Cause of rust?

[AdamBeevers]

Hi guys,
Im interested to know what causes the bulkhead to rot? Is it the sound deadening stuff in the engine bay thats stuck to the bulkhead or something to do with a possible drain hole i see on the battery tray?
Any information would be great.
Thanks,
Adam.

[harry_p]

Water collecting, seam sealer shrinking with age, and natural stresses you get at a high load point causing movement in the metal and micro cracking of paint and primers.

[Brianmoooore]

Bulkhead is double skinned, and rusts from the inside when the seam sealer along the bottom of the scuttle box fails. The first sign is often one of the studs that the glovebox attaches to falling off.

[AdamBeevers]

Thought it was double skinned, mines appeared to have gone on the drivers side (RHD). Very strange, inside my scuttle it looks mint! Not really sure how to prevent future damage if its double skinned...