[Douglas]

I agree with what Renoir replied , but I am at a loss to understand, as to how corrosion begins under a proper undercoat and then top coat of paint on an aluminum spar.

One person I talked to said, that even a finger print, or , a high humidity condition , on the preped aluminum surface, before the undercoat is applied, could and can , cause corrosion under a painted surface on an aluminum spar ???

Could it be that the undercoat and top coat of paint is porous enough to allow ingress of moisture which accelerates a corrosion problem and then is evidenced on the surface ?

Another question is, if UHMW tape is applied over a potential corrosion problem spot , could that tape reduce the corrosion potential at that spot ? Especially at the mast butt to mast step area ?

On my Forespar mast , I found an enlargening corrosion spot under the LPU painted surface just above the dining table inside the cabin. On closer inspection , I found a horizontal joint line in the sailslide groove, which is where the corrision seemed to start from .

From this inspection , I assume that Forespar, welded , aluminum mast sections together, to make a longer stick , and that the joint itself was contaminated and allowed the corrosion to break out under the paint job on top of it.

I had the mast carefully, glass bead blasted with un-recycled beads, then the Alondine prep, before the Algrip primer and top coat, but after 2 years, that surface corrosion began to show through, under the paint, and enlarged at that suspected joint !

I like it, that Brion Toss says, " try to build in a reserve of neglect" , when refering to rigging practices , but how can we best do this, when there is sooo much to know and look out for ???? I mean ,,,, all we wanted is to go sailing ,,,, right ????

Does anyone know if , powder coating is a better option to fight against corrosion than proper surface painting on a mast and boom ?

Douglas ,,, frustrated in a corrosive world !