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WillS 11-09-2000 04:10 PM

Electrolysis / Keel stepped mast
My wife & I recently purchased a beautiful 1985 34 ft. Seidelmann Sloop. We have named her "MATCHMAKER", but that''s a story for another time. When we un-stepped the mast for transport (keel stepped), We noticed that the keel end of the mast has significant pitting that looks to me like electrolysis. The paint at the mast foot has also deteriorated. The marina foreman says the mast is still OK but looks like it hasn''t been removed for years. The mast step is an aluminum plug and is wet with only an inch or two of accumulation.
Is there a way to stop this action for good, before I have to trim or otherwise repair the mast? I plan to re-paint the mast end. Will adding an electrical ground to the mast and step leading back to the engine help? How about "Never-Seize" on the step?
Any help would be appreciated.

toribk 11-12-2000 04:03 PM

Electrolysis / Keel stepped mast

I experienced the same thing on my 1985 S2 27 and although the mast and keel plate were both aluminum, the mast pitted and had to be trimmed 1/4 inch to get rid of the pitting, actually small holes wearing through. I believe it is caused by an accumulation of salt air over the years, water from mast leaks and condensation and yes, some type of electrolysis between the opposing metals.

I corrected mine by placing masking tape around the mast 1/4 inch from the bottom as a guide and trimming off the bad section using a sizzler disk on a grinding wheel. If you have a steady hand, the cut is perfect and very clean. Next, I painted the inside of the mast with three coats of Awgrip and removed the keel plate to clean it with a high speed wire brush. When all was done, it looked like new.

As to how to remedy the problem from ever happening again, I''m just as puzzled as you and hope someone out there with a degree (laugh) can help us both. GOOD LUCK!

paulk 11-12-2000 05:05 PM

Electrolysis / Keel stepped mast
Sounds like you''ve got a corrosion/oxidation problem caused by salty bilge water in contact with aluminum. Careful sanding & surface preparation, followed by a coat or two of paint should fix it. Electrolysis is a little different, caused by electrical currents. If you do have electric currents running through your bilge water, wiring everything together will make the problem worse, not better.

WillS 01-08-2001 06:33 AM

Electrolysis / Keel stepped mast
Anyone have new ideas? Spring is coming and solutions are unclear!

navtron 01-10-2001 10:00 AM

Electrolysis / Keel stepped mast
You know metals corrode...even same metals...clean mast & mast saddle...heavy coat with epoxy paint on both...apply very heavy grease to mast end and saddle...drill small drain hole at bottom of mast just above saddle. Install mast. Water can now drain and you can spray in WD-40 to flush out contaminates and coat inner mast from time to time..

noctaluca 01-13-2001 12:13 PM

Electrolysis / Keel stepped mast
I have had same problem. The cure is to clean mast paint with two part epoxy paint, then keep the water away from the area. Instal a bilge pump that keeps the water to the absolute lowest point. Holes permitting water to leave the mast are also essential. By no means would I use Never Seas below water line or in wet areas(or grease). When submerged and wet this can actualy create a voltaic cell when sanwiched between two metal surfaces(even if similar metals). Also, if you use a wire wheel to clean aluminum, do not use a steal wire wheel. Small amounts of steel will always imbed into the aluminum and eventualy rust!!! Use a bronz pad or sand paper!

WillS 01-13-2001 05:19 PM

Electrolysis / Keel stepped mast
Thanks Bill, Navtron and all that sent suggestions.
I appreciate the great info.
I think part of the ongoing problem is that I can''t keep the saddle and mast base dry. The saddle is at the very bottom of the bilge. An 1/8 inch of water wets the base of the mast. I''ll clean, paint, keep the bilge as dry as possible and keep an eye on things.
Thanks again.

noctaluca 01-14-2001 08:34 AM

Electrolysis / Keel stepped mast
Just an additional thought.
I use a electric fan dryer to keep the boat air dry. It is sold by West Marine and called the "turbo dryer". I run it year round 24 hours a day. It has worked now for 5 years straight! It keeps the moister in the boat to almost nill. Consequently, there is no mold smelling things growing in the cushions and nooks/cranie''s (nautical term!). In addiotion though the bilge stays bone dry. I pull up a few floor boards and the 1/8 inch water you speak of dissapears. I do however have a shaft log that does not lead much. In winter when I do not use boat much I tighten it down a bit more than usual.
Good luck,

munchimike 01-19-2001 03:27 PM

Electrolysis / Keel stepped mast
AHOY!!! Treat your mast step like any other marine installation; forget trying to keep it withit.Zinc chromate two part primer, drain holes in step, them bed the entire thing in Dolphinite till it squishes out all over the place, grounding plates from your chain plates to the keel bolts on the outside of the hull.......not in the bilge...Rev. Mike

Soliloquy1 06-25-2006 08:44 PM

I have the same problem with my new 1985 Oday 28. The thru hull fittings and bronze seacocks were all bonded together and to the mast plug. The bronze is like new and guess which is the "zinc"?, yep, the aluminum mast and mast step. Don't bond these together, the aluminum will suffer for it.

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