Just finished mine;
Doug, Just finished my mast and can give you some help here. You didn't specify what your boat was or what year it is but most of the painted masts from the late seventies to mid eighties were supplied to Hunter by Kenyon Spars. The previous post is somewhat misleading and incorrect in that the mast is not treated. The painted Kenyon Spars are made of 6061T6 aluminum which does not require passivation. In other words it is not anodized, just painted. It's oxidation actually prevents it from corroding by forming an oxide that is hard enough on the surface to protect the sub surface metal. Painting will certainly help but it has to be done right. If you want a quality job you need to completely strip the mast to bare metal, prime with quality primer specifically for aluminum, Koropon is a two part primer used in the aerospace industry but some industrial primers will work as well. I then used a Awlgrip two part epoxy and applied four coats. It came out great and looks better than new. As far as fittings and attaching hardware to your mast is concerned, crevice corrossion is a very vague term and does not typically occur where stainless and aluminum come together. Stainless is a far more noble metal that aluminum and will cause galvanic corrossion if not insulated from the aluminum somehow. The best way to accomplish this is by using red Locktite on all the stainless fasteners going in to the aluminum during assembly. Also isolate stainless hardware from direct contact with aluminum by placing a plastic tape between them or using silicone to act as a gasket between them. All the aluminum surfaces should have paint on them where they contact dissimilar metals or galvanic corrossion from dissimilar metals will occurr. Just to set the record straight about crevice corrossion in stainless steel, it typically occurs intergranularly within the metal itself and is excacerbated by anerobic conditions. It is not a result of dissimilar metal contact. It is worse in the cheaper grades, 200 and lower 300 series as the nickle alloy is less. Therefore, use 304 or 316 stainless to eliminate the problem and keep all your fasteners where they can breathe. Don't cover with silicones or epoxy as they will eventually dteriorate. One last note, stainless gets weaker in tensile stregnth as the alloy goes higher so keep this in mind. A 304 stainless is a good choice and is typical for marine use. Also known as 18-8 stainless. Tom
