Yesterday I took off the left front outer fender of my Amazon, and observed the same phenomenon as on the right side.

While the mounting surface on the wing itself was in relatively good condition, the box section on the inner front fender (which holds the fender's mounting screws) crumbled completely even without touching it.

Does anybody have any idea while this box section seems to rust from the inside out? It has a drain hole in the front, so any water in there should run out of it. Is it because the inside never got a decent rust protection coat of whatever they used back then?

I noticed in the replacement panels that the inside of the box section seems to be unprotected, but my general impression of replacement panels is that they don't hold the quality that Volvo's original panelwork had.

Not surprised, just curious...