Metal Shop: Electrolysis and Grounding 101
Replacing a crunched radiator is an everyday occurrence in most body shops. What you may not know is the extent of problems your technicians and mechanical repair staff can cause if they are oblivious to the impact of proper grounding and ultimately electrolysis. Failing to discover and replace one torn ground wire can precipitate a very serious radiator and/or heater degradation problem for unsuspecting customers.
You may be familiar with the term electrolysis as it relates to the destruction of hair roots with an electric current. In the automotive world, electrolysis can cause hair pulling by service technicians who are unable to diagnose the root problem.
Although electrolysis is a somewhat complex electromechanical reaction involving anodes, cathodes and Faraday's laws, you don't need to make a run for the chemistry textbooks or the Internet. In simple terms, electrolysis in a radiator or heater is the localized degradation of the metal caused by excess electrical current flowing through the cooling system's liquid coolant or metal transmission lines in search of an electrical ground. But what happens when there is no ground to be found, or an ungrounded electrical device in the vehicle creates excess electrical current'
Electrical current can be introduced into the cooling system in many ways, but some common causes are loss of ground due to mechanical damage or corrosion, or a frayed electrical wire coming in contact with the radiator. Any vehicle with accessories (such as driving lights) using the radiator as a ground is begging for an electrolysis problem. For body shop personnel, failing to see or detect a ripped ground wire or forgetting to replace one or more ground wires can cause electrolysis that won't show up until months after your customer has left your shop with a repaired vehicle. Proper grounding is the key to avoiding the occurrence of electrolysis and, should it occur, grounding can be the key to diagnosing the root cause.
The evolution of grounding in the automotive industry is tied to the revolution in electronics. In the not-too-distant past, grounding was a simple concept that applied to the ignition system, the starting system and the auxiliary system for lights, an AM/FM/8-track radio, heater, etc. Before the days of front-wheel drive and transverse-mounted engines, cooling system electrolysis was a rare occurrence. But today, with most cars, vans, light trucks and SUVs featuring electric cooling fans in conjunction with ungrounded plastic-tank radiators, cooling system electrolysis is becoming a more frequent problem.
Electronics may top 50 percent
Spurred on by efforts to achieve differentiation through comfort and convenience features, vehicle manufacturers are replacing electromechanical linkages with pulses on wires at a frenzied pace. According to industry supplier AVX Corporation, the electronic content of vehicles during the 2004 model year reached 35 percent of total cost. Projecting the recent annual growth rate of 16 percent, electronic content is on a pace to top 47 percent of costs during the 2007 model year. Even at a slower growth rate, it's not inconceivable to forecast that electronics will top 50 percent of vehicle content costs within five years.
Fuel systems are just one example of the accelerating evolution of recent years. The conventional carburetor with mechanical linkage first added electric solenoids and then was supplanted by electronically assisted throttle-body fuel injection. Although mechanical fuel injection was applied sparingly, electronic fuel injection has quickly become the industry norm. NASCAR's preference for conventional carburetors is one of the few remaining strongholds. Extending the 'fly-by-wire' trend started in the aerospace industry, the term 'drive-by-wire' is now commonplace among automotive engineers, technicians and, increasingly, the motoring public.
The first waves of the electronic revolution transformed under-hood and under-dash technologies. Although their impact wasn't always readily apparent to the motoring public, the appetite for convenience gadgets has grown exponentially in recent years. The long and rapidly growing list includes phones, DVD modules, satellite audio systems, entertainment centers, powered doors and lift gates, GPS navigational systems and Internet connectivity. Beyond the basics for seatbelts, door and ignition keys, a plethora of new sensors for everything from ABS brake systems to tire pressures and seat positions, steering wheel angle and brake pedal location have hit the marketplace.
Grounding more important than ever
No doubt, the installation of additional electrical systems, components, microprocessors, sensors, electric motors, electronic convenience items and related circuitry has placed an added burden on the automotive service industry in general and body shops specifically. Although microprocessors are capable of providing feedback through self-diagnostics, they have limitations. That means service technicians need various scan tools and electronic meters to receive the two-way communication that today's electronic components provide. Having the tools is one thing. Understanding the concepts and interpreting the readings are critical to successful diagnostics.
