Chainplate replacement question

[coopec43]

Originally Posted by Toccata

I have replaced several sets of chainplates on old yachts.
My take is: Don't forget to replace the bolts as they too suffer crevice corrosion, particularly if there has been any leaking through the deck.
I chose to weld the cover plate. I fitted the chainplates, then scribed a mark at deck level, I then set the plate 2mm above the deck, to allow for a decent layer of sealant. No screws through the horizontal pate so force transfer to the deck probably nil. The weld was of minimal penetration.

Well here is mine at deck level. I used Sikaflex to seal it but next time it would definitely be Butyl.

[Cyrus Safdari]

Stainless steel should not be sealed in anything, even 316 will corrode if deprived of access to air. This is why ss chaiplates have to be fully removed for proper inspection of the sealed side. Pit or crevice corrosion happens on its own, doesn't need to even get wet.
That extra tab will be great for crevice corrosion where it is welded on
The idea of chainplats is to distribute the load so if you want to improve on it make the longer and-or wider
Or use bronze $$$

[Drinky Crow]

Originally Posted by Cyrus Safdari

That extra tab will be great for crevice corrosion where it is welded on
The idea of chainplats is to distribute the load so if you want to improve on it make the longer and-or wider

Using 316L obviates crevice corrosion at weld boundary.
Bulkhead not tabbed to deck/cabin, c/p horizontals needed for "structure".
As per navel architect.

https://www.youtube.com/watch?v=F5EU...nel=SailingXTC

[Cyrus Safdari]

Originally Posted by Drinky Crow

Using 316L obviates crevice corrosion at weld boundary.

I sincerely doubt this
https://www.offshore-mag.com/busines...s-steel-tubing

[Drinky Crow]

I don't see 316L mentioned in that article.
The welds are above deck anyways so inspection of them is easily facilitated. Chainplates are 3/8", horizontals 3/16". I ain't worrying.

[Ballsnall]

Originally Posted by Cyrus Safdari

Pit or crevice corrosion happens on its own, doesn't need to even get wet.

To my knowledge you need moisture for crevice corrosion to occur and as the oxygen in the moisture is used up then crevice corrosion occurs and is more severe in an acidic environment. Ie salt water

[/QUOTE]
That extra tab will be great for crevice corrosion where it is welded on
[/QUOTE]

I would agree with this as the irregularities in the weld create crevices for the corrosion to begin. The smoother the weld surface the more resistant it will be. There is also the issue of carbon precipitation of the stainless which could lead to cracks forming depending on the stresses.

I would have to assume these issues were considered in the actual design and the fact that the original has performed adequately of many years.