I don't necessarily agree with this. Many engines since the mid
fifties have had aluminum Heads on Iron blocks with steel piping and
water pump shafts, along with copper heater cores and Radiators.
Without the need for Zinc electrolysis blocks. Our favorite Alpine is
an example, along with just about every other car I have ever had. The
potential IS there for the problems you mention, but the basic
water/glycol mix is a corrosion inhibitor, and even pure fresh water
(soft) is resistant to by-metal electrolytic corrosion. This is partly
due to waters neutral nature. Saltwater on the other hand is a failure
decent conductor, and would eat through the above mentioned engine
within a few months. Any contaminants in the water glycol environment
will begin to degrade this inhibiting factor, which is why flushing the
cooling system every year is important, although I never did it.
Simply put, you are not going to be able to have all materials
touched by water being made out of the same metal. You'll still
probably have some screws or bolts, and certainly the water pump shaft
made out of steel, so Dis-similar metals will always be present. If you
have ANY aluminum components, including timing cover, water pump
housing, Intake, heater core or radiator, heads or block, then you MUST
run a mix of pure water (bottled if you are in a hard water area), and
Glycol (anti-freeze) to reduce the electrolytic corrosion problem that
can happen as contaminants begin to enter the cooling system. Other
wise, corrosion will begin in areas of turbulence on aluminum. The
timing cover right behind the impeller is a typical spot for this to
happen.
Rich
> ----------
> From: Tom Ballou[SMTP:TBallou@lanmail.rmc.com]
> Reply To: Tom Ballou
> Sent: Tuesday, May 27, 1997 9:14 AM
> To: tigers@autox.team.net
> Subject: radiators and water chemistry
>
> I have been watching this radiator dialogue and attempted to interject
> some
> water chemistry considerations a couple of weeks ago, but was
> unsuccessful.
> Here goes again.
>
> Copper and aluminum are both excellent heat transfer materials.
> However they
> don't mix well. In fact, they are bitter enemies! When they are put
> together the result is rapid and destructive corrosion. Even when
> linked
> only by water in an engine cooling system, the result is eventually
> the same.
> Switching one component while leaving others unchanged can be bad
> news. An
> example is installing an aluminum intake manifold on an engine with a
> copper
> cooling system. I just pulled mine again this weekend in the course
> of
> disassembling the engine. I last pulled it about 15 years ago. Both
> times
> the water passages have been severely corroded- the result of
> dissimilar
> metal activity. Perhaps you have noticed a white or light grey sludge
> in the
> bottom of your radiator if you have some aluminum components - it is
> Alumina,
> the product we manufacture here, which is Al2O3, aluminum oxide. The
> white
> scale on the inside of the water passages is the same stuff. Alumina
> is an
> excellent insulator (makes great refractory and things like the heat
> sheild
> tiles on the scape shuttle), but doesn't transfer heat well at all.
> If you
> are going to switch some components, you need to think about switching
>
> everything - radiator and heater core (and thermostat). Otherwise you
> will
> have constructed a battery and the aluminum component will be
> sacrificial
> anode. Could be your intake, radiator, those expensive aluminum
> heads.
>
> See you in Eureka!
>
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