It’s all too easy to assume the mast, boom, spinnaker pole and, where fitted, rigid vang of a yacht are items with an almost infinite lifespan. Granted, at some stage many owners will opt to maintain the cosmetic appearance with a comprehensive paint system.
If you opt for this route don’t be tempted by a quick paint job as these invariably do not last well. In any case, given the expense in removing the rig, surface preparation, masking and so on, it’s always worth the extra up front investment to do the job properly, including proper etch primers and decent epoxy based paints.
However, the bigger concern with spars is a structural one, with the key issue being corrosion that can happen with few, if any, external indications. The problem here is with the many stainless steel fittings that are riveted to the typical aluminium mast or boom. These two metals are relatively far apart on the galvanic scale, meaning that there’s lots of potential for corrosion if they are not kept apart electrically. Unfortunately it’s the alloy of which the spars are constructed that will fizz away.
Keep an eye open for any white powder forming around fittings that are attached to the spar. This powder – it’s basically aluminium oxide – is a product of corrosion and you can be assured that, if the fitting is removed, a much greater area than expected will be damaged.
If there’s any risk of the structural integrity of the spar having been damaged it’s vital to have it professionally inspected as soon as possible. In many cases even quite advanced damage can be successfully repaired through welding or internally sleeving the spar in the damaged area.
If you add any new fittings to the mast it’s important that they are not in direct contact with the spar – monel rivets should be used and the fitting should ideally be separated from the spar with a plastic shield. Failing that a barium chromate or zinc chromate paste such as Duralac will help to keep the two metals isolated.