Hi friends,
I know that stainless and aluminum react together and corrode. My otherwise useless surveyor pointed out a folding step fastened three feet above the bottom of the mast and suggested I remove it as I don't need it to attach the main halyard anyway. However, there are plenty of places where there are SS fasteners in the spars (mast and/or boom), and isn't there corrosion there too?
To be precise, I can see that there is indeed corrosion where the stainless loops holding the main sheet blocks attach to the boom with a stainless through bolt.
Should I remove the loops and remount them an inch or two away from the current location? What about all the other fasteners in my spars; should I periodically remove and reinstall each fastener with an anti-corrosion compound?
What about places you can't readily change that are high-stress, such as the lower shroud tang attachment points?
Thanks as always,
- nick
Nick Tonkin
*Former* Website Administrator, C36/375IA
*Former* owner, C36 tr/fk #255, Santa Barbara, CA
Nick,
If you have the time and inclination, I think taking out SS fasteners and reinstalling them with Never-Seize or similar would be a good thing. Not sure what to say about the lower shroud tang, though....
Tom Sokoloski
C36/375IA Past Commodore
Noank, CT
Hi Nick this is from Wikpedia;
For normal environments, such as storage in warehouses or non-temperature and humidity controlled environments, there should not be more than 0.25 V difference in the "Anodic Index". For controlled environments, in which temperature and humidity are controlled, 0.50 V can be tolerated. For harsh environments, such as outdoors, high humidity, and salt environments, there should be not more than 0.15 V difference in the "Anodic Index". For example; gold - silver would have a difference of 0.15V being acceptable
18% chromium type corrosion-resistant steels -0.50
Chromium plated; tin plated; 12% chromium type corrosion-resistant steels -0.60
Aluminum, cast alloys other than silicon type, cadmium, plated and chromate -0.95
[B][U]Note there was no figure for SS but the above would probably suffice for the information. My guess it is another reason to replace with a 316 SS srew bolt etc. which would bring you closer to a good match.[/U][/B]
Considering the age of your mast my feeling would be the same as Toms which is to use an anti seizing compund to reduce the galvanic action. I would also keep an eye on the high stress points. Tangs are usually the same as your boom bails, done with a through bolt. Tought that comes to mind is to sleeve the bolt with a headed bushing made of alluminum. Perhaps this is a good question for a rigger?
Gary Bain
S/V "Gone With The Wind"
Catalina 36', Hull #: 1056, Year: 1990, Engine: M-35
Standard Rig
Moored: Boothbay Harbor, Maine
Home: Auburn, Maine
Thanks Tom and Gary, most helpful. I had a rigger on the boat yesterday; he, too, suggested nylon washers and plastic sleeves as well as anti-seize compound.
Nick Tonkin
*Former* Website Administrator, C36/375IA
*Former* owner, C36 tr/fk #255, Santa Barbara, CA