Electrolytic corrosion

Engines and Engine Systems
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mike.hughes
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Electrolytic corrosion

Post by mike.hughes » 22 Mar 2013 09:45

Greetings to all, I wonder if someone could possibly shed some light on the following: I own a Patrol 4.2 petrol and last week when I started her she had a severe misfire, I then discovered that the head gasket had in fact blown!! I can assure you that in no way at all did the car overheat. I towed the vehicle in to the garage whom I have been dealing with for some time now and they removed the head told me it was corrosion due to age and sent it to the engineers for further work. The engine has less than 150 000 kms. I spoke to the man in charge at the engineers and he informed me that the damage was due to electrolytic corrosion. I replaced my radiator in Dec 2012 with a brand new copper/brass radiator (half the price of the aluminium radiator from the agents). I have been told that because there was no earth strap between radiator and the negative of the battery this would cause severe corrosion as copper and aluminium are not friends. Please could someone shed some light on this matter because if it is indeed the fault of the mechanic who never installed an earth strap then I would like to take the matter further.
Thanks in advance
Mike

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Re: Electrolytic corrosion

Post by Carel » 22 Mar 2013 13:22

Mike. I went to a spares shop last week and saw a notice stating something of that effect when fitting a new radiator you must make sure of an earth strap, if it is not fitted the gaurantee might be void. So yes there must be some truth in it.
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Re: Electrolytic corrosion

Post by ricster » 22 Mar 2013 16:22

hey???.... I've never heard this before.... I'm very interested and am going to follow this....
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Re: Electrolytic corrosion

Post by Tinus lotz » 23 Mar 2013 08:36

On electrical lines ect you can never connect ali and copper with one another there are a cemical reaction between the 2

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Re: Electrolytic corrosion

Post by caz » 30 Mar 2013 11:50

Hi Mike, The original radiator is rubber mounted. If a reputable workshop fitted a copper radiator they should have fitted two earth straps, one to the battery and one to the engine block or at least have informed you of the potential hazzard. Also the anti freeze should have been mixed with distilled water and not tap water. As a precaution the workshop should have done a voltage check with a multi meter, with the vehicle warm place the neg probe on the battery neg and the positive probe in the radiator water. The reading should be less than 300 mili volts . This check should be done every 3 years to check the condition of the anti freeze. Seems they built in a time bomb for you if you ask me. I just checked my 4.5 Patrol and the reading is zero. Rgds Caz

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Re: Electrolytic corrosion

Post by mike.hughes » 30 Mar 2013 20:17

Hi Caz
Thanks for the tips, my story however gets worse, I went to the garage on Thursday to collect my car and sure enough the radiator is rubber mounted as though it was the plastic/aluminium one, no earth strap to be seen , I did the voltage test in front of the staff and guess what? not 0.003 or even 0.010 but a whopping 0.35 volts!!!!! needless to say they where speechless, I then fitted a temporary earth strap which they provided and immediately the voltage dropped to 0.10 volts. Furthermore the garage managed to break off my temp. sensor and turn off an exhaust stud....I'm taking this saga up again on Tuesday.

I'll keep you posted

Mike

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Re: Electrolytic corrosion

Post by caz » 30 Mar 2013 20:52

Mike what you have with those readings is Galvanic corrosion, this happens when two dissimilar metals are placed in electrical contact in an electrolyte. If tap water was used or even mixed with the anti freeze this will allow a small current to flow from the anode ( aluminium head ) to the cathode ( copper radiator ) What happens is the aluminium disolves in the coolant and is deposited onto the copper. This goes on 24/7 and will eat that head in a matter of months. You have to get that reading below 300 mili volts. Suggest you change the coolant with a mix of anti freeze and distilled water and check all the earth straps are making good contact.

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Re: Electrolytic corrosion

Post by davidvdm » 31 Mar 2013 09:52

This is very interesting. On my Skyline (petrol engine) and my Sani (diesel), I have had water pumps go on me. On inspection both showed pitting around the impeller as if they were spark eroded. The skyline water pump was so bad that when I poked at it with a screw driver, it ended up in a hole through the casing.

In both cases this was not actually the cause of the failure, but has been a concern in the back of my mind. This is the first information I have found confirming this.

I am now also interested to see what my voltage reading is as I use normal tap water and antifreeze, but don’t ask me what type of radiator I have, I am presuming it is an aluminium unit.

Thanks for the thread and information so far.
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Re: Electrolytic corrosion

Post by caz » 31 Mar 2013 10:41

Hi David, the pitting you describe is the result of electrolytic corrosion on a smal scale. For sure change the coolant to a mix of distilled water and anti freeze and this should be done about every three years or so. . Tap water contains minerals which act as an electrolyte . You really need an inert mix which prevents the flow of current. What Mike had with .35 volts was a basic battery, two dissimilar metals in a solution and the aluminium head was been sacrificed. All outboard engines all have a piece of zinc bolted to them that corrodes away before the aluminium on the motor and this is called the sacrificial anode...... The guys fitting LS chev motors and maybe custom made copper radiators had better take note. Those are aluminium motors and there is a real danger if the mix is not right and not properly earthed. Rgds Caz

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Re: Electrolytic corrosion

Post by Michael » 24 Nov 2015 08:22

Interesting topic and I want to bring it back to life as I have some corrosion issues on my Patrol at the moment. This happened way before I had it, so just reading up on the net what I am going to do as I have a copper radiator.

I found this website that was very interesting and factual
http://www.super7thheaven.co.uk/blog/al ... corrosion/

In summery it sais the following:
*Fresh Anti-freeze and clean water is important
*Replace your thermostat regularly
*Anti-freeze needs changing regularly – especially with aluminium radiators
*Engine, Chassis and Bodywork grounds protect your radiator
*DO NOT GROUND YOUR RADIATOR!
*Rubber mount and electrically insulate your radiator
*Aluminium Radiators are more susceptible to damage
*When batteries are are several feet away from the engine; e.g. in the boot; then the size of cables needs to be upgraded and particular attention paid to chassis and bodywork grounds.
*Don’t mount your fan directly to the radiator (especially with cable ties)
*Rubber mounts protect damage from vibration (a big problem for aluminium radiators)
*Plastic fan housings are good for absorbing vibration and electrical insulation
*Disconnect the battery and drain the radiator when vehicle is in storage
*Where possible, fit a fan shroud
*All of the above applies to the cars heater / demister
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