SST as anchor material

[Alan Wheeler]

Due to some "noise beyond our control" this question got rather lost. I will start this question again on behalf of Trim50 and post the few responses.

[Alan Wheeler]

Quote:
Originally Posted by Pblais
Stainless Steel anchors look great on the bow and stay nice and shiny. They are not as stong and are subjet to crevice corrosion. If you don't anchor much it's great because they look so nice at the marina.

OK, lets talk about stainless steel and alternatives. What steel do you suppose is better in salt water than 316?
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[Morgan Paul]

How about Monel ?

[ssullivan]

Originally Posted by Alan Wheeler

Quote:
Originally Posted by Pblais
Stainless Steel anchors look great on the bow and stay nice and shiny. They are not as stong and are subjet to crevice corrosion. If you don't anchor much it's great because they look so nice at the marina.

OK, lets talk about stainless steel and alternatives. What steel do you suppose is better in salt water than 316?
__________________
Fall is my favorite season in Los Angeles, watching the birds change color and fall from the trees.
David Letterman

Trim Blog

I would think the metal you use is most dependent on the type and length of anchoring you do.

If you're anchoring overnight here and there in sandy bottoms, why not a stainless anchor? Looks pretty, easy to clean off, etc....

However, if you do like us and bury your anchor for a month at a time in mucky gunk with little O2, it would seem stainless deterioration from lack of O2 could become an issue.

I have no scientific facts to back this because I'm too darn lazy to look all that up and post it here, but my 2 cents is that it would depend a lot on how you plan to use the anchor.

[Alan Wheeler]

Firstly, SST is an Alloy of several different metals. The key ingrediant to corrosion protection is Chromiuim which produces an gassious oxide on it's surface from contact with oxygen. That layer then stops the oxygen from contacting the chromium and further oxidising it.
There are many different types of SST, with 304 and 316 being the most common that us boaties will come across and the main difference between them is the Nickle content in the steel.
Intense heat will change the Alloy structure within the SST "mix" of metals. Welding is one of those heat sources. The change in the molecular structure of the SST when it is welded can cause an area of "dissimilar metal". This is the same as any situation on a boat where you have dissimilar metals touching. The result is galvanic corrosion. In SST, this area of metal difference is very thin. So a corrosion called crevice corrosion starts to occur. This creates a "crack" between the the Parent metal and the Weld metal. The crack can be microscopic and the only time you find out it is there, is when the metal finally breaks apart.
A one piece cast SST item is close to bullet proof. The Bruce anchor in SST is one of those that can be trusted. They are cast as a one piece item. Ploughs are another that can be trusted, as their two main parts are often poured as one piece. The spade design (if available in SST" would probably be OK, as the two sections are bolted and the bolts are no intergral in keeping the two sections together. The ones that are not so trust worthy are any that have the shank and the fluke welded to each other and where that main source of strain is seen across the weld like that. Now ion saying that, several factors can be applied that will make these area's of possible failure a little less possible. Carefully and properly laid welds that have deep penatration and multiples of those welds. This results in the contact area of Weld and parent metal being broken up. One giant weld, although looking great, would have one contact area. The weld needs to be carfully Passivated, ground and polished. The polishing results in a high concentration of the harder Chrome coming to the surface. It also removes the fine scratch marks where crevice corrosion can start working from. And finally, an anchor is usually made from a fairly heavy lump of materials. It would take a great deal of time to work all the way through to the point of failing. Plus to add to that, the anchor is not a permanant mooring. It doesn't sit in Salt water all the time. Hopefully a great deal of the time it is going to sit up on the bow.
So to sum up, I am happy with my shiney SST anchor and I trust it. It is light weight for it's size which has made an enormous benifit with the way the bow rides up. Plus it means I can now carry mor chain because of the wieght saving. I would trust any production anchor. They look good on the bow. As long as you inspect the anchor on occasions, you shoudl be fine. You should be inspecting your anchor, chain, and winch once a year anyway.

[44'cruisingcat]

I'd possibly buy a cast SS Bruce if I won the lottery. But failing that there are higher priorities for the budget.

[AnchorageGuy]

I am not sure that failure of a stainless anchor is as big of an issue as the fact that after you anchor a few times and the finish develops scratches they start to look pretty bad with the rust streaks. So you have lost that pretty appearance. The SS anchors we see on th docks are attached to the boats that only stay at marinas and would only drop the anchor in an emergency.

[Trim50]

I have two stainless anchors...use them lots. I had a galvanized steel anchor for many years and it was always rusting.

[Sandero]

My galvanized CQR is rusting at the edges of the flukes I suppose from "wear". Not pretty but has little effect on the anchor.

SS anchors are strong enough, but too expensive. I haven't seen them on cruising boats which use their hook a lot so don't know how they would stand up. The scratches would not bother me after the first few.

[Alan Wheeler]

as the fact that after you anchor a few times and the finish develops scratches they start to look pretty bad with the rust streaks.

Mine has not scratched, but then we do anchor in softer sediments. It certainly has no rust. No SST anchor should rust. I would be immediately concerned if it was rusting.