Electrolysis in Alloy Radiators

[_ethrty-Andy_ 2122]

unrelated to this but to explain why you shouldn't ground out an alloy radiator.

the biggest part that throws people off is that electricity actually flows from negative to positive not the other way around.

so when a radiator is grounded as alloy its very easy for electricity to flow out of the chassis through the radiator and into the engine.

when it flows like this it takes particles of alloy away eventually eating away at the metal.

this is much much worse when you have the normal ground cable damaged or disconnected.

i have seen an mr2 try to catch fire due to the main ground strap being left off during an engine change and the engine grounded through the throttle cable which got glowing hot very quickly.

wow.

[hybrid 1039]

Has the radiator been opened up and inspected internally to confirm to your theory of the damage? is it possible it may be a different fault?

Don't need to, its leaking (seeping) already out of the multiple brazing points from the core fins to the end tanks. If it was a broken weld it would be in one point only. The way I have it setup its impossible for a twisted frame as well. too much rubber baffling. Once I put the new one in Ill do up a little post with some images and videos of the whole thing.

[crazyarab 6]

Hey Josh!

Sorry to hear man.. As you know I ended up having to fully replace my alloy radiator too!

To get around the issue, I have installed a brass sacrificial rod and I haven't had any issues as of yet since we last spoke.

I haven't had to replace that rod yet either so it's fairly hassle free. Mind you, I'm going to get it checked this week again just in case

[hybrid 1039]

cheers Atta, yeah thinking about doing the same in the expansion tank... mind popping up a photo of the brass sacrificial anode ?

[Nobimmer 694]

How come my one hasn't done that? Am running the same setup -alloy rad with cast block. Only ever had tap water and water wetter in it. Should I do something before it happens to mine?

[hybrid 1039]

Measure the voltage with a multimeter when you have the car up to temperature and see what it reads. If you have the problem you'll be reading over 200-300 millivolts .. if you dont it shouldn't be more than 100-150mv or 0.1 - 0.15v I had 0.5v or 500mv

Physically you might not know you have an issue until its too late and the damage is done. EG it attacks the brazing (welds) first so to speak then onto the other alloys.

[crazyarab 6]

Here is the custom "sacrificial rod" setup I have on my radiator.

What it looked like when I pulled it out... Glad I checked it, it's BUGGERED! That's nearly 2 years of corrosion...

It was so bad, when I came to sand off the corrosion the whole rod snapped! Much better that than my bloody expensive radiator

Popped into A1 Radiators, the guys who set this up for me and got a replacement. Interestingly enough, they were stoked to see the old sacrificial rod and wanted to keep it to show future customers... They are now using this technique frequently so it's nice to see that my project contributed to something "new" in the industry.

Edited November 6, 2013 by crazyarab

[polley 916]

Im getting about 220 - 280mv, radiator is not grounded, using BMW coolant. Time to start pulling fuses and see if it changes?

[hybrid 1039]

let us know how you get on ... just bought a house so wont be looking at this till the holiday period (fun times moving) but will post results.

[hybrid 1039]

Installed the new radiator this weekend ...

Before: 0.45volts hot with tap water and standard quality coolant

After: New radiator, demineralised water and BMW coolant on 2:1 mix actually increased the voltage hot to nearly 1volt!. Measured from the coolant and the radiator. When I looked inside the old radiator I had noticed that the inside was anodised black .. and therefor not conducting as well and the brand new radiator.. This explained the voltage increase.

I wanted to data log it but the current was playing havoc with other sensors so just rigged up a multimeter to the radiator instead and drove around and took readings.

Solution: First I tested what happened if I used a small wires and grounded it to the chassis .. boom, down came the voltage to 0.002v perfect .. So now have run an earth strap onto the radiator to eliminate the voltage build up in the radiator.

This has been a very enlightening experience and while loosing a chunk of cash down the toilet I have learnt a lot.

Just got off the phone with the old man who's an industrial electrical engineer and done some pretty far out stuff in his time confirmed everything I found and even said that he found it strange that I had isolated the radiator in the first place!

[polley 916]

So now we are saying we should ground the radiator, when at the start of the thread we were supposed to be doing the opposite?

