OK, I'll ask again. Please excuse my non-professional interest.
Photo Metrojet Airbus A321-231 EI-ETJ
This link posted previously, seems to show something that may be related to the loss of this aircraft (corrosion or fluid leakage?). Or doesn't it?
Perhaps someone familiar with the maintenance might care to comment?
The marks on the bottom of the rudder and fin are made by Skydrol, a phosphate ester based hydraulic fluid, which is really good at stripping paint and softening some plastics. It will also corrode titanium when heated. It is really evil cr@p to handle. The tail surfaces on the A320 family are carbon fibre reinforced plastic (CFRP). It's highly unlikely the amount Skydrol affected paint on the aircraft in the picture is enough to cause a structural issue, it just doesn't look appealing. You will probably find that the leak rate on the rudder actuator that has caused this paint stripping is well within maintenance manual limits.