Aircraft maintenance guys use Alodine to passivate interior aluminium surfaces. But it needs to go onto bare metal. What you seem to have is corrosion undercutting the painted finish, which may be a problem.
Read about it here:
Return to: Caravans, Motorhomes & Trailers
We purchased our caravan from Caravan and Outdoor Centre Pinetown in November 2017 and have recently noticed an external corrosion of the aluminium cladding, which is very concerning as it is spreading and the van is relatively new (see pictures attached).
I would appreciate any advice as to the way forward.