Failure of Alluminium Radiators due to electrolysis

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Failure of Alluminium Radiators due to electrolysis

Postby 85_Z31 » Mon Mar 30, 2015 4:39 pm

Hi All, below is a couple of Articles from Denso About how diagnose and prevent damage to your Cooling system and aluminum radiator.

See the bold points for what i feel is the most important from all of those words.


Looking After Your Radiator
It is imperative that the correct coolant is used and that it is well maintained to ensure long life from your radiator. Coolants must not be mixed and must be replaced when stipulated by the manufacturer - it may look the same after this date, but may no longer be doing its job.
Aluminium is normally seen as corrosion resistant because an oxide layer forms on the exposed surfaces that acts as a barrier to further corrosion. However, in conditions where this barrier is broken, corrosion can be very rapid as aluminium is actually a very reactive metal. This is why care of the coolant becomes even more important when using an Aluminium radiator.
Copper/brass cores are quite tolerant to water quality and although there are some chemicals that can cause problems, and corrosion inhibitors must be used, normal tap water is reasonably well tolerated. The same does not apply to aluminium cores.
A few important points to note regarding coolants:
1. Use the correct coolant specified for the vehicle. Coolants are selected to suit the vehicle. The requirements for aluminium and copper brass radiators are different and a common coolant may not suit. The radiator is not the only part of the coolant system and some coolants may have been selected to protect other parts of the cooling system.
2. Use the correct concentration of coolant. Coolants for aluminium radiators are mainly composed of ethylene glycol but also contain chemicals to protect the cooling system. High-ethylene glycol content will actually reduce the heat rejection performance of the cooling system*. This results in the engine running hotter than normal when the thermostat is fully open.
3. Always use good quality water to blend with the coolant. Distilled water, demineralised water or rain water are the preferred options. Many town water supplies contain high concentrations of chemicals, such as salts, that are very damaging to an aluminium radiator.
4. Do not mix coolants. Many coolants use different chemical systems and combining them may neutralise the effect of the chemical protection.
5. Replace the coolant at the specified intervals. During service the ethylene glycol eventually deteriorates and becomes acidic. This acid will attack the internal oxide coating on the aluminium and lead to corrosion.
6. Flush the coolant system with clean water after the coolant is drained. It is important to remove any scale or deposits from the system and remove old coolant and chemicals that may adversely affect the new coolant. The heater core is part of the cooling system and must also be flushed of coolant.
7. Check that the system is properly filled and that any air is removed. Air in the coolant will increase the rate of corrosion and air pockets can lead to uneven cooling of the engine. Some vehicles have trapped air pockets and it may be necessary to bleed air from vent positions to allow the air to escape. The vehicle should be run for a while before the cap is replaced to allow the air to escape.
8. If the coolant is topped up it should be with a properly mixed coolant solution so that the concentration of the system is not changed. Ensure that the coolant type is the same as is already used in the vehicle to ensure it is compatible.
*Low-ethylene glycol content will not carry the required concentration of additives and can also result in an incorrect Ph level. This leads to damage of the radiator due to corrosion. NOTE: Ethylene glycol is toxic. Please follow specific manufacturer instructions for handling and disposal. It is also important to clean up spills.
Radiator Service
DENSO advise the use of authorised radiator repairers or your vehicle dealer. Generally, cooling systems should be serviced yearly.
Your radiator specialist will flush and replace your coolant, clean off road debris and check for possible problems such as corrosion, blockages, leaks, hose wear and tear, etc. Preventative maintenance assists in preventing breakdown due to over-heating.
Genuine parts are recommended for optimal efficiency as these parts are designed specifically for the vehicle model. A change of components may affect performance of the cooling system. DENSO copper/brass NWR and NSR radiators may be replaced with equivalent DENSO Aluminium NSR radiators in some instances. In these cases the direct equivalents have been designed to suit the application.
Radiator Care
Ensure radiator coolant level is correct. In newer cars this is as easy as looking through the plastic reservoir wall to check fill lines are covered. Coolant can be added via the reservoir (when cold) if required (refer to section on coolants).
For vehicles without a reservoir, remove the radiator cap and check coolant level while the engine is cold. Also check if coolant looks rusty, or has things floating in it - if it does, the system needs flushing and new coolant. If it has a sludgy oily surface get your mechanic to check for the reason.
While checking the radiator, ensure that the hoses are not leaking, cracked, bulging or squishy. If they are, they will need to be replaced.
What to do if your car overheats
If your radiator overheats, pull over and raise bonnet to assist cooling. Do not remove radiator cap or add cold liquid. Allow time for the radiator to cool down, liquid should only be added to the radiator when it is cool. Apart from the danger of being burnt by the radiator, removing the cap when hot will cause hot liquid and steam to surge upwards as the pressure in the system is released. Adding cold liquid to a hot radiator can also crack the engine block. If you must add liquid while it is still a little warm have the engine running to mix the cooler liquid as it is added and add slowly.
Causes of Premature Radiator Failures
• Corrosion - Internal & External
• Erosion - Internal & External
• Stray Current - Electrolysis
• Mechanical Damage
Chemical corrosion is often due to incorrect coolant use. Corrosive atmospheres, road grime and stray current in the cooling system are also potential problems. Qualified Auto Electricians and Radiator Repair Specialists use a voltmeter and a specific procedure to test for stray current.
Mechanical failure includes tanks splitting and separation of fin to tube bonding. It is often caused by excess pressure in the system, possibly from a blown head gasket or even a radiator cap. A faulty swollen radiator cap or incorrect one can prevent pressure release with severe consequences. Alternatively, poor radiator cap sealing can lead to the loss of coolant, loss of system ability to draw coolant back from the overflow reservoir and to boiling of the coolant under severe operating conditions.

