Electrolytic Effect - rg

The Citroen XM seems to have a reputation for eating radiators and heater matrices due to "the elctrolytic effect". That is, as I understand it, a "battery" effect between two metals eats away at one of them/ both of them. Hence the short life of said parts.

Is this known on any other vehicles, and is there an easy fix?

Electrolytic Effect - wemyss
Don't know the easy fix Rob but I do recall some 40 years or so ago when British cars changed from being positive earth to negative earth.
One advantage stated at the time that there would less corrosion on cars due to less eloctrolytic action, never seemed to make any difference though.
Our main concern at the time was our car radios.
A luxury item at the time with those new transistors and some folks would take them from car to car when they exchanged them.
Some manufacturers made them with a change over switch.
Practical Motorist was full of advice at the time on how to change your car from positive to negative if you chose to.
Going off topic a bit but in plumbing and heating use of sacrificial anodes are made use of in some situations.
And the worst thing that could be done was to fit a galvanised fitting in contact with a brass one.
Electrolytic Effect - Flat in Fifth
Practical Motorist was full of advice at the time on how
to change your car from positive to negative if you chose

Somebody once borrowed the battery off my old H reg Mk 1 Escort.

Afterwards they fitted it back on, and at the time I wondered why the next time I started it the ignition warning light gave a few flashes and then all was normal. Drove like that for a few days without any problem.

Checking the battery acid level noticed that the leads stopped me taking off the caps, to discover they'd wired it up positive earth. Swapped it back, ignition light flashed again and away we went.

Dread to think how much gubbins we'd have wrecked today.
Electrolytic Effect - Edward
Had to have the aircon condensor changed on a 405 a couple of years ago for the same reason. Bloke at the garage said it is common on a lot of makes. Often it is caused by the reaction between the steel P clips used to secure the inlet / outlet pipes and the aluminium of the condensors.

When new, there is a piece of rubber between the two, but over time this perishes and corrosion sets in.
Electrolytic Effect - Phil I
for more info on this subject see


Happy Motoring PhilI
Electrolytic Effect - Shigg
I'm sure an accessory manufacturer years ago used to make some kind of contraption that connected to the battery and to the bodywork to slow the rusting process.

I'm not sure of this but I'm under the impression that in household plumbing you shouldn't use a steel bracket to support a copper tube.

A sacrificial anode was mentioned, is this what is done with ships to stop corrosion?

Any comments?

Electrolytic Effect - Andrew-T
Shigg - don't know about ships, but it is certainly done to protect buried metal pipelines, for example brine mains in Cheshire. Maybe a lot more plastic is used these days, so no problem.
Electrolytic Effect - Shigg
Oh, I see ships were mentioned in the above link.


Electrolytic Effect - M.M

The best you can do is drain and flush the cooling system then re-fill with de-ionised water and quality glycol. Do this every two years without fail and beyond that don't worry about it.

Electrolytic Effect - rg
Cheers, Mr MM, and other chaps.

40K a bit short for a small rad (XM2.5 has 2), I think.

Hey ho. The joys of XM ownership. Should have bought that E-reg Polo...


Electrolytic Effect - lauriew
If it is an all metal radiator(ie not plastic header tanks), then electrolytic action occurs between tubes,solder and tanks. Accelerated by wet/damp debris/roadsalt building up over time.
Best prevention is to keep area clean.

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