Recently someone posted that they had their coolant lines (engine to rad)
replaced with stainless steel ones. It made me think about corrosion and
electrochemistry (arggh!), and while motives are not to alarm or criticize
other people's solutions I thought I'd post the following points.

While the various stainless steel alloys are rated quite passive on the
Galvanic Series scale, lying between Silver and Nickel alloys (Platinum at
the top - most noble - cathode, Magnesium at the bottom - most active -
anodic), it is only because they have a protective oxide layer. When this
layer is removed, Stainless becomes more active and falls between Lead and
Cast Iron on the scale.

The inside of our van's cooling system is anoxic, so presumably any
stainless in that environment would corrode at a rate not much better than
Cast Iron.

I'm sure boat owners on the list are aware of the strange behavior of
Stainless steel, seeing rust on sections of the same bit of steel, the rusty
areas only differing from the rest in that they are oxygen deprived (by
dirt, grease etc.) It is also known that stainless steel alloys are far from
perfect in below waterline use.

I won't go into the problems of dissimilar metals, except to say that a
stainless bolt in an aluminum plate will last a heck of a lot longer than an
aluminum bolt in a stainless plate (all in an aqueous environment).

Back to the stainless coolant pipes. While I don't think they are a great
advantage in preventing internal corrosion resistance, they probably do
resist corrosion from the outside in.

Alistair