Radiator failure information from Denso & NRMA.

Premature radiator failure-/causes.
Corrosion ¬- Internal and External.
Erosion - Internal and External.
Stray Current - Electrolysis Internal- External.
Mechanical Damage - External.

Stray currents cause premature corrosion failures in radiators, water pumps and thermostat housings as well as premature ageing in coolant hoses. When we say premature, we mean in as little as three months.
NRMA Insurance did a front end repair on a VW Golf in which the radiator was replaced, three months after the owner took delivery it was found that the new radiator was so badly corroded it was irreparable. The radiator core was dismantled and showed evidence of extensive electrolysis and mixed coolants.
Do’s and Don’ts:

Never mix different brands of coolants or inhibitors. Mixture of incompatible coolants can induce radiator fouling and can reduce the corrosion protection of the coolant. Always flush out the cold coolant.

•Never use coolants that foam as this will lead to increased cavitation erosion of the water pump. Shake the bottle of coolant then let it stand for 5 seconds, if the foam has broken and the fluid has returned to normal then it probably won’t foam in the cooling system. If the foam has not broken after 5 seconds then it might pay to find another product.

•Never under treat a cooling system as the incorrect ratio of coolant can actually increase the corrosion rate to above that of plain water.

•Only use the best quality water. De-mineralised is the best, never use bore or spring water.

•Always check for stray electrical current in the cooling system.

•If the vehicle is within the new vehicle warranty period, always use the manufacturer’s recommended coolant as to do otherwise could void the warranty should the cooling system fail.

•Always use the service stickers supplied by the coolant manufacturer to avoid any confusion as to which type of coolant is in the system when a top up is required.

•Always dispose of used coolants correctly. All used coolants will contain heavy metals irrespective of their claims of being environmentally friendly.

“Whilst not wanting to pick on any one area of the automotive industry, our own experience tells us that many vehicles we have examined for electrolysis and chemical corrosion damage are those that have had recent paint and panel repairs. If you suspect that a radiator has failed from electrolysis and you can’t find any apparent reason for it, look for signs of recent repairs (keep in mind that the problems can exist right from the time the vehicle was manufactured)

If you spot repairs, be wary of earth wires that:

1. Are not connected.

2. Are loose, corroded or insecure.

3. Earth wire mounting points have recently been painted, thus paint may be down the threaded holes causing poor earth contact.

