On 24 May 2007 06:42:50 -0700, Todd wrote stuff
and I replied:

This does not sit well with me. I thought that localisation was why
stainlless screws ended up in powdered aluminium and came loose. The
way I learnt it, the actual corrosion was across the boundary of the
two.

The stainless is more noble than aluminum, hence the stainless will
corrode the aluminum. But, since the bolt is so small compared to the
mast the damage done by the corrosion will be very, very, very slight
and the damage will not be localized at the hole, but over the entire
volume of the aluminum. At least, that is what I've been told and how
I've done similar work on my mast. Use the goo though.