Boeing wing upper skin was normally painted with an extra heavy coating that I think I remember was called corogard.
I was taught that in the beginning of jet transport, the early B707 era, corrosion protection was the same as for piston aircraft of that era- chromate and not much else. This was OK for the piston engine era because aircraft were retired quite early because they vibrated themselves to bits.
....So after 10+ years the early B707 were still flying and then corrosion started to be a big problem. Under galley and toilet areas - the infamous blue ice incidents and in the bilges. That lead to a major upgrade in corrosion protection.