4. Whist you are monitoring the presence of stray voltage in the cooling system, have a fellow worker operate the brake lights, parking, head and high beam lights and check for any increase in voltage readings in your multimeter

5. Also, turn on as many accessories as you can to load the vehicle’s electrical system whilst monitoring stray current.

6. Check battery cables and mid cable securing points for corrosion and tightness.

Testing for Stray Current:

Using your multimeter, connect one lead to negative side of battery and then with a test probe immersed in the coolant, make sure it doesn’t touch the core and for a proper reading the probe must stay in the same place in the neck at all times. If a current measuring above 50mv is present you then have to start looking for the source.
At this point, we have to say that if you have found a problem relative to the stray current, CHANGE THE COOLANT. Unfortunately we have found with some brands of coolant that their chemical composition does not allow them to dissipate the charged oxygen hat has resulted from stray current, so if you are unaware of the coolant in the system, flush it and replace it.
Common Sources of Stray Current.

•Ford Laser: Multi earth plugs located at the front of both chassis rails, Check the thermo fan earth circuit.

•Ford Falcon: Main battery earth cable fitting at the engine block. Wiring harness fitting at the right front inner guard.

•Holden Commodore: Main battery earth cable fitting at the engine block. Rear stop light wiring harness earths. Earthing point located behind right front headlight.

•Nissan Pulsar: Brown coloured earth cables attached to right side rear cylinder head bolt. ECU earth. Earth circuit for thermo fan.

•Early Hyundai’s: Multi earth wire point located at left front inner guard, cut this off and replace with eyelet connectors.

•Sigma/Magna: Main battery earth cable (both ends)

•Nissan Skyline/Pintara: Air conditioning fan earth circuit, change from condenser mounting to adjoining radiator support panel threaded hole.

Unfortunately, in recent times we are coming across more and more cooling systems and engine failures associated with chemical corrosion. It is a problem common with poor quality inhibitors, low dosages of inhibitor, but we see many where different brands of inhibitors have been mixed and the results are catastrophic.

The mixing of different brands can degenerate into the formation of a chemical cocktail, which can strip metal away with amazing speed.
The internals will show a dark Grey or black discolouration. You can also try removing the radiator cap and feeling the top of the core tubes, they will feel flexible, even soft to touch.
Where this indication is present you may also find items such as thermostat housings and water pumps showing signs of cavitation.

Where chemical corrosion has occurred, quite often the cooling systems components such as the thermostat housing, water pump, heater and coolant pipes will be badly discoloured.
Chemical corrosion can also lead to the formation of small hard deposits of metals and rust within the radiator or engine block causing hard to find overheating problems. These deposits can be very hard to shift if they have been building up over a period of time and as such, become firmly lodged in coolant tubes and within water passages, etc. Keep in mind that 1.6mm of corrosion build up on aluminium causes as much heat retardation as 10.4mm of cast iron.

Mixing of coolants and even poor quality coolants can cause foaming and it’s the introduction of oxygen that leads to the formation of air bubbles that create their own version of cavitation erosion.
The bubbles or vapours, which result from the chemical activity, continually explode against the engine’s hot spots and if not caught early can completely destroy an engine. The exploding bubbles of air cause a hammering effect on the metal gradually eroding away that area and eventually forming a small pin hole. Often a large piece of metal will simply disappear from within the engine. Cavitation can be particularly harsh on cylinder liners and their seals and at different points of the cylinder head and gasket.

Stop Press
Don’t assume that fitting an earth wire directly to the radiator core is a fix all, We did a test on an aluminium core and the wire actually increased the current.

Stray Current explanation & testing procedure:

In simple terms stray current is a chemical/electrical process which causes an electrical current to pass through a vehicles cooling system fluid. It can cause rapid damage to radiators and will indirectly cause problems with other engine components such as water pumps, thermostat housings, etc.
This is brought about when one or more items such as a cooling fan or headlamp develops a problem in its electrical circuitry. This causes an electrical current to seek out an earth path via the radiator core through the engine coolant.

