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.
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 such as your fire pump. Older fire apparatus equipped with steel booster tanks generally had several of these sacrificial anodes threaded into the lid, extending down into the water about 18 inches. Newer trucks equipped with plastic or composite tanks generally have these anodes threaded into the pump; inspect and replace them according to the manufacturer’s recommendations.
Generally most manufacturers recommend replacement at least every five years. However, I recommend inspection at earlier intervals because degradation of the anode is directly connected to the quality of the water in your area and whether your department runs a dry or wet pump as procedure.
Galvanizing is yet another way to protect and extend the life of steel from the effects of corrosion, particularly where exposure to salt is a major concern, and has been used for many years in steel boat trailers. Rosenbauer America now offers it as an option for its apparatus chassis to add another way to protect your major investment from the serious effects of corrosion.
This also brings to mind the devastation caused by Hurricane Sandy in late 2012. Many of the ERVs responding to emergency calls drove through salt water. Hopefully those units were washed carefully after things calmed down. Even with a good pressure and steam cleaning, however, salt has a way of staying in nooks and crannies and rearing its ugly corrosive head as time passes. Careful periodic inspections with an eye for tell-tale rust stains should be an order for those units that drove through salt.
Cooling and Electrical Systems
The engine cooling system in your rig can also fall victim to the damaging effects of galvanic corrosion, more commonly referred to as electrolysis in this case. Coolant that is not changed according to schedule will become acidic. When this occurs, different materials in the system (aluminum, brass, steel, and cast iron) are now connected electrically via the coolant, and the damaging process is now eating away at vital areas of your engine and cooling systems. A simple check with a digital voltmeter can alert a technician that the coolant needs to be changed. Essentially what you’re testing is the electrical conductivity of the coolant. Place the positive lead in the coolant and the negative lead on a good ground at the radiator. The engine should be running. Any reading in excess of 0.3 or 0.4 volts is not acceptable, and electrolysis can damage the cooling system.
In another example, plastic washers can also be used to separate aluminum from stainless steel to protect from the effects of galvanic corrosion. Ever notice how the area around a stainless steel bolt or screw that is contacting aluminum turns white? This is galvanic corrosion at work.
Electrical systems can also suffer from the effects of corrosion. The most common problem, if you don’t have a good PM program, is corrosion at the battery terminals. In my experience, the best way to prevent problems in this area is to keep battery tops clean from dirt and battery acid. Also, you need to ensure the terminals are cleaned properly and liberally coated with either terminal sealer or white lithium grease. I like the lithium better, and even though it might be a little messier, I think it does a better job if applied correctly.
I am sure that most reading this realize this is Maintenance 101, and you are right. However, corrosion can cause serious problems in sensitive computer circuits that can cause your ERV to break down. Remember Murphy’s Law. Corrosion at electrical terminals creates voltage drops that can ultimately cause engine, transmission, and pump failures. Corrosion in electrical connectors can cause voltage drops because of an increase in resistance. High resistance in high-current circuits can also cause electrical fires. Although most of today’s electrical connectors are considered water-tight, I have seen water get into many. Most have been because of improper installation and harnesses pulled too tightly that distort the seals in the connectors, which eventually will allow water in. It is also a good idea to use quality dielectric grease in electrical connectors that are in areas exposed to water and the elements. A thorough inspection of your ERV’s electrical system that is exposed to the elements may pinpoint some of these potential problems before they can cause a breakdown. If it is not part of your PM inspection checklist, I recommend you add it.
As I mentioned before, corrosion is a silent enemy. If left unchecked, it will work against you nonstop. It can undermine the structural integrity of components such as the frame rails of your ERV’s chassis and in doing so can cause serious safety concerns, particularly if you have an aerial device resting on the frame rails. This is one of the main reasons manufacturers use paint-to seal and protect iron and steel from rusting. It is not just for aesthetics.
Today’s modern primers and paints do a great job. However, if the surface of the material was not prepped properly, it does not matter how technologically advanced and expensive the process was. Rust can turn the chassis of your expensive ERV into dust much faster than you would think possible. If the part or component that is rusting is in an area that is not visible, severe rust will generally leave red telltale streak marks, particularly if water occasionally washes over the area-common in any ERV chassis. A good PM inspection program should go a long way toward finding these issues and at least put these problems on the radar.
Cases in Point
A fire department on the east coast of South Florida had to remove an aerial device from service that was only five years old. Corrosion seriously compromised the structural integrity of the torque box-the aerial structural platform that bolts to vehicle chassis-to the point that it could fail. Just think if this problem had not been detected when it was and the aerial failed during operation.
Whether during morning checkout, a training drill, or a fire assignment, the potential for loss of life exists and should not be ignored. In Ohio, a 100-foot aerial platform lost its rear axle when the U-bolts failed because of corrosion. Nobody noticed that the U-bolts were severely eaten away by corrosion. Luckily nobody got hurt. Yet another item that came to light while I wrote this article is the fact that the new diesel emission fluid (DEF) is highly corrosive, so it would behoove maintenance organizations to look for leaks in the system that could cause corrosion to the chassis and other vital undercarriage components.
Brakes are another safety area that can be severely affected by corrosion. Rust jacking is the term given to drum brake linings when they are lifted off the shoe because of corrosion between the brake lining and the metal shoe. Although this occurs mainly in areas where road salt is used, all technicians should carefully inspect for any signs of this issue to prevent failure of the brake linings. Needless to say, failure in this area can lead to total brake failure.
I can cite many other examples. However, I think you get the point. Train your technicians to keep a watchful eye out for these silent enemies that can take your rig out of service; cause considerable downtime; and, more importantly, threaten the safe operation of your ERV. Remember another old adage: An ounce of prevention is worth a pound of cure.
CHRISTIAN P. KOOP is the fleet manager for the Miami-Dade (FL) Fire Department. He has been involved in the repair and maintenance of autos, heavy equipment, and emergency response vehicles for the past 35 years. He has an associate degree from Central Texas College and a bachelor’s degree in public administration from Barry University and has taken course work in basic and digital electronics. He is an ASE-certified master auto/heavy truck technician and master EVT apparatus and ambulance technician. He is a member of the board of directors of EVTCC and FFMA and a technical committee member for NFPA 1071, Standard for Emergency Vehicle Technician Professional Qualifications.