Stray current corrosion

[rustyvit]

Any one here have any real time experience with stray current corrosion in radiators? I have just got 3 months and 3500 km's out of a new ally core radiator before it sprung a leak. The supplier is adamant that the cause is stray current, even loaning me his tester which did show current at operating temp. After reading that a fresh coolant refill can generate current for up to 12 hours I thought I would leave it until tomorrow to test it again with a multi meter.

Only god knows how many radiators I have fitted to cars over the years and although I have heard of it, never experienced it myself. Nothing unusual about the install 3 months ago, ran a cleaner through it, then flush, new radiator, all hoses and coolant. Radiator rubber mounts are all good and there is no metal contact at all.

By coincidence or not, just before the new radiator, I had the heater core leak all over the floor, which has got me wondering if that was related.

2001 Courier TD

[CRUZAAMAD]

Boss had a dual cab rodeo
maybe 98model v6

Plastic tank.. top and bottom
radiator guy said it was stray current..
mostly from the radiator

[date]

Check the voltage difference between the engine block and the battery earth terminal and also the radiator metal. I would expect maybe 100 mV difference between the radiator and the engine block. If you get minimal difference between the radiator and the block, you have an electrical connection somewhere.

[rustyvit]

Check the voltage difference between the engine block and the battery earth terminal and also the radiator metal. I would expect maybe 100 mV difference between the radiator and the engine block. If you get minimal difference between the radiator and the block, you have an electrical connection somewhere.

Across battery terminals the reading is 13.27v, battery to engine block the same voltage.
Battery earth to radiator coolant reads 0.47v
With battery disconnected, engine block to radiator coolant is still 0.47 which is confusing me.

[DamTriton]

With battery disconnected, engine block to radiator coolant is still 0.47 which is confusing me.

two dissimilar metals (iron, aluminium) and an ionic solution connecting them, with your meter across both metals = a battery.

[rustyvit]

With battery disconnected, engine block to radiator coolant is still 0.47 which is confusing me.

two dissimilar metals (iron, aluminium) and an ionic solution connecting them, with your meter across both metals = a battery.

Which confuses the issue of searching for stray current when with power source isolated I'm still getting 300mv running through the cooling system

[date]

Not much help to you, but with 0.47 V between the aluminium radiator and the cast iron block, I would say that there isn't any electrical coupling there - and that is how it should be. In fact, I was expecting lower voltage - more like 250 mV. Maybe when the engine is running, you are getting some random electrical contact due to a bit of vibration. Check the radiator to engine block voltage and also the engine block to battery earth voltages with the engine running and see if they differ from what you have measured.

[rustyvit]

I started from scratch today, drained new coolant, put an alkaline flush through the system, thorough flush and refill with demineralised water.
I think it is now worse, and the cooling system still holds .79v with the battery removed. The cooling system is generating current and it's doing my head in.


Engine running:
Battery voltage 14.47v
Battery + to block 14.48v
Battery neg to radiator water .79v
block to radiator water .79v
Battery- to radiator core - .093v (negative voltage)
Block to radiator core -.090v (negative voltage)

[date]

The fact that you now have a higher voltage differential is good. If the differential was low, you would have leakage current somewhere. I am surprised at the level of the voltage, but if the difference is going up, to me it means more resistance to earth and this is a good thing. The voltage is generated by the difference in galvanic potential of the metals used throughout the car. All the coolant does is to provide an electrical path for current to flow. You need an earth or external path to complete the electrical circuit and get current to flow. This the last thing you want, hence they mount the radiator on insulated mounts to prevent any return electrical path from being developed.

It is possible that you have a stray 12V connection somewhere onto the cooling system (maybe the temperature gauge or an engine watchdog alarm?) and that is leaking current into the system, but even then I would hope that the insulated mounts on your radiator would prevent any stray currents from going through the core. If you want to rule this out, disconnect the earth on your battery and then make the measurements. It the voltage difference drops with no battery, you do have a leak and a problem.


