Xantia door jam corrosion

[citroenxm]

It gets in and is trapped between the outer piece - IE the outer sill cover, and that inner layer... the water sits there - the rest is as seen... But as for getting in... hmmmmmmm watch this space.

Ill get some more pics from the next car and forward my theroy.......

[Citroenmad]

If you feel like cutting up to the door latch holes or finding if its part of the same sealed section, feel free

[Xaccers]

The edge of the outer sheet isn't welded, instead it's welded slightly further back, so water has a gap to get in. Over the winter etc this pushes the gap open more and cracks the paint allowing it to rust from the edge inwards.
Where water works its way in between the two sheets is where it rusts, so the open space which is able to dry out doesn't stay wet for long enough.
Some cars were welded better and so don't suffer as much if at all.

Cassy has it quite bad because she's had a knock in that area which opened up the seam more.
I was thinking of grinding off all the rust, treating it and then using aluminium mesh and resin to build it back up.