Are you aware of the hidden menace that is attacking the inside and outside of your buses and fleet vehicles? The “salt age” is dawning in North America, and road salts are creating an epidemic corrosion problem for America’s transit systems. The U.S. Federal Highway Administration released a two-year study on the direct costs of metallic corrosion, “Corrosion Cost and Preventive Strategies in the United States.” This study estimated that $6.45 billion is spent on corrosion-related repairs and maintenance in the transportation industry. As an industry, suppliers and transit systems are trying a number of approaches to address corrosion-related problems. One method to control corrosion caused by road salts is to integrate the proper wash systems and detergent technology into routine cleaning of buses.
For several years now, transportation-related industries have been concerned about the corrosive effects of road salt. The American Trucking Association’s Technology and Maintenance Council (TMC) has established a Corrosion Action Control Committee to investigate and propose solutions for corrosion-related problems. During the TMC Fall Conference, a number of speakers spoke about the extent of the corrosion problem in the trucking industry. The magnitude of corrosion-related problems is astounding. Corrosive road salts attack a variety of metal components to include frame rails, crossmembers, suspension components, air tanks, fuel tanks, battery boxes, brackets, brake shoes, electrical systems, air-conditioning condensers, radiators, metal coolant tubing and steel wheels. It stands to reason that road salt corrosion is a problem for all vehicles that share the road.
The harmful effects of road salts
In order to maintain open highways and increase highway safety, the northern tier of the United States has used salt (sodium chloride) for years to combat ice, snow and sleet. Over the last decade, many state highway departments have switched to the more effective calcium chloride (CaCl2) and magnesium chloride (MgCl2) deicers because they provide lower freeze points, are less expensive, less corrosive to concrete and less harmful to the environment. However, the use of these additional road salts has resulted in a major increase in vehicle corrosion, particularly the underbody and electronics of buses and other fleet vehicles.
The sodium, calcium and magnesium chloride salts lower freeze points of water to keep highway surfaces wet and slushy rather than icy. Magnesium and calcium chloride are much more effective deicers because they stay liquid at a much lower temperature and less material is required to melt the same amount of snow and ice. Many state DOTs are now spraying calcium and magnesium chloride solutions on the roads prior to and after winter storms. These deicers are often mixed with sugar beet juice or vegetable oils for better adhesion to the road surface. While the roads are safer, the deicer cocktail, sand and traditional road grime create more difficult vehicle cleaning conditions.
While these antifreeze salts are water soluble for deicing applications, the calcium and magnesium chlorides get quite viscous as water evaporates, collecting sand and dirt and form compacted deposits in recessed areas. These difficult-to-remove deposits are the source of major chloride corrosion. To complicate the situation further, if the road salts are not removed from the vehicle, MgCl2 and CaCl2 will pull moisture out of the atmosphere, rewet and continue their corrosive actions.
What is the effect of road salt on the typical transit bus?
Corrosion associated with winter deicers is becoming a multimillion-dollar headache for the transit industry. In an era of tight budgets, a transit bus is expected to last for 12 to 15 years, but corrosion can significantly shorten the useful life of a bus. From an exterior viewpoint, road salts immediately mar the appearance of a bus until it can be washed and contribute to exterior surface pitting/rust spots. If not completely removed, road salt residue may affect the quality of advertisement imagery on bus exteriors.