alloy has great corrosion resistance as long as the tough oxide outer remains unbroken. if anything is wearing this layer off the corrosion can get a good hold. on my nacra 5.2 the jib halyard has a small block on the bottom end for luff tensioning. if the boat is left on the beach with the jib halyard ready to raise the jib that small block is up against the mast just below the mast hound and by moving around against the mast will wear off the oxide layer and promote corrosion. also on the boom i found pitting corrosion where stainless had been riveted direct to the alloy. after drilling the money rivets the pitting corrosion drilled out with little diamond bits and a dremel, then bright alloy was painted with a thick layer of anti-rust primer, then silver paint, then alloy tape and the stainless riveted back on with stainless rivets.

probably not the perfect method but all the materials were easily on hand, the job was simple to do and anything is better than doing nothing! pics attached