[Vwdiesel] More on radiator as a battery (weekend science thread)

[Mark Shepherd]

Gary says...
I think we need to step back and find out why electrolysis
is happening.

Electrolysis is Galvanic corrosion... when two dissimilar
metals are in
a contact in conductive solution.

Grounding the radiator will only compound the problem.

....Explain this; as if the battery-ve and chassis is at
zero then grounding the rad would make this zero andas the
coolant is conductive it would be like a conductor attached
to amongst other things the engine block As it stands the
rad is the only thing that is not grounded???
 Action of dissimilar metals is the Thermocouple principle
so there needs to be a 'hot' junction and a cooler junction?
And there needs to be a circuit...
Step 1: We need to electrically isolate the radiator. There
is a reason
they came from the factory with rubber mounts.
...I thought it was a vibration thing...

Step 2: Use fresh uncontaminated coolant mixed with
de-ionized or
distilled water. Distilled water will not conduct
electricity.

...As soon as you add the glycol it becomes conductive???...

Step 3: While the use of a sacrificial metal will redirect
the corrosion
to that metal, it will release metallic corrosion products
into the
coolant which in turn will be deposited throughout the
system as sludge
and scale.

...But this is instead of aluminium slude and scale?...

Step 4: Flush the system every couple of years. Do not reuse
old
coolant.
...Probably except if you do this for a home central heating
system you reoxgenate the water and corrode the rads quicker
..except you can buy inhibitors at a prohibitive
extortionate price....

-Gary


On Sat, 2004-10-30 at 07:17, Mark Shepherd wrote:
> How can the state of a rad be proportional to its voltage?
> The state of a decomposing rad generally would be
determined
> by its core wall thickness.
> Its thickness would be determined by length of time under
> decomposition.
> Rate of decomposition due to the battery effect would be
> constant for any given rad/coolant(electrolyte)
combination
> irrespective of rad size.
> Quantity of ally disolved would increase with rad size.
> Its my opinion (which may count for ziltch) that any
voltage
> across the rad could appear almost from the beginning of
> use (unless there is some kind of protective coating or
> substitute stick of sacrificial metal... perhaps zinc????)
>
> I think my resistance test would be more accurate  but I'm
> not sure if a dry rad would be better unless the state of
> the coolant/electrolyte was known exactly. What we need is
> two radiators one brand new and one leaking due to old
age.
>
> I wonder if earthing the radiator would stop this
corrosion
> by electrolysis?
>
> Miser