Out of curiosity, I checked my NW Pajero and my wife's ZJ Outlander. Pajero = 245 mV between radiator and battery earth, 244 mV radiator to car body earth. Outlander was 447 mV radiator core to body earth. Both of these vehicles were first registered 2 years ago. Both these vehicles have aluminium cored radiators. The Pajero has a Cast Iron block & alloy head, the Outlander has (I think) similar arrangement.

[rustyvit]

[quote="date"

It is possible that you have a stray 12V connection somewhere onto the cooling system (maybe the temperature gauge or an engine watchdog alarm?) and that is leaking current into the system, but even then I would hope that the insulated mounts on your radiator would prevent any stray currents from going through the core. If you want to rule this out, disconnect the earth on your battery and then make the measurements. It the voltage difference drops with no battery, you do have a leak and a problem.

[/quote]

The voltage in the water remains after the battery is removed, my mission is to neutralise the current being generated by electrolysis. More flushing and a stronger coolant concentrate maybe.

I will pull out temp sender unit tomorrow to see how it looks.

[date]

Rustyvit:
The fact that the voltage difference remains even with the battery disconnected suggests to me that you don't have any stray currents being induced by installed electrical stuff eg temp gauge, electric fans etc. That is good.

In order for galvanic corrosion to occur, you need a voltage difference and a complete path for the current to flow. You have the voltage difference now. You have half the path for the current (the coolant) and in order to complete the circuit, you need some connection (the body of the car or some electrical components). You cannot reduce the voltage by changing the coolant to stronger concentrations, because there will always be a path for the current to flow whenever you use any fluid which is electrically conductive. The only way you could stop this is to use a non-conductive fluid eg most oils. You have aluminium alloy in the radiator and cast iron in the block. They naturally have a different galvanic potential - you can do nothing about that. You have to eliminate a return path for the induced current ie earth leak, hence they mount the radiator on insulated mounts and use rubber hoses to carry the coolant to and from the engine. If you are getting these voltages, I reckon you have no problems any more. If you had lower voltages, I would be worried because you would have current flowing and that is when corrosion occurs. Check your mate's vehicle(s) - you will probably find similar readings with them as well.

[rustyvit]

Check your mate's vehicle(s) - you will probably find similar readings with them as well.

And there is the problem, I have 2 almost identical vehicles and the other barely registers any voltage from radiator water to earth.

[date]

Sorry - I have run our of ideas. 900 mV seems a lot to me - higher than I feel it should, but I cannot think of anything which would cause readings that high, other than a different metal used in the radiator. Check out this reference to see the voltages... http://www.engineeringtoolbox.com/elect ... d_482.html" onclick="window.open(this.href);return false; and you will find that the difference betwen Aluminium and iron is 1.23 V. Now, depending on the alloying of both the Iron and Aluminium, this will change, but not that much.

Now, you have me worried about my cars.... I have never measured this before, yet I got vastly different readings between cars and of course yours. I reiterate - it you have a higher reading and you don't have any external input (battery disconnected), it means that you have good insulation which should mean less galvanic current.

[rustyvit]

Sorry - I have run our of ideas. .

Hey thanks for the input, I appreciate it.

On the basis that it is in fact a chemical current, I will give it a dose of chemiweld, or the like to see if coating the internals reduces the current, and then a higher quality coolant.

[date]

Rustivit:
There is a lot more to the science than just looking at the Galvanic table. Other features such as the conductive medium (coolant) and the relative sizes of the components affect the indiced voltages, so it is not a simple problem - as you have found out. Getting a coating of an insulating medium (paint) on the inside of the radiator core would certainly help. It may even be possible that the aluminium core starts off raw and then develops its own protective oxide shield (that's how stainless steels work - a thin oxide film which is relatively imperviable to almost anything).

Good luck with your trials - keep us all posted on the outcome.

[love ke70]

I have been through this.

I fitted a sacrificial anode to the radiator.

It is slowing getting eaten despite all my hard work, but that is what its for


do you have a low coolant alarm out of interest?