By Christian P. Koop

Most of us in the emergency response vehicle (ERV) service and repair industry generally do not give much thought to the effects of corrosion (rust, oxidation)-at least not to the degree I think we should. I believe it is one of those things that is not really at the forefront of a maintenance organization's hit list. Usually when you find it is a problem it is kind of late, and the cost to correct the damage can be great. I am not just talking about cosmetic items such as body rust and corrosion. There are a number of important areas that, when left unchecked, can lead to serious safety issues or cause your ERV to break down.

If you have been around this field a long time, you have probably learned that breakdowns usually occur at the most inopportune times, such as when your pumper is on a third-alarm fire and the engine shuts down or your rescue/ambulance breaks down during a patient transport. This is classic Murphy's Law at work. I like to refer to corrosion as the silent enemy-kind of like the termites of aluminum, steel, and electrical systems. This article explains what corrosion really is, the serious damage it can cause, and what you can do to find it and prevent it from continuing along its costly and sometimes deadly path of destruction.

Affects More than Metal

Corrosion is a process that can affect most metals but can also affect other materials, such as ceramics or polymers. It is a gradual process that will totally destroy these materials because of a chemical reaction with the elements that surround it. When the material is metal, what occurs is electrochemical oxidation reacting to oxygen. This process is more commonly referred to as oxidation.

Most people are familiar with the term "rusting" and the reddish brown colors that become more and more visible as the process accelerates. This is the most common form of corrosion in metals that contain iron and in various alloys that are derived from it such as steel. Rust, or rusting, is the formation of iron oxides and is an example of electrochemical corrosion. Essentially what is occurring is an electrochemical transfer of electrons from the iron to oxygen. This electrochemical reaction is relatively slow. However, when salt and water are introduced, the process speeds up and can weaken and destroy substantially large steel structures faster than you would think possible. Think about structural components, such as the ERV's chassis. If equipped with an aerial device, the structural integrity of the chassis plays a critical role in the stability of the entire aerial device. Train your technicians to watch for any signs of rust or rust stains. If it is not an item on your preventive maintenance (PM) inspection sheet, consider adding it. You know the old adage: out of sight, out of mind.

The other phenomenon similar to corrosion that can wreak havoc on critical areas of your ERV is known as galvanic corrosion. This occurs when two different metals are in physical or electrical contact with each other and are exposed to air, moisture or water or even totally immersed in water. The water, when exposed to air and its natural components, will essentially become an electrolyte, which will serve as an electrical bridge to accelerate removal of material from the less noble of the metals. When salt, air, or road salt is introduced in the mix, it accelerates this electrochemical reaction. This process is very similar to electrolysis, and sometimes galvanic corrosion is referred to as electrolysis.

Protecting Components

There are ways to protect components from this phenomenon. Sacrificial anodes can be used, and various alloys are used in the construction of anodes, with zinc being a very common one. These are very common in the marine industry, and normally they are referred to as zincs. They have a very important job-protecting costly key components su

Alan M. Petrillo

Auxiliary power units (APUs)-small diesel engine and generator combinations that have been used for years on airliners, locomotives, and over-the-road trucks to handle electrical, heating, and air-conditioning while the vehicle is stationary-are making more frequent appearances in fire apparatus.

Manufacturers using APUs on fire vehicles say they are responding to requests from fire departments for ways to cut down on main engine idling time, saving fuel and reducing regeneration time.

Green Edge

Scott Oyen, vice president of sales for Rosenbauer, says his company introduced its Green Star idle reduction technology nearly three years ago, which can be incorporated into any vehicle Rosenbauer makes.

"The basis of the Green Star is in the electronics, where we take a diesel-driven generator and add the intelligence of electronics to turn the unit into a fuel saver," Oyen says. "Our diesel APU is designed to provide heating, air-conditioning, and 12- and 120-volt electrical while the vehicle's main chassis engine is shut off."

Donley Frederickson, Rosenbauer's national sales manager, points out, "Today's fire service is a constantly changing community organization where we've seen the role of fire departments take on more responsibilities for medical calls, rescues, and hazmat incidents, for example. Eighty percent of calls fire departments respond to result in fire apparatus needlessly idling for between 10 and 40 minutes per call."

(1) Rosenbauer offers an auxiliary power unit (APU) on its apparatus, controlled by its Green Star electronic technology and powered by a Kubota diesel engine. (Photo courtesy of Rosenbauer.)

Frederickson notes that engine manufacturers say a big block diesel engine uses a minimum of one gallon of fuel per hour of idling. An eight-kW diesel generator APU, he says, uses approximately one quart of fuel per hour while operating under a full load. He adds that an idling main engine puts more unspent diesel soot that occurs while the engine operates at cooler temperatures into the vehicle's diesel particulate filter (DPF). "While the APU doesn't alter the chemical makeup of diesel emissions," he says, "it does reduce the amount of nitrogen oxides (NOx) that are released overall."

Oyen notes that an APU can run off of many different fuels, but Rosenbauer chose diesel so its Green Star APU would run off the vehicle's chassis fuel tank. Besides the diesel-driven APU, Rosenbauer also makes two battery versions, called Smart Batteries-one sized to provide 12-volt power on a scene for warning and compartment lighting through lithium-ion batteries and another using Smart Technology lithium-polymer batteries that can power all lighting, including scene lighting, and some 120-volt usage on a vehicle.

"An APU can replace a vehicle's generator," Oyen says. "For instance, the Tacoma (WA) Fire Department doesn't put generators on its apparatus but rather uses Smart Batteries to run all their lighting needs," he says.

Green Star features fully integrated automatic engine controls, Oyen says, where an apparatus operator can have a hands-free system activation that automatically starts the APU and shuts down the main engine. If needed, he notes, the controls will restart the main chassis engine to prevent a low-voltage situation. Green Star can be operated in either automatic or manual modes.

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