Hi Darick,
Good to see you again at Oshkosh.
The only way to delay intergranular corrosion is to completely seal
the surface of the part from moisture. Impurities introduced into the
metal during the extrusion process become tiny anodes and cathodes,
and all that is needed is an electrolyte to start the corrosion
process. This electrolyte is moisture that works it's way in through
any pores in the metal. Sealing the metal surface with epoxy primer
works well. Zinc chromate DOES NOT seal the surface, so do not rely
on it.
I showed pictures of fuel tank rivet corrosion during the Ercoupe
Maintenance Seminar, which were hard to see due to the light coming in
from the sides of the building. I'll post those pictures soon for all
to see.
Syd
On Aug 3, 2009, at 8:03 AM, [email protected] wrote:
Syd did an excellant job of explaining intergranular corrosion at
the Oshkosh table, plus alot of other topics I'm sure. It's great
to have that talent in our group.
One question I forgot to ask...how can intergranular corrosion be
delayed? Is there statistical evidence that it is happening more
frequently? Is there a "useful life" we can expect to see in the
spars? Are we soon approaching this time?
I'm thinking this will be more of gut feel answer than anything
else, but I'd still be interested in everyone's opinion.
Darick
