During an inspection of the windshield bolts on a Cessna 525C Citation CJ4, white dust was found around one of the holes.

White powder at a fastener is aluminium oxide working its way out — corrosion that has already started underneath, where nothing shows on the surface. Opening the area up confirmed it: corrosion had spread between the cockpit skin and the structure behind it.

The cockpit skin was replaced left and right, along with the crown and the upper and lower zee and zil behind it.