----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----
Intergranular and dissimilar metal
corrosions can give rise to strange phenomena. We got back to
clean metal very quickly, yet the origination may well have been an interaction
between the bolts and the spar web. Manufacturing defects and fuselage
chattering may also have contributed. In all probability the problem was a
result of all three. However, with no further internal (bolt hole) or
external signs I'm inclined to submit the spar cap to regular inspection (it's
easy enough to do) and leave it at that. My reason for starting this
thread was to bring the subject up such that true problems, like the photos the
other week, are identified before they cause all owners problems with
AD's.
Regards.
Jim
-----Original Message-----Hi Jim,
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Tuesday, April 17, 2001 9:37 AM
To: [EMAIL PROTECTED]; [EMAIL PROTECTED]
Subject: Re: [COUPERS-TECH] Confusion and main spars
What you describe does sound like exfoliation corrosion. It has a peeling
appearance like an onion skin. Usually you can grasp a piece with
needle-nose pliers and just peel it right off the surface. I found the same
corrosion in my center section on the inside spar cap face just above the
main gear attachment bolts. I believe it is due to dissimilar metals. I
have heard of people taking the exfoliation off down to clean shiny metal and
repairing just as you have done. Would still require inspection and sign-off
by an IA, I believe.
Jim
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