Electrolysis

Corrosion in the cooling system.

 Electrolysis: Part 3 of a Series

Dave Gordon  Director of Technical Services

Reprinted with permission. All copyrights belong to N.A.R.S.A.

How can you test for and correct electrolysis?

You stand back to admire your work. A beautifully soldered seam, a perfect repair. The radiator is reinstalled in the customer’s vehicle and they head down the road, mission accomplished. Another satisfied customer!

We now fast-forward to three months later. You’re looking at the same radiator. The beautifully soldered seam is gone. In it’s place, an open seam dripping ant-freeze. Your satisfied customer is history. What went wrong?

Let’s start at the beginning, when the customer first arrived at the shop. Did you diagnose just the leak or did you also diagnose what caused the leak?  If you had done the second step, chances are you would not be looking at a comeback.

So what caused the repaired seam to fail?  One possible answer and the subject of this portion of the series, is electrolysis.  Electrolysis occurs naturally in the cooling system. But, where does the electrical current originate? Well, just the simple act of moving your shoes around on the carpeted floor of the car produces an electric current. In addition, stray electrical current from operating systems in the vehicle and from the static charge of the vehicle itself flows through the cooling system. As the coolant flows throughout the system it develops a minor electrical charge (less than .3 volts). Once this stray electrical current finds its way into the system, it travels around  (even through the hoses) looking for a ground. When the ground is located, the electrical current is discharged, no harm done.

But what happens when there is no ground to be found, or an ungrounded electrical device in the vehicle creates excess electrical current?  The cooling system has the ability to hold large amounts of excess electrical current, which turns the coolant into an electrolyte. Any fluid that becomes electrically charged (like automotive coolant) becomes an electrolyte. If this excess current cannot be discharged by means of a ground, it continuously travels through the system, looking for a way out. During its travels, the charged coolant causes electrochemical reactions with the various surfaces it contacts. When it locates an extremely favorable material, it goes to work devouring the material completely. Think of the charged coolant as a very hungry termite. Trapped in a box made of several different kinds of wood, it travels around inside the box, looking for a way out. As it goes along, it samples the various woods. When it finds the tastiest piece, it sets about devouring that piece until it can escape. The charged coolant does much the same thing, traveling around in the cooling system, looking for that “tasty” piece. When it locates it, it “eats” its way through trying to escape. Once the material is gone and the coolant can escape the electrolysis process is over. Until the next time.

Now we know what happens and why, but are we done? We now need to take a better look at electrolysis, what it is, what it does and how to correct it before we can confidently say we are done.

Electrolysis is the passage of an electric current through a conducting solution that is decomposed in the process. When a cathode, or negative electrode, and an anode, a positive electrode, are dipped into a solution and a direct current source is connected to the electrodes, the positive ions migrate to the negative electrode and the negative ions migrate to the positive electrode. At the positive electrode each positive ion gains an electron and becomes neutral; at the negative electrode each negative ion gives up an electron and becomes neutral. The migration of ions through the electrolyte constitutes the electric current flowing from one electrode to the other. Phew! So much for the scientific definition. Lets break this down to something you can use to educate your technicians and your customers.

Lets suppose the kid with the lowered Honda comes into your shop with a leaking radiator. As you look under the hood you notice two rows of tubes with voids at the top. In addition you see where the kid has mounted his bazillion watt stereo amp to the radiator support panel. How do you explain to this kid that his stereo caused his radiator to fail. Even if the stereo system was properly grounded, the amp will use the radiator support as an additional or supplemental ground. The electrical discharge will travel directly into the coolant, charging it, there by turning it from a protective fluid into a fluid that destroys almost everything it touches. Bear in mind, it does not have to be something that is mounted or wired right to the radiator or support to cause this. I know of an instance where a pickup truck was experiencing electrolysis problems due to a faulty ground in a fifth wheel camping trailer the owner pulled. In other words, anything that is wired into the electrical system, either temporarily or permanently, can cause electrolysis in the cooling system if not properly grounded. Proper grounding can mean having to add additional grounds if necessary to control excessive voltage produced by the addition of electrical accessories.

Just what can electrolysis do to a vehicles cooling system. In one case it completely destroyed a brand new radiator in less than thirty days. This of course is the extreme. Lets focus on the more common. Electrolysis can cause material surfaces to pit and flake. Enough stray electrical current can cause solder to become flowable. In another extreme case, electrolysis caused a heater core to bulge and split. The most common effect however, is corrosion. We have all seen the white and green solder blooms in cooling systems. Ever wonder what caused them? Electrolysis is one prime candidate.

Aluminum affected by electrolysis will corrode rapidly in the form of flakes. These flakes will suspend in the cooling system and eventually build up causing system failure. Cast iron engine components will corrode, causing rust to enter the system, contaminating the coolant and allowing the system to slowly destroy it self. Soldered joints will become flowable and produce leaks. Premature part failures, overheating, cavitation of cylinders and passages, and deposit formation causing system failure are symptoms of or are caused by electrolysis. How can you test for and correct electrolysis? The test is very simple. Using a volt ohm meter (digital is preferred) connect the black or ground lead to the battery ground and lower the red or positive lead into the coolant in the radiator. Do not touch the filler neck sides or the tank. Any reading over .3 voltage is indicative of excess current entering the cooling system. Always perform this test twice, once with the engine off and all accessories off and once with the engine running and common accessories (radio, heater or A/C, lights ect.) on.

The first and most important step in the correction of electrolysis is a good visual inspection. Check all under hood wiring for loose connections or poor repairs. Look for additional accessories added by the customer for poor wiring, or missing or poor grounds. Hopefully the problem is just a poor or missing ground in the engine compartment. This is usually the problem, as many DIYers and technicians alike fail to reinstall engine ground straps. If the problem does not readily present itself, prepare for what may be a long diagnostic process. Inspect the wiring under the dash and trough out the vehicle, paying close attention to the grounds. If no bad wiring is located, have an assistant hook up an ohm/volt meter, turn every-thing off and read the voltage. If it is in acceptable limits, turn on the accessories one at a time. When you see a voltage spike, you have your culprit. Locate and fix the problem, but continue with the test to make sure there are no other electrical problems. If you record unacceptable voltage readings with everything turned off, go to the fuse panel and remove and reinstall the accessory fuses one at a time. When you get a voltage drop, note which accessory you disabled and check the wiring for that accessory.  After making necessary repairs, reinstall the fuse and check the system again. If there is no excess voltage present, the job is complete. If there is still excess voltage, continue removing and reinstalling fuses one at a time.

Electrolysis is a nuisance for cooling system professionals. It can cause a tremendous amount of damage in a short amount of time. Testing for electrolysis is very simple and should be done as a matter of course every time you perform a preventative maintenance service to a customer’s vehicle. When diagnosing electrolysis, if the cause is not readily apparent, talk to your customer and learn as much as you can about there driving habits, specifically what extra accessories they might use in the car of which you are not aware. It could save you a long drawn out diagnoses.

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