Interesting... the one I was referring to is Issue 2. Issue 1 seems more reasonable.
Issue 1:
CASA recommends that if engineers or aircraft owners are concerned about
and / or suspect possible internal corrosion on tubular structures to consult with a specialised NDT person
Issue 2:
Aircraft operators should ensure that the maintenance program for an
aircraft constructed from welded tubular steel structure includes a
requirement to periodically inspect all external and internal surfaces of the
tubular structure. Any approved maintenance program which does not
include a periodic inspection that will detect corrosion in the structure may
be considered inadequate