Water water everywhere.................

[moggiethouable]

And I wondered why that jubilee clip couldn't cure the leak.
Clearly aluminium and anti-freeze don't get on well.

[svenedin]

Firstly it needs to be the right type of antifreeze and secondly the coolant needs periodic draining, flushing and replacing. The antifreeze effect is not affected by time but the corrosion inhibition effect is used up over time. I have also found that the coolant stays pristine much longer by using distilled or deionised water such as is used to top up batteries or in steam irons. The water collected from a condensing tumble dryer is also suitable.

Many owners are fastidious about oil changes but seem to forget changes of coolant and brake fluid.

Stephen

[svenedin]

This an a AI summary of the processes that corrode aluminium in a car's cooling system. It's actually a much better and more comprehensive summary than I could write!

Stephen


Aluminium is a highly reactive metal, and its use in car cooling systems makes it susceptible to various types of corrosion, primarily pitting, galvanic corrosion, and electrolysis. These issues are managed by using specific, high-quality coolants with inhibitors and proper system maintenance.
Types of Aluminium Corrosion in Cooling Systems
Pitting Corrosion: This is the most common type, usually triggered by chloride ions in the water (like tap water). It penetrates the naturally occurring protective oxide layer on the aluminium surface, creating pinholes and leaks over time.
Galvanic Corrosion: This occurs when two electrochemically dissimilar metals (e.g., iron engine block and aluminium radiator) are in electrical contact within an electrolyte (the coolant). The more reactive aluminium acts as an anode and corrodes faster than the more noble iron (cathode).
Electrolysis (Stray Current Corrosion): This happens when stray electrical currents flow through the conductive coolant due to poor grounding or faulty electrical components. This accelerates metal degradation, especially for softer aluminium components like heater cores and radiators.
Acidic/Alkaline Attack and High Temperatures: The protective oxide film on aluminium is stable within a specific pH range (around 4.0 to 8.5). If the coolant becomes too acidic or too alkaline (due to age, contamination, or oxidation of ethylene glycol at high temperatures), it rapidly attacks and dissolves this layer, leading to corrosion.
Managing Reactivity and Preventing Corrosion
To prevent premature failure of aluminium components, specific maintenance and fluid choices are critical:
Use Proper Coolant: Modern coolants, especially Organic Acid Technology (OAT) or Silicated OAT (Si-OAT) formulas, are designed with specific corrosion inhibitors to protect aluminium and magnesium alloys. They form a protective layer on the metal surfaces.
Avoid Mixing Coolants: Mixing different types or brands of coolants can cause the inhibitors to become imbalanced or form precipitates (gel formation) that clog small passages and accelerate corrosion.
Use Distilled Water: Always dilute coolant concentrate with distilled or purified water, never tap water, which contains minerals and chlorides that promote corrosion and electrical conductivity.
Regular Flushing and Replacement: Coolant inhibitors wear out over time, typically every two to five years depending on the formula. Regular flushing and refilling with fresh, appropriate coolant are essential maintenance.
Check for Stray Voltage: Periodically test the coolant for electrical currents using a voltmeter. A reading over 0.3 volts indicates a potential electrolysis issue that requires tracing and fixing the electrical fault (e.g., bad grounds).
Isolate Metals (where possible): Many modern vehicles use rubber mounts or plastic end tanks to help insulate the aluminium radiator from the iron engine block, mitigating galvanic corrosion. Sacrificial anodes (zinc or magnesium rods) can also be added to the system to protect the aluminium.

[moggiethouable]

Thanks for the info, it is also interesting that I replaced the offending item around 4 years ago, replacing what looked like the original from 1965.
So one lasted 50 years or so and the modern pattern equivalent 4 years.
Anyways up, its an easy fix and I have replaced the jubilee clip with a broad banded "Superclamp" unit.
Heater valve next, that also was new a few short years ago, but I understand they have history.

[svenedin]

Thanks for the info, it is also interesting that I replaced the offending item around 4 years ago, replacing what looked like the original from 1965.
So one lasted 50 years or so and the modern pattern equivalent 4 years.
Anyways up, its an easy fix and I have replaced the jubilee clip with a broad banded "Superclamp" unit.
Heater valve next, that also was new a few short years ago, but I understand they have history.

It's very likely that the alloy is different in the original housing and the modern copy.

I did see your post about the heater valve. ESM sell a cable-operated valve that seems well made. I have had trouble with a heater valve that gave up in an enormous leak of scalding hot coolant at a set of traffic lights. That was one of a notorious poorly made batch some years ago. The new valves from ESM seem better but I have had trouble with one of those as well. In that case it would not stay shut but it did not leak externally.

Stephen

[ndevans]

Surely not aluminium if it has reacted that badly? Some sort of low grade whitemetal perhaps?

[Bill_qaz]

Surely not aluminium if it has reacted that badly? Some sort of low grade whitemetal perhaps?

Its known as chinesium alloy
I believe the warranty is 5min or 5 miles, whichever comes 1st

[geoberni]

Surely not aluminium if it has reacted that badly? Some sort of low grade whitemetal perhaps?

Even the highest grade can do that if unprotected; for all the reasons listed in the AI summary that Stephen shared.

One of the biggest issues in classic/historic aircraft preservation is aluminium 'corrosion' for aircraft left outside, which is typically the larger ones of which there are already fewer examples retained.
What tends to happen is they get to a point where the corrosion is so severe on critical structure e.g. Main Wing Spar, that they cannot be saved. They literally get broken up before the wings fall off.

Sometimes it's galvanic action from dissimilar metals, such as the fastener (i.e. rivet), the skin panel and the structure it's secured to. Other times it's just water (and salts) getting under the surface finish...

corroded skin.JPG (58.01 KiB) Viewed 3044 times

But corrosion is a problem that affects aircraft practically from the moment they are built; it's a constant programme of inspection and preventative maintenance that keeps them flying.

[myoldjalopy]

"....corrosion is a problem that affects aircraft practically from the moment they are built; it's a constant programme of inspection and preventative maintenance that keeps them flying."
One could say the same about our cars!

[geoberni]

"....corrosion is a problem that affects aircraft practically from the moment they are built; it's a constant programme of inspection and preventative maintenance that keeps them flying."
One could say the same about our cars!