John (Killick), just to back up what Tom said, I had the rigging replaced quite some time ago. There was a lot of bubbling of the paint on the mast and boom and it looked like the spars were quite badly corroded. The rigger sanded off the bubbling paint and there is only a feint trace of corrosion on the now bare aluminium. I elected to not paint the mast so that I could see what the corrosion was doing. It has not come back and the mast is full thickness.
Greg.