Since the decade of the 1970’s fire apparatus manufacturers have sought ways to minimize rust and corrosion on custom cabs and bodies. Aluminum and stainless steel body construction have reduced the visible corrosion however areas of the vehicle are still subject to damage from road salts and chemicals. Today it is rare to look at a fifteen year old apparatus and see extensive body corrosion due the improved construction methods, use of dielectric isolators between dissimilar materials and paint finishes. However, when you perform an inspection of the chassis frame rails and components you may find extensive corrosion on these steel components.
Over the past few years both state and local highway departments have begun using magnesium chloride, brine and other chemicals to pre-treat the roadways and salt materials during winter storms. Depending upon where you live these deicing procedures will make the roadway surfaces safer at the potential expense of coating the underside of your apparatus with these corrosive compounds.
There are several measures that your department can undertake to mitigate the effects of chemical road treatments but like any preventative maintenance they must be accomplished on a regular basis. First your department should conduct at least a monthly inspection of the chassis frame and components to clean any obvious areas of residual road salt and debris particularly during the winter months. At least twice a year the underside of the chassis should be steam cleaned of all accumulated debris.
There are several chemical additives that can be mixed into the water to achieve some degree of protection against salt infiltration into mounting surfaces between cross members and the frame rails as well as in between the frame flanges on double frame units. Your maintenance personnel should contact the fleet supervisor from the local highway department to inquire about any particular product or treatment that they utilize to protect their snow plow equipment.
When developing specifications for new apparatus consideration should be given to having the chassis frame rails, cross members and components finish painted to provide a protective layer of paint on all surfaces. Some departments require that the chassis frame and underside of the body be undercoated after assembly. While list provides protection against some corrosion the undercoating makes visual inspection of these components and subsequent maintenance more difficult.
Some apparatus builders are offering galvanized frame rails and protective coatings to minimize rust and corrosion in these areas. The apparatus committee should inquire about any process that is available along with the warranty provisions which may enhance the longevity of the apparatus. When reading through the standard cab and body structural warranties they typically cover structural defects or major failure as well as rust through body damage. With the extensive use of aluminum and stainless steel body materials it is unlikely that a rust through condition would occur under normal operating conditions.
Routine inspection and cleaning of the chassis frame and components will insure that these critical areas will provide the life cycle required for the apparatus.
Captions for Rust and Corrosion Article: All images by Tom W. Shand
Photo #1: These finish painted frame rails are on a seventeen year old pumper with some corrosion damage in areas where water was trapped inside of the split loom.
Photo #2: This is an example of untreated steel frame rails on a seven year old pumper. Extensive damage was noted on all frame rail mounted components including air reservoirs and diesel fuel tank.
Photo #3: Front bumper support brackets are heavily rusted on this four year old rescue engine. Well written specifications addressing these areas can avoid these issues during the vehicles life cycle.
Photo #4: Air reservoirs equipped with manual petcocks are susceptible to damage from road salt and chemicals. Consider specifying finish paint with stainless steel straps and hardware to minimize corrosion damage to these components.