STRAY CURRENT & ELECTROLYSIS

What is it ?

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.

What will it do?

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.

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.

How do i eliminate of it?

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 for poor wiring, or missing or poor earths. Hopefully the problem is just a poor or missing earth in the engine bay area, This is usually the problem, as many repairers fail to reinstall engine earth straps after repairs.

If the problem does not readily present itself, prepare for what may be a long diagnostic process. Inspect the wiring under the dash areas and any other areas where wiring is located, paying close attention to the earths. 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 regularly.