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I have noticed that inside the filler holes on my ally (ASI) radiator there is some black crusty stuff...Is this the start of a corrosion problem?

Do I need to figure out some sort of sacrificial anode? What have others done?

An anode will not work, at best you might protect half of the tank and none of the core.

Aluminum actually oxidises very quickly, but the oxide sticks and prevents further oxidation. Aluminium oxide is quite dark but will generally be smooth rather then crusty.

Post a photo if you want, but basically the anti corrosive in your radiator fluid should stop any corrosion.

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Seconding the normal antifreeze/anti corrosion stuff, that is all you need.

Green is good

Years ago there was a big thread about radiators and anodes. Quite a bit of scientific discussion. Of course I can't find it...

I can tell you it is not effective.

To get technical, you get basicly 4 times the diameter of your vessel where the anode is effective. This means if you put the anode next to a cooling bar pipe 1mm in diameter then you get roughly 4mm down that pipe and your anode stops having an effect.

Better then electric rust proof though! That is a huge con!

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sailaholic wrote:Better then electric rust proof though! That is a huge con!

Does that even work in theory?

Every car I've seen with an "electric rust stopper" or whatever, installed has had massive bits of rust forming around where the device it attached.

Depends on the system as to how close they get to almost working under the right conditions.

The best are fundamentally flawed unless you park your car in water (immersed). And have huge battery capacity. Some don't even attempt to follow the theory.

Electronic rust prevention is based on the concept of cathodic protection which does work. But the thing your protecting and your anode have to be in a common electrolyte. Hence why anodes work on boats and not cars bodies.


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Thank you chaps. I did not manage to get a picture yet...it is at the bottom of the filler neck on the radiator that there is some black stuff that is crusty and breaks off. I can not see anything in the core of the radiator.

I had a brief read on something earlier that mentioned that it can actually be bad to have an anode in a car system as it reduces how well the anti-corrosion stuff in coolant works.