[hybrid 1039]

Yup .. I followed advise I was given at the time of install (Not you Atta ) Like trying to find anything solid on the interwebs .. its mostly full of s**t and full of people who think they know what they're talking about ... But when it comes down to it they're confused and got it off the next confused person. However to be fair these days there is less confused information around. EG the Denso whitepaper I posted earlier.

Reading 3pedals post made me stop and break it down to basics to actually work out what was going on. That and creating a solid test which I could conduct easily over and over to do before and after comparisons. That and talking to someone who is actually an expert (my father) and not an automotive person.

Basically, there are two fixes needed for this. Chemically and electrically. Chemically by reducing the risk of creating a battery by using demineralised water and in my case switching to known good BMW coolant mix and electrically removing the ability for it to be a battery by grounding the radiator to the chassis which is acting as the anode (+) .. the engine as the cathode (-)
standing voltage = gone.

In my case remember Ironblock s50 and alloy radiator ... this is a pretty extreme case. Most hotrodders will run a brass radiator not alloy to get around the issue.

[Ahmedsinc 414]

Thanks for doing all the hard work Josh. Will be getting on to earthing mine this weekend. Any particular gauge cable recommended?

[polley 916]

I would of thought iron block / alloy head with alloy radiator was quite common to be honest. Just look at standard BMW setups. E30, E36 etc.

Iron blocks, alloy heads, alloy radiators albeit plastic end tanks but the alloy cores are not grounded and they are mounted via the plastic end tanks with plastic clips.

[hybrid 1039]

OEM radiators are manufactured a lot differently that a full alloy custom radiator. Probably why the press fit plastic end tanks to get around the issue the problem is the lead braising in the core fins.. it gets eaten by the electrolysis and leaks. Apples with apples and all that.
I have a strong feeling this is why there is so much crap on the net. People get confused easily by drawing conclusions. People like me looking for real answers get lead astray.

[hybrid 1039]

Thanks for doing all the hard work Josh. Will be getting on to earthing mine this weekend. Any particular gauge cable recommended?

Not sure, I used a spare press fit 8 gauge earth wire. However I would recommend testing it yourself first to see if you even have any issues.

Bring your coolant up to temperature (around 80 degrees) and open the radiator cap carefully. It shouldn't be pressurized yet .. take a multimeter and put the positive into the coolant and negative onto some where on the radiator. Measure your voltage from there.

[polley 916]

Is lead still used these days? I cant imagine the process used for welding the fins / channels / tanks ends been much different other than having a plastic or alloy end tank.

[hybrid 1039]

How did you get on with testing yours Troy ?

[polley 916]

Havent touched it, weather has been far better for motorbiking around than burning around in a car with no A/C.

[polley 916]

Thinking about it over lunch, I think you've made the problem worse by grounding it. It would seem the problem has gone because you've effectively shorted it out. I would expect your radiator to fall apart even quicker like this...

Can you measure the current flowing through the earth strap?

If you think of it as a battery with cells, and electrolyte, you will measure a voltage between cells.but there is no current flowing because there I'd no load attached. Ie, you can measure a voltage potential in your radiator but without it grounded there I'd no where for the current to for. Soon a you ground it (put a load on it) current will flow and voltage will drop (making you think you fixed the problem)

[hybrid 1039]

It cant hold a charge because there is no cathode or anode by shorting it. The charge is what initiates the electrolysis reaction converting iron into iron oxide. No charge = no chemical reaction possible. eg no where for electrons to flow, or simply putting it there isn't an environment anymore for it to build up a charge.

Measured the coolant, measured at the radiator and ground points and measured at the block and ground points.

I think you are confusing voltage and current. Load will dip voltage and drain current. What is happening is if it does build up voltage it is expelled very quickly with the earth strap connected because of the above.

Ideally you want to ground it to the battery as the chassis does hold an amount of resistance between the ground point from the radiator and battery ground point in my case the boot as e30 325's do. The only potential difference is between these two ground points. It is very minimal and within the design parameters of a standard vehicle 12 volt system.

[polley 916]

I think also you are confusing voltage and current. Load will dip voltage and drain current. What is happening is if it does build up voltage it is expelled very quickly with the earth strap connected because of the above.

Im not confusing current and voltage, my post might not make complete sense as I wrote it on my phone. If I was confused then I better resign from my day job first thing monday.

Goodluck with your radiator replacement goals of 2014.

Edited December 1, 2013 by polley