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Stray current corrosion

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rustyvit

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Post Mon Jan 05, 2015 6:35 pm

Stray current corrosion

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
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CRUZAAMAD

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Post Tue Jan 06, 2015 8:07 pm

Re: Stray current corrosion

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
AUSTRALIA
WORTH LOOKING AT WORTH LOOKING AFTER
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date

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Post Tue Jan 06, 2015 9:04 pm

Re: Stray current corrosion

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.
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rustyvit

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Post Wed Jan 07, 2015 4:13 pm

Re: Stray current corrosion

date wrote: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. :crazyeyes:
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DamTriton

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Post Wed Jan 07, 2015 4:23 pm

Re: Stray current corrosion

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


two dissimilar metals (iron, aluminium) and an ionic solution connecting them, with your meter across both metals = a battery.
George Carlin, an American Comedian said; "Think of how stupid the average person is, and realise that half of them are stupider than that".
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rustyvit

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Post Wed Jan 07, 2015 7:43 pm

Re: Stray current corrosion

DamTriton wrote:
rustyvit wrote:
With battery disconnected, engine block to radiator coolant is still 0.47 which is confusing me. :crazyeyes:


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 :crazyeyes:
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Post Wed Jan 07, 2015 8:54 pm

Re: Stray current corrosion

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.
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rustyvit

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Post Thu Jan 08, 2015 3:37 pm

Re: Stray current corrosion

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)
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Post Thu Jan 08, 2015 6:54 pm

Re: Stray current corrosion

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.
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rustyvit

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Post Thu Jan 08, 2015 7:28 pm

Re: Stray current corrosion

[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.
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Post Fri Jan 09, 2015 7:24 am

Re: Stray current corrosion

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.
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rustyvit

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Post Fri Jan 09, 2015 2:27 pm

Re: Stray current corrosion

date wrote:
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. :bad-words:
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Post Fri Jan 09, 2015 4:03 pm

Re: Stray current corrosion

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 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.
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rustyvit

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Post Fri Jan 09, 2015 7:51 pm

Re: Stray current corrosion

date wrote: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.
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Post Sat Jan 10, 2015 8:06 am

Re: Stray current corrosion

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.
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Post Wed Oct 07, 2015 9:10 pm

Re: Stray current corrosion

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?
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rustyvit

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Post Sat Dec 03, 2016 11:39 pm

Re: Stray current corrosion

I will post an update on this issue, should have done it earlier.

I talked to a heap of industry people about the issue and while every one has heard of chemical electrolysis, very few have had any experience with it first hand and fewer had a definitive resolution. It appears to be a real grey science sort of problem.

I hit a wall with ideas to rectify the high current, ran coolant, rain water, distilled water, demineralised water, tap water, different coolants, multiple cooling system cleaner and flushes.......and nothing changed the current flow. I looked at a couple of products that claimed to reduce, fix chemical electrolisis but were very vague about application and sounded like bullshit to me. Bar's leak, as well as being a sealer claims to be an engine conditioner, so I put the radiator that had the electrolisis hole back in and gave it the Bar's leak treatment and ran around for a few weeks to see if it had any affect on the current. Bars leak plugged the hole in the radiator, but there was no reduction in current, at least I felt better knowing that it was eating the old radiator and not the new one.

Most of the running was around town and under 70KPH, first time the vehicle ran at 110 KPH it immediately began to overheat, I suspect the Bar's leak had plugged up radiator tubes as well as plug the hole, no problems at lower speeds.

Pissed of and totally out of ideas, I cleaned and flushed the system, put the new radiator back in and filled it up with the high concentrate Natrad organic coolant, and pretty well said fuck it I'm over it , would be cheaper to buy radiators in bulk that invest the time that I already had.

Well almost 2 years and 20 000 km later all is well, current began reducing after a couple of months and to be honest time got away from me and here we are at almost 2 years. Before posting, I should have checked the current range but my young bloke has the vehicle.

So it appears, like others before me, I have no definitive answer to this issue.
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date

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Post Mon Dec 05, 2016 1:42 pm

Re: Stray current corrosion

Not sure where this all ended, but one thing I would do would be to ensure that you have an adequate earth connection from your engine/transmission to the body. You need this for the starter motor to operate anyway. If you have a good connection, the voltage difference between the coolant and the radiator should be considerably reduced. Is the radiator mounted on insulated washers? If it is, are they in good condition? Many radiators are mounted these days in rubber mounts which act as a vibration damper as well as an electrical isolation. Have you talked to a radiator specialist? They may be able to help you with some useful experience.
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rustyvit

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Post Mon Dec 05, 2016 9:36 pm

Re: Stray current corrosion

date wrote:Not sure where this all ended, but one thing I would do would be to ensure that you have an adequate earth connection from your engine/transmission to the body. You need this for the starter motor to operate anyway. If you have a good connection, the voltage difference between the coolant and the radiator should be considerably reduced. Is the radiator mounted on insulated washers? If it is, are they in good condition? Many radiators are mounted these days in rubber mounts which act as a vibration damper as well as an electrical isolation. Have you talked to a radiator specialist? They may be able to help you with some useful experience.


The radiator was rubber mounted, all earths intact and good connection. Remember this was current in the coolant and that current remained after the battery was removed and earths disconnected.

The radiator specialist didn't really have anything useful to ad, but had heard of it and had very limited experiences

Anyway, its all good now, the only conclusion I could come to was that the final coolant conditioned or at least neutralised internal conditions of the cooling system eventually.
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Post Sat Dec 10, 2016 8:22 am

Re: Stray current corrosion

Galvanic corrosion occurs because you have a voltage difference between two metals, and an electrolyte to carry the current. Once the curent flows, it takes some of the metal from one to the other - corrosion. You don't need your 12V battery for this to happen - it is a natural phenomenom and happens all the time.

The voltage difference you have noted comes from the fact that you have a cast iron block, and aluminium head and maybe now a copper radiator. This is like a battery in itself. The coolant is the electrolyte in the equation. The way I see it is that if you are getting radiator damage, you must have a connection to earth at the radiator. It if is fully insulated, the voltage could be enormous but no damage would occur to the radiator. As soon as it is earthed, you get current flow through the radiator and then corrosion. This is why they mount the radiator on rubber mounts, yet I have seen the radiator screwed with bolts on the side flanges directly to the body. OK - the bodywork was painted at the connection points, but you could still get electrical connection. If you still have problems, I would look at the side mounting of the radiator and see if you can insulate it there.

Incidentally, this is one of the reasons I didn't buy a low coolant level alarm - because it gives another potential path for galvanic current to flow.

Another possible way out of this is to look at the coolant. Maybe you could chase up a coolant which is electrically non-conductive (if such a thing exists)? In the old days they used soluble oil, but that was when they had cast iron blocks and heads, with copper radiators. It is very confusing....
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rustyvit

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Post Fri Dec 16, 2016 5:19 pm

Re: Stray current corrosion

date wrote:
Another possible way out of this is to look at the coolant. Maybe you could chase up a coolant which is electrically non-conductive (if such a thing exists)? In the old days they used soluble oil, but that was when they had cast iron blocks and heads, with copper radiators. It is very confusing....



I haven't had anything to do with waterless coolant products, and whether they would help problems like this. Have you ever used any of them?

My radiator was plastic tank ally core, rubber mounted and no earth.

Hopefully this problem doesn't raise its ugly head again. :shock:
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Post Sun Dec 18, 2016 9:34 am

Re: Stray current corrosion

I would check the mounting bolts on your radiator. Do they have insulating washers? Should they have them? I don't know. If they don't, I would check another cehicle similar to yours and see what the voltages etc are.

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