New O'Day 30 Owner ... just now starting to go over the entire boat ... have aquick question!
What's the best recommendation for "slowing" corrosion that has started at the foot of the mast? I have always been told that painting this just traps moisture and expedites corrosion?? Any good ideas...!?
I've been there and done that, believe me. I don't know if there is an easy answer to your question because there may be too many variables involved like stainless steel and Aluminum in close proximity of one another. This was what caused the demise of the bottom portion of my Z-190 (Z diffusion, Z-Spar) Mast. I wound up having to cut 2" off the bottom of my mast last year.
This all started back in the mid 1990s when I lost my mast out off of Newport RI. The boat was insured and I had a company in RI called Rig-Rite rig up a new Z-Spar mast for me. I didn't want that cheap French made cast Aluminum tabernacle that originally came with my mast. I wanted a stainless steel hinged tabernacle which I always thought was a Kenyon but turned out to be a Dwyer hinge. Maybe the utility plate was a Kenyon and I misunderstood.
Anyway, the rigger at Rig-Rite had to fabricate a mast plug out of Stainless steel for my mast in order to make this hinge plate work. Here lies the problem. I really have no idea if the rigger ever used anything to insulate the two unlike metals. The plug was held in place by five stainless steel machine bolts through the sides of the mast which caused the holes in the mast to corrode and get enlarged about 10 years later.
I brought my mast to a marine welder and he did the best he could but he told me that the inside of the mast is thin and corroded.
To make a long story short, I wound up cutting 2" off the bottom of my mast and I had to use two pieces of Trex and the same S.S. mast plug to get me back on the water. This was just a temporary fix. Trex is too heavy for a mast extrusion I think, so last spring I made up an extrusion using a piece of 1/4" Aluminum plate, one piece of 1" Trex, for the plug, and some PVC trim board. The top Dwyer hinge plate is bolted to it with for bolts.
I think that water plays a big part in corrosion. I made provisions on this mast plug so that water can drain out of the mast. I insulated the s.s. screws that secure the plug to the mast with nylon washers and a small dab of Never-Seize on each screw.
I don't know if anyone else has ever constructed a mast extrusion out of these materials. Capt'n Pauley came up with a solution for something similar to this which involved using StarBoard or HDPE on top of a cabin to be used in place of a cast Aluminum mast step in which the bottom of the mast sits on. Mine of course is a whole lot different than his.
All I know is, so far so good. It works. If I had neglected it any longer, the bottom of my mast would have blown out on me and I would have lost another mast.
Last year before I made the temporary fix to my mast, I trailered my boat to a marine fabricator on the river. The guy hemmed and hawed and said that he would need to cut 2" off the bottom of my mast and find a piece of mast similar to mine that could be welded in place with aluminum reinforcement on the sides at,--$300 an hour.
I told him I'd think about it.
I was back on the water in less than two weeks and it only cost me some time and pennies. I didn't know it at the time but his company was going belly up. "Nice try pal but I think I'll pass this one up."
At some point in time we need to remove the mast plug or casting in order to access wiring in the mast. I'd check out the inside to make sure of the thickness, make provisions for the mast to drain out if water get in, and use some kind of insulating compound between the metals. They have some stuff on the market that is used for this purpose.
