alt.energy.homepower

wrote in message
news:faucme$k9e@acadia. ...
> daestrom wrote:
>
>>A general rule to reduce corrosion is to use water that has a low
>>electrical
>>conductivity and not connect dissimilar metals. So if you use an Al
>>radiator, you might consider using short sections of hose to connect it to
>>copper piping. This helps minimize forming a galvanic cell that will
>>corrode the metal with a more negative potential.
>
> We can do that, but mechanics say an electrically-isolated aluminum
> radiator
> with rubber hoses and insulating brackets can still corrode (oxidize?)
> soon,
> with nothing but water inside. My old boy scout canteen ended up heavily
> pitted with white crud on the inside. I think this was oxidation vs
> mineral
> deposits or galvanic corrosion, since there were no other metals involved.
>

Quite right. Al forms a nice oxide layer that inhibits further corrosion,
*BUT* that oxide layer can be interrupted by several things. Physical
abrasion is an obvious one, but to a lesser extent erosion from very fast
moving fluids (sometimes called 'flow-accelerated corrosion'). But I don't
think you'll have trouble there.

The minerals in the water can have an affect too. From what I've read, any
with halogens (chlorides, flourides, bromides, etc...) will cause rapid
pitting of the surface. Carbonates (CaCO3, Mg2CO3, .) are not so bad.
But this ends up being you either have 'bad water' or you don't. Oxygen
also plays a part and you're drain down system will have some problems with
that (each night the wet surfaces will be exposed to air, each morning
re-wetted).

I've also read that there are dozens of different alloys of Al with
different corrosion resistance. No idea what version a radiator would have.
It may be significant that the interior is protected by anti-freeze with
corrosion inhibitors and the outside (exposed to rain, road salt, and storm
water) is protected by paint.

daestrom