In spite of the electronic revolution sweeping the industry, one basic tenant remains unchanged. To complete the flow of electricity, the negative circuitry emanating from the battery must be properly grounded. Almost without exception, the frame and/or body sheet metal serve as the primary grounding device for the electrical system. If properly connected, it is in fact an extension of the battery negative connection. Although the body is typically isolated from the chassis by non-conductive, cushioned insulators, the many supplemental ground wires connected to each vehicle body are connected back to the chassis and the battery by one or more body-to-frame jumper wires.
While the vehicles of yesteryear may have had just a few ground wires, it is quite common to have between 10 and 20 chassis-ground connections sharing the load today. Each must be functioning properly to complete the circuit and route the flow of electricity back to the battery. Any broken, loose or corroded connections are almost sure to cause a malfunction and/or alter the flow of electricity. Because it takes the path of least resistance, electrical current will stray from its intended route and create a return flow by looking elsewhere.
Be suspicious of ground wires
Damage to ground wires is almost inevitable, even during a moderate collision causing $3,000 to $7,000 in damage. During the repair process, be sure to check your collision repair reference to make sure you know the location and connection points for all ground wires. When they are securely connected, the electrical path is well defined. On the other hand, any breach will cause the electricity to find the shortest, easiest, quickest path of least resistance. Particularly for electrical components or circuitry in close proximity to the radiator or heater'that path can involve the coolant itself.
If you have the occasion to check for electrolysis, use a digital voltmeter set for 12 volts. Attach one test lead to the negative battery post and insert the other test lead into the radiator's coolant, making sure the lead does not touch the filler neck or the core. Initially, you may see a surface charge that could be 0.7 volts or higher. It could take up to two minutes for this surface charge to dissipate. Only then will you be able to obtain an accurate reading. A voltage reading of 0.3 or higher indicates that stray current is finding its path to ground through the cooling system.
Cooling fans and A/C-heater fans are logical sources to check and eliminate early in your diagnostic process. Then check any non-factory accessories that have been added. Next, you can turn the ignition to the run position while turning various accessories on and off. When the meter's voltage jumps, you've found the circuit with a bad ground. A small amount of electricity normally flows through a vehicle's cooling system. In a properly grounded system, this small charge (less than 0.3V) is constantly discharged and no harm is done.
Serious problems with stray-current electrolysis can occur when the cooling system is not grounded or when an ungrounded electrical device is part of the vehicle's operating system. The cooling system then becomes a warehouse for this stray electricity, and the coolant turns into an electrolyte. This charged coolant is constantly searching for a ground or a way out of the system. When it finds a material it can attack (the path of least resistance), the coolant goes to work 'eating through' that material radiator and/or heater causing damage such as the following:
Stray current also can be a problem with new, straight-from-the-factory vehicles. Back in 1986, Ford recalled approximately 19,400 vehicles to find a misrouted battery cable that could send a low-grade electrical current through the radiator, setting up an electrolytic action that could promptly ruin the radiator.
Frequently, by the time your customer realizes electrolysis is taking place, the radiator or heater damage is already done. Unlike a radio that frequently hums when a short exists or a resistor malfunctions, the cooling system does not emit an audible sound. To make sure that electrolysis doesn't start in your shop, let your technicians know the importance of reconnecting all ground wires.
What the future holds
For sure, you and your technicians will see more, increasingly complex electrical components and circuits in the vehicles that are brought to your shop for collision repair. As the price of mass-produced technology declines and consumer demand for convenience increases, the world of the possible will continue coming to the automotive industry. Many other ideas that are common in the aerospace industry remain to be transferred to automotive applications.
Soon water pumps will be electrically driven. Hybrid electric cars are already here. Battery-powered vehicles are on the horizon. These vehicles already operate at higher voltages and carry warnings about possible electrocution. A near-term change using existing technology is the 42V electrical system. Any electrolysis problems are likely to be the same, but the higher voltage is a good bet to cause larger and/or faster problems.
Tune in to new developments and stay current with diagnostic tools and procedures. Proper electrical grounding is just one of the many facets of collision repair that you need to know. Lack of knowledge is no ground for returning your customers' vehicles with incomplete repairs and easily avoided radiator and/or heater failures caused by electrolysis.