminum, are found together, galvanic (electro-chemical) reaction is much greater than with single metals.
Common problem areas are front bulkheads, upper coupler plates and suspension hangers. Longitudinal frame rails rust anywhere that their protective paint has been compromised. Cross members are weakened structurally by corrosion. It often occurs inside the contours of the cross members, where it is difficult to see during normal pre-trip inspections. When one cross member is affected, usually most others are, too.
Corrosion is an electrochemical process. Whenever you already have electric current, corrosion will be accelerated in the presence of salt sprays. Moisture easily enters bulb-replaceable clearance/marker and stop/turn/tail lamp housings, corroding sockets and wiring. Even with sealed lamps, connectors are susceptible. Terminals, battery posts and clamps can get corroded to the point where current is broken. Despite being embedded in rubber, seven-pin connector cords are especially vulnerable. They sit in a space where spray is churned and permeates everything, and the connector pins are often attacked.
Corrosion affects hangers, steering gear, tie rods and control arms and even air bag mounts, both top and bottom.
Rusted engine blocks are rare, but oil filters and oil pans have been perforated by rust.
The industry has finally recognized how severe the problem of corrosion has become. While we wait for highway departments to change their formulas, suppliers to develop effective but non-corroding chemicals and manufacturers to build rustproof trucks, there are steps we can take to protect our equipment.
Darry Stuart of DWS Fleet Management, Wrentham, MA, is a TMC Silver Spark Plug award winner and an authority on preventive maintenance. Stuart says rust prevention starts with your predelivery inspection.
“Make sure the truck has been properly prepared and that everything can resist corrosion. Wash your trucks regularly. Consider painting as a part of preventive maintenance. And consider specifying stainless or composites whenever possible,” he said during a session on corrosion prevention at the 2003 SAE Truck and Bus meeting.
Electrical systems have special problems, said another TMC Silver Spark Plug winner, Brad Van Riper, Truck-Lite vice president of research and development.
Speaking at the 2004 SAE Commercial Vehicle meeting, Van Riper said, “When wiring, include drip loops so corrosive sprays don’t enter connectors. Don’t mount connectors vertically. Don’t put side loads on connectors and cover them to deflect spray.
“Use connector boots, filled with plenty of dielectric grease to form a moisture barrier, unless the plug design doesn’t allow for the grease. Some newer ones don’t because the grease forms hydraulic locks preventing good connections.
“And never splice or probe into wires and cables through insulation. Use adaptor plugs. Never violate any wire’s integrity.”
Corrosion is a major problem, but not an insurmountable one. With thorough, careful maintenance practices, by being aware of corrosion and buying equipment that is rust resistant, you can survive until the corrosion-proof truck becomes available.
Paul Abelson may be reached at firstname.lastname@example.org.