Death by Electrocution

 What is Electrolysis

Also commonly called Stray Current corrosion; it's the systematic removal of the protective layer on the inside of the radiator tubes and other components. It is a killer of cooling system components usually is quite localized and in severe cases will destroy radiators and heaters in weeks.

 Death by Electrocution


Electrolysis is seldom found in new vehicles but more often than not when aftermarket accessories have been fitted, or the vehicle has had major engine repairs or been in a collision and earth straps have not been reinstalled or they have been attached to a freshly painted area that prevents a positive ground or earth. On occasions it's also caused by a fault in the wiring loom.


                   Core as it was when fitted                                  Tubes corroded by electrolsis in 3 weeks


There is a systematic removal of the corrosion protection layer on the inside of the radiator tubes. This will cause the tubes and header plate to corrode resulting in multiple holes in this area. The residue from the corrosion can often be seen through the outlets and this residue will begin to clog the tubes.


Today's vehicles have a jungle of wires and electrical components, and have many accessories fitted (GPS, new stereo's, phones etc)so a electrolysis test should be carried out whenever there has been a disruption to the electrical system or accessories fitted, and any time a radiator or heater is replaced.

 How To Test For Electrolysis

Use an Analogue Multi-Meter or a dedicated Electrolysis Tester.

1.  Remove the radiator cap from the vehicle when safe to do so.
2.  Turn your multi-meter to mV range and insert the positive lead into the coolant (be sure not to touch the metal or plastic radiator tank or header plate) 
3.  Connect the negative lead of your multi meter to the earth terminal on your battery.
4.  Check your multi-meter for a reading above 50 mV, any reading above 50mV is corrosive.
5.  Turn on all the vehicle accessories including indicators, lights, heater, electric fans, wipers, radio, phone charger and even brake lights. 
You will be able to trace the likely fault by seeing the changed reading on your multi-meter as you switch items on or off.


Blackening of the header plates
The tube and brazed joints have corroded away

Top header plate discoloured


Evidence of aluminium oxide residue 
settle inside the tank


Q.  Does Electrolysis just effect aluminium radiators and heaters
A.  No it is also found in copper brass systems but copper and brass are able to resist the corrosion for a far longer time.

Q.  Why does Electrolysis attack localized area's or parts.

A.  The electrical current travels though the coolant looking for an earth and generally will attack the path of least resistance,which are often new radiators and heaters that have just been fitted.

Q.  Is there anything I can do to avoid Electrolysis.

A.  Ask your vehicle service provider or qualified radiator specialist to test your vehicle when being serviced. 
Your vehicle should always be tested immediately after any electrical work has been undertaken or your radiator or heater core has been replaced.

Don't get caught out!

Please feel free to phone Graham Stevens with any question you have or for any further details you require.