Had the same problem on my Pearson
, steel step in the bilge
with aluminum mast sitting directly on the steel. I had to cut 3" off the end of my mast where the Al corroded away.
I started with a 3" slab of UHMWPE to get back the 3" I lost
on the mast. The old steel step was attached to the keel with 4 lag bolts. I bought 4 bronze lag bolts 3" longer to attach the UHMWPE to the same spot. Took another 2" slab of PE and cut a hole in it to match the mast shape and attached that one to the base with 16 bronze screws to make a socket to hold the mast.
I was be concerned that the movement of the mast would gradually wear through the UHMWPE so sandwiched a sheet of 6061 Al between them for the mast to sit on. Be sure to isolate the Al from all of the bronze fasteners or you will have an electrolysis
Also make sure you cut drain channels in the mast base and in the step so the water
that will get in there can drain.