Since the early years of salt (sodium chloride) use for de-icing roadways in the 1930s, the chief challenge of winter maintenance, mobility and safety has been the never-ending quest of finding the ideal de-icer. As ice management chemicals change, so do the corrosion effects on vehicles and equipment.
In the late 1990s, the winter road maintenance strategy of anti-icing began to take hold in the U.S. and Canada as a way to prevent or minimize the bond between snow or ice and the pavement surface from forming. Anti-icing involves applying ice control chemicals before or at the very beginning of a storm. These typically are liquid chemical applications of salt, magnesium chloride, calcium chloride, calcium magnesium acetate and potassium acetate, with magnesium chloride and calcium chloride being the more popular choices.
Because anti-icing chemicals are applied prior to snow or ice fall, the probability of exposure to vehicles is increased. These materials are especially destructive because of their ability to cling to the underbody of a vehicle and re-crystallize as they slowly dry out. By their very nature, anti-icing chemicals attract and absorb moisture from the surrounding environment, keeping them in a semi-solution state for extended periods of time, which multiplies their corrosiveness.
De-icing chemicals and road salts don't melt snow or ice. Rather, they lower the freezing point of water by creating a brine solution.
Aggressive corrosion on vehicles caused by various formulations of road ice clearing chemicals has been a serious maintenance problem for many equipment users for more than 10 years, points out Robert Braswell, technical director of Technology & Maintenance Council (TMC), North America's premier technical society for truck equipment technology and maintenance professionals.
"It's widely known among fleet managers that use of magnesium chloride- and calcium chloride-based products by certain states is especially associated with increased incidence of corrosion on vehicles, causing damage in as little as a single winter season," he says. "As early as 1999, reports of this problem have manifested themselves through frame corrosion, brake table rust-jacking and excessive wheel and wheel fastener rust."
Corrosion of metals reduces the useful life of any vehicle, resulting in increased costs and decreased uptime. It is imperative to catch corrosion as soon as possible. Like a form of cancer, corrosion takes a certain period of time to manifest itself and can spread undetected until damage becomes significant. However, corrosion can be treated and repaired if caught early and the proper measures are taken.
In order to prevent vehicle corrosion, it is necessary to understand what corrosion is. Basically, corrosion is defined as the degradation of a material by reaction with its environment. Degradation implies deterioration of physical properties of the material.
Corrosion is derived from the Latin word "corrodere," meaning to eat away. The most common form of corrosion is called rust.
"Corrosion is an erosion or deterioration of a metal surface caused by an oxidation from a chemical reaction," says Matt Murray of Eastwood Company, a producer of auto repair and restoration supplies. "If you keep in mind how erosion comes into play with sand and the ocean at the beach, it is easier to understand. The chemical reaction actually makes the metal fall apart or ‘erode' away. This is especially an issue when it comes to structural points of a vehicle."
Road salt or de-icers can speed up the chemical reaction between iron and water, which causes rust or corrosion, thus making a bare metal area much more vulnerable to rust damage.
"Salt can promote corrosion on most any types of metal. The longer it is stuck on a metal surface - even if in a watered down film state, the quicker the surface will degenerate or corrode," says Murray.