this is a from of corrosion caused by a current flow generated between two
materials with greatly differing electrical potentials. Contrary to popular
belief, galvanism does not occur just between two different metals; it can
occur between other materials, such as carbon rubber and a metal. Carbon
rubber mated against aluminum, for example, is a disastrous combination that
will destroy aluminum very quickly. This is often found in carbon rubber
hose joined to aluminum or copper pipes and is often referred to as
electro-chemical degradation (ECD)

hope this helps answer the question.
Chad~

On Nov 28, 2007 12:26 PM, Zoltan Kuthy <zolo@foxinternet.net> wrote:

> I have always wondered, why would there be extensive aluminum corrosion
> built up under rubber hoses on aluminum parts or under the head gasket.  I
> don't see any electrolysis activity going on under such insulating material.
>  I am baffled.
> Anyone has an acceptable scientific explanation?  Or is it something
> everyone knows except I.
> Zoltan
>