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wsmurdoch · 01-05-2019, 15:23

The titanium shackle or swivel may strip off the zinc on nearby galvanized steel then attack the steel, both by galvanic corrosion. You would not think of mousing a galvanized steel shackle with copper wire, and titanium is much farther up the galvanic series in seawater than copper.

I would not mix titanium with galvanized steel.

Bill

**a64pilot** · 01-05-2019, 15:34

Quote:

Originally Posted by Dockhead

Keep in mind that Ti is x% stronger than steel only BY WEIGHT, not by volume. To make a Ti shackle which is equal in strength to a given steel shackle, it will need to be rather larger than the steel one. For it to be stronger, it will need to be a lot larger. Since size is what usually constrains us (getting the pin through the chain end link) Ti seems unsuitable for this purpose. We want as much strength packed into as little volume as possible. And the weight -- and weight is the one really great advantage of Ti -- of the shackle is irrelevant, connected to a quarter ton or half ton of anchor chain.

As to that swivel -- that's the type that can't handle lateral loads.

And would kind of galvanic corrosion issues would you have, with such an unlike metal immersed in sea water between two steel parts?

Personally, I don't like any of that stuff. Stick to tested "colored-pin" galvanized shackles, as far as I'm concerned.

Titanium IS stronger than SS. Number I was given for my chainplates was 300% stronger than 316L SS, identically dimensioned. Although as there are different ways to determine “strength” that number will vary.
Ti is more noble than almost any other metal, so it’s unlikely to cause any corrosion issues, I have SS pins in my Ti chainplates as do others with Ti chain plates, with no issues.
Actually that statement isn’t true, Ti is extremely reactive, it will if scratched create an oxide layer that protects the rest of it within milliseconds, once that coating is formed, it’s Noble, but forming that coating is faster than you can blink your eye.
We have a member, Stumble I believe that can discuss the merits of Ti with a lot of knowledge I believe.
However in aircraft construction, you have to take care that no Cadmium plated steel hardware comes into contact with Ti, but I know of no other dissimilar metals corrosion issues.
Cadmium plated tools were not allowed to be used on the SR71 for instance.
The use of Ti isn’t new by any means, it’s been around longer than I have and is an extremely common metal, just apparently newer techniques for refining it have made it more affordable.
I’d go as far as to say that we will see in our lifetimes the near extinction of SS in boats, replaced by Ti.

Ti isn’t a perfect metal of course, I doubt you’ll ever see a Ti crankshaft, or a racing motorcycle chain although with its strength to weight ratio, it would seem perfect, but it sucks as a bearing material, it smears I’ve been told.
It’s also a Bear to machine.

Ti’s greatest strengths in Marine hardware is its strength and extreme resistance to corrosion, resistance to fatigue. Lightweight is way down on the list.

However before using it with zinc coated chain, I’d make sure that zinc won’t cause the problems that apparently Cadmium does.
http://www.eaa1000.av.org/technicl/corrosion/ticad.htm

**a64pilot** · 01-05-2019, 15:48

Quote:

Originally Posted by Dark Horse

Agreed. A swivel is another failure point. Not needed. If the anchor comes up backward I will deal with it. Much better than dealing with a swivel that let go in the dark, in 45 knots of wind with the rain in your face.

Let’s see you bust this swivel.
I don’t think you can, even with G70 chain.
https://www.mantusmarine.com/mantus-swivel/

There are many junk swivels, my boat came with one, but there are a few good ones too. Not many though, and they do cost more than the junk ones