of all those things should be done in fresh water
each time you come in from a sail. Simply fresh water
. You can't do much with Anodised Ally.
If there is piting and a white powder is present, then the damage has been done. You can not restore the damage. Especially if the anodising has been damaged. You have to inspect the mast
very closely. If the white powder/corrosion is set into this, it is in need of urgent work
. The only way to get rid of that white powder is to wire brush it off. It will leave pit marks. But if you have this problem, then it will most likly be somewhere you can't see as well. Like under fittings and tangs and so on.
Jef, this could be seriouse, so can you post a photo
of the problem or at the very least, give us some finer detail of what your situation is. We maybe able to give you some detailed advice for the variuose components as against an over all blanket approach.