•Remove the radiator cap and run the engine to operating temperature. Do not rev the engine as this may cause the coolant to aerate. Note: Removing the cap will reduce the boiling point of the coolant. This may result in electric cooling fans not operating on some vehicles,

•Switch ON all electrical items including Items such as a mobile phone, rear demister, driving lights, etc.

•Switch an analogue multi-meter to a scale of 5 volts DC or less. Ideally the meter should be capable of reading millivolts. Do not use a digital multi-meter, as its internal operating characteristics are not suitable for this test.

•Place the negative lead of the multi-meter on the battery negative post.

•Dip the positive lead into the coolant without touching the filler neck or the core of the radiator

•A reading of more than .05 volts indicates the presence of a potentially damaging stray current passing through the coolant. Ideally the voltage should be 0 volts, however it is highly possible that some voltage level will be detected

•If no voltage or a very low voltage is detected, carry out the same test as in point 4, but with the ignition OFF.

•If voltage is detected, isolate the circuit by turning all electrical items OFF and switching each circuit ON individually.


Refilling a cooling system with coolant will itself generate a current that lasts approximately twelve hours.
This can be avoided by refilling a repaired vehicle, for example, with clean water and then proceeding to test for stray current.

Cooling System Flushing Procedure:

Because coolant/inhibitors from different manufactures have different chemical compounds, which may adversely react if mixed, it is important that you DO NOT create a chemical cocktail within your cooling system by mixing different brands of coolant/inhibitor. Even though the coolant has been drained from the system, the inhibitors remain affixed to the cooling system components and must be chemically removed, using a quality alkaline flush.


1. Ensure the cooling system is sound and free from leaks and check all components for wear and condition. If need, replace worn components.

2. Choose a quality alkaline cooling system flush (500mL. Per 12 Litres). Observe the instructions on the container.

3. Replace the radiator cap and run the engine at operating temperature for 15 minutes in 4 cylinder vehicles and 30 minutes in 6 or 8 cylinder vehicles. (Ensure the vehicle heater is turned on).

4. Drain and rinse the cooling system including the overflow bottle and heater core. At this point a power flushing machine may be used if this equipment is available.

4a). Rinse the system with clean water until you are convinced that the only fluid remaining in the system is clean water- RINSE- RINSE- RINSE (this may need to be refilled and drained a number of times).

5. Refill the cooling system using clean water (demineralised or distilled water), to perform a stray current check.

6. Do not add coolant at this time until a complete stray current check has been performed (refer to stray current procedure). The presence of stray current will deteriorate the cooling fluid quality immediately.
Always ensure you select a coolant/inhibitor that meets the vehicle manufacturers recommendation or one that meets AS 2108-97 Type A or Type B whichever is recommended as being in support of the vehicles manufacturers recommended coolant performance standard.

7. Ensure the correct rates of coolant/inhibitor is used, as overdosing or under-dosing will have a direct affect on the performance of the cooling system and the life of the components including the radiator.

8. Only after the vehicle has been cleared of the possibility of stray current (electrolysis). Rebuild the cooling fluids by first adding the selected product then topping up with clean water (demineralised or distilled water). NOTE: NEVER MIX TWO BRANDS OF COOLANT!

9. Mix a portion of the coolant for the owner to use for topping up coolant level.

Dispose of Waste Fluid Correctly.
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Re: Failure of Alluminium Radiators due to electrolysis

Postby Datto_610 » Mon Mar 30, 2015 9:35 pm

Good work James! Although I didn't read the whole thing I will test to see if my ali rad is isolated or not!
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Re: Failure of Alluminium Radiators due to electrolysis

Postby 85_Z31 » Mon Mar 30, 2015 10:08 pm

Yeah, in one sentace the Go of it seems to be.

Isolate the radiator, flush everything perfectly, use good quality coolant mixed correctly. and check the voltage across the coolant to the negative battery terminal for a voltage and earth out the block and heads quite well.

I didn't really do much it was just a copy paste. Theory seems to be that if the radiator is earthed it can create another path for stray currents to attack the aluminum.

Its also worth pointing out that this is the same chemical process as Anodizing or plating its just that the whole radiator becomes the anode.
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