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post #1 of 11 Old 05-03-2012 Thread Starter
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Galvanic corrosion - sail slides

So here is the question, can stainless steel sail slides corrode the slide track of an aluminum mast?

I understand that SS can corrode aluminum, but in this case the slides will be touching or leaning against the mast, and not necessarily attached to it. Would that make a difference?

The slides are 3/4 internal flat (I've attached a picture). The reason I bought them (at a marine salvage) is because I thought they would make it easier to hoist my mainsail; their "waist" is flatter than those on plastic slides, so, in theory, they would create less friction in an internal slide track... But would they also create galvanic corrosion?
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s/v América
1974 Catalina 27
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post #2 of 11 Old 05-03-2012 Thread Starter
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Re: Galvanic corrosion - sail slides

Almost forgot... If corrosion is a possibility, how hard is it to "paint" or apply a PTFE coating to the SS slides?

s/v América
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post #3 of 11 Old 05-05-2012
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Re: Galvanic corrosion - sail slides

I would not use S/S slides on my aluminum mast. My fear would be the metal to metal contact. Stainless is a harder metal than aluminum and the possibility of the stainless steel wearing away any of the aluminum channel would be a concern. If a jam of the slide in the channel happens, the S/S slide could dig into or gouge the aluminum channel. IMHO, it would be better/easier to replace a plastic slide than to try to repair an aluminum channel.
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post #4 of 11 Old 05-05-2012
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Re: Galvanic corrosion - sail slides

Galvanic corrosion is very slow. Stainless steel is not a material for sliding which will cause a lot of friction (more than plastics) and will abride mast.
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post #5 of 11 Old 05-05-2012
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Re: Galvanic corrosion - sail slides

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Stainless steel is not a material for sliding which will cause a lot of friction (more than plastics)
Stainless is generally only used for the first 1 or 2 slides at the mast head where the stresses are greatest. The rest of the slides are generally nylon.

Galvanic corrosion is not an issue with the first slides because the sail is constantly being raised and lowered. In addition, the track should be lubricated yearly. Those two events will make corrosion a non-issue.

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post #6 of 11 Old 05-06-2012
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Re: Galvanic corrosion - sail slides

And anodized aluminum is less effected by stainless.
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post #7 of 11 Old 05-06-2012
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Re: Galvanic corrosion - sail slides

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Originally Posted by mdbee View Post
And anodized aluminum is less effected by stainless.
True, but the stainless rubbing on the aluminum will remove it.

Brian
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post #8 of 11 Old 05-07-2012 Thread Starter
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Re: Galvanic corrosion - sail slides

Thanks for the input, fellow sailors. I've decided to go back to nylon slides.

BTW, I've just read Nigel Calder's opinion about this in his Mechanical and Electrical Manual: "Only nylon sail slides should be used on aluminum spars, since metal will score the track and generate galvanic corrosion" (page 743, Third Edition).

So there you go: nylon it is!

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post #9 of 11 Old 05-08-2012 Thread Starter
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Re: Galvanic corrosion - sail slides

You are absolutely right, Chris. It's better to make the "weak link" the "cheapest past" as well...

s/v América
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post #10 of 11 Old 07-01-2012
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Re: Galvanic corrosion - sail slides

Can I add a comment ? In Aluminium masts with rectangular slots, jamming has always been a problem. The Rolls-Royce solution is the Harken system, which makes use of an aluminium, black anodised, track with a groove on each side. The track slides up the slot in the mast. ( The mast has to be unstepped, and the boom attachment and mast heel fitting removed, usually. The slides are re-circulating balls ( delrin ). Attach the sail with bronze or nylon shackles - do not sew onto the slides - because the slides stay on the mast. Trying to remove results in escaped balls - nightmare, v expensive. No jamming, sail drops instantly. Particularly if you use a 'dutchman' system ( eyelets in mainsail, so sail drops in neat folds. ) Lazy jack / sail cover catchers are more common in Europe, but get tangled hoisting. OR - use Proctor slides, ( best, because strong and no corrosion problem ) which are Stainless Steel, encapsulated in Nylon. Use with Silicone grease, obtainable in toothpaste size tubes. Plastic ( nylon or similar ) suffers from breakage aloft owing to UV + strong winds. To replace means taking whole sail out of groove - not easy with a boat like mine ( 45'). OR mill slides to suit your mast out of Glass Filled Nylon to a pattern similar to the ALLSLIP design, which has a running surface in both the inner and the out surface of the slot, like a letter 'H' ( H--) To attach the shackle, drill after milling. Use Black compatible paint to cheat UV light degradation, or Black GFN. For the ready-made items, Bainbridge International supply: East coast tel=1-781-821-2600, fx= 1-781-821-2609 West coast tel= 1-714-373-3322, fx= 1-714-373-3326 There are other solutions, but these best ( Harken ) or most cost effective ( Proctor type ) I have same problem myself - will post another message when I have solved mine. I prefer the idea of Dutchman sail gathering to lazy jacks, but sail covers less easy, also sail wear and air flow a problem, and corrosion of guide wires and UV degradation of coating. ( I take it all know dutchman system - vertical coated wires thru' eyelets in mainsail, so sail drops in a slatted pattern. ) I use lazy jacks, but stow them under way; and use a separate sail cover, very basic and cheap to renew. Hope this helps a bit.
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