Mine are poor around where the machine screws go into the pillars so it’s obviously chipped the paint finish (whatever it is) and water gets underneath oxidising the ali, flaking the paint
I just mix up a bit of Humbrol modelling enamel using silver and a bit of gloss black and white and paint into the bits where it’s chipped off
It’s not a permanent solution as the ali will have been oxidised but it seems to be keeping it at bay
A more thorough way might be to put an etched primer for ali on first when touching up
