unforgiving stainless....

[Rockter]

Enough to chill you to the marrow.

Leave is short on oxygen and give it some chlorides from seawater, and this is what you get.

Have a look at the video at around 3.20...

replacing Tayana 37 chain plates - YouTube

In the spring, I will look at mine. I've got 6 of them on the sides of my ship, a Union Polaris 36. Last time I looked (about 12 years ago) they were OK. I will have to look again.

Note where it is oxygenated, it shows no distress, and very little corrosion. Where hidden, and wet, and de-oxygenated, and chlorinated(?), it rots like biscuit.

Rockter.
.

[Capnblu]

Imagine the corrosion that guy will get with stainless, and cold rolled steel, just in the humid environment!

[StormBay]

When we recently bought our boat (1985 HC41) we found 5 cracked chainplates, one cracked whisker stay and most of the bolts And nuts for them crumbled! After I removed some of the bolts, I was able to break them simply by tapping them on the vice (see video) though they looked nice and shiny when they were installed. scary is an understatement.. Stainless is evil!

Chainplate bolts Hans Christian 41 - YouTube



These are from one chainplate alone..

[StormBay]

Originally Posted by capnblu

imagine the corrosion that guy will get with stainless, and cold rolled steel, just in the humid environment!

+1

[Rockter]

Stormbay :

I have a Union Polaris 36.
Last time I took the chainplates bolts out (1998?), they looked fine, and the chainplates.
Stainless is terribly unforgiving if it gets de-oxygenated when seawater is around.
Those bolts and nuts you pictured are showing classic chloride attack. In the presence of oxygen, even oxygenated seawater, it simply does not happen.
But how the heck do we get oxygen into chainplate fasteners that are seawater wet?
One of my stern-plate bolts was eaten almost right through back in 1992. I will need to check those too, soon. Between tides will do it, I guess. This far north, 57 degN, we have big enough tides.

I will have a look at all of my chainplates in the spring.
Does bronze work better?
Do we need carbon fibre chainplates?

Right now, I am in freshwater, and have been for some time. Beautifully-clean Loch Ness freshwater too, if a bit "peaty". I notice that the bronzes adore it. Maybe I need to stay there?
.

[StormBay]

Rockter;
According to our previous owner our chainplates and bolts were also pulled and checked 2001 after cracks were discovered on the cransiron. According to him all looked fine and were cleaned and reinstalled. One of the biggest problems with our Taiwanese built boats tends to be the quality of stainless used on them which was more than likely not 316 (there was little quality control at the asian foundries at that time) On our boat, we can see evidence of this everywhere and have discovered hairline cracks throughout most of our original stainless parts (dye testing can help se what your eyes can not).

There was a compelling article in both Practical Sailor and another mag (can't remember witch one) regarding titanium for use in these situations. Titanium is lighter, stronger, doesn't suffer crevice corrosion, and is extremely noble (though that could be a bad thing as well) compared with stainless. The biggest down side that I can see is the fact that it remains pricey. The site that both articles pointed to for titanium parts and custom chainplates is Allied Titanium - Home Page (no affiliation ) It looks although they have both a Bobstay Plate (item 0035380) and a Bowsprit plate (item 0035379) on hand for a Union Polaris 36; I am sure they can make other parts as well.

[mitiempo]

It doesn't matter much if the water is salt or fresh - it is the lack of oxygen that causes the problem. Keel bolts have a salt water issue (in salt water regions) but chainplates mostly have fresh water issues as it is the rain and leaks that are the problem. The trick is to keep them dry where they pass through the deck.

[Rockter]

mitiempo :

Chlorides absolutely feast on chrome when there is no oxygen.
Below the water line in salt water, it is murder.
We cannot corrode without a reactant.
Fresh water really is far more forgiving.

[Rockter]

Stormbay :

I'd better get a crack testing kit.
This may get expensive in Titanium, methinks.

[SloopJonB]

Originally Posted by Rockter

Does bronze work better? .

In a word, YES. Bronze is the ultimate marine metal - the teak of metals

I have seen pictures of bronze bits pulled up from ancient Roman galleys that were almost as good as new - 2K years old and older, submerged in the Med the whole time.

Stainless is shiny pretty and it's more easily available as well as cheaper but bronze is better - prettier too if you can keep it polished but that's worse than maintaining varnish.