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Old 23-11-2017, 15:58   #1
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Post bronze vs 316L Stainless chainplates

I'm doing a refit on a 1979 model Cheoy Lee. I'm renewing the standing rig
and just want some inputs on whether or not I should renew the old bronze chain plates for new 316L Stainless chain plates. Actually I'm just guessing that the chain plates are made from bronze since it looks like bronze. If anyone knows other metal is more common please tell me what you think it can be or how to find out what it actually is (preferably without analyzing samples in lab).
From what I can see bronze and ss seems about the same strength, so I should be able to keep the same dimensions I guess?
I just recently learned that ss is prone to rust when there are not enough air available, like inside chalking. Could ss be a less good material since the chain plates are chalked where they pass through the deck?
Do people actually replace chain plates on a schedule? I remember reading something like it should be replaced every 10 years or so.

Thanks for a great forum, I read a lot of the threads and enjoy learning new things.
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Old 23-11-2017, 16:04   #2
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Re: bronze vs 316L Stainless chainplates

If the bronze is high quality I'd probably stay with them. Stainless is cheap and that's why it's used but it is very susceptible to crevice corrosion. Good quality bronze is almost impervious to sea water and often can last the life of a boat but it has to be high quality.
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Old 23-11-2017, 16:18   #3
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Re: bronze vs 316L Stainless chainplates

x2 what Robert said. The other thing good bronze has over stainless is that it will elongate rather than just break.
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Old 23-11-2017, 18:02   #4
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Re: bronze vs 316L Stainless chainplates

If you have already removed them, Iíd try to get them inspected, Iíd assume by eddy current or X-ray looking for cracks, but I would not substitute bronze for stainless, maybe Titanium, but not stainless.
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Old 23-11-2017, 21:11   #5
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Re: bronze vs 316L Stainless chainplates

Quote:
Originally Posted by strandte View Post
'm renewing the standing rig
and just want some inputs on whether or not I should renew the old bronze chain plates for new 316L Stainless chain plates.
+3 for what Robert said

Keep the bronze chainplates and check them every year. They will last the life of the boat and then some..

316 SS is used because it's white, bright and shiny. It corrodes after 20 years with white fine spider web cracks. You see them once, you won;t mistake them. Accordingly, design life is 10 years.

That being the case, it's OK to put 316 SS turnbuckles (that is, count on changing them in 10 or 20 years) on the bronze chainplates. They're close together on the galvanic table so they won't corrode galvanically.
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Old 24-11-2017, 04:47   #6
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Re: bronze vs 316L Stainless chainplates

Greetings and welcome aboard the CF, strandte.
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Old 24-11-2017, 09:53   #7
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Re: bronze vs 316L Stainless chainplates

I would keep the bronze. I replaced the stainless on my boat with bronze last summer. The stainless was riddled with crevice corrosion. Bronze inspires a lot more confidence.

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Old 24-11-2017, 10:16   #8
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Re: bronze vs 316L Stainless chainplates

Keep the bronze unless you see any defects.
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Old 24-11-2017, 11:06   #9
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Re: bronze vs 316L Stainless chainplates

If it has a pinky colour in parts the bronze is past its service life. (Dezincification)
If you are worried about crevice corrosion go 2205 SS which is pretty much the same price as 316L anyway. It as has twice the 0.2% yield strength and chloride/ stress cracking of 316. So less likely to fatigue. (Close to the deform zone)
Weld/machine with CARE. (2205 rods)
There is a REALY knowledgeable guy on CF on this. Hopefully he will chime in.
Search 2205.
I replaced my old CP's with 2205, 30yr old 316 looked perfect but seeing as they were out and didn't want to pay for xray.
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Old 24-11-2017, 11:53   #10
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Re: bronze vs 316L Stainless chainplates

Why are you thinking you should 'replace' the chain-plates? Is it strictly an 'age' thing? Good bronze plates should out last the boat and maybe even yourself.
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Old 24-11-2017, 12:06   #11
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Re: bronze vs 316L Stainless chainplates

Quote:
Originally Posted by Seymore View Post
... That being the case, it's OK to put 316 SS turnbuckles (that is, count on changing them in 10 or 20 years) on the bronze chainplates. They're close together on the galvanic table so they won't corrode galvanically.
Only if you want them to gall up. If fac, nearly all shinny turnbuckles are either chrome plated bronze or SS with bronze threaded inserts. SS turnbuckles are for lifelines and dinghies, since they will gall if adjusted under load.

Finally, grease the treads with Tefgel or similar and your troubles will be few.
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Old 24-11-2017, 12:23   #12
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Re: bronze vs 316L Stainless chainplates

We have SS plates, and I would opt for bronze.

Our 2006 new ;-) chainplates were already dangerously rotten by 2017.

I would go bronze, all other things different.

Where we are, bronze ones are 5x the price on new SS ones though. Beware.

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Old 24-11-2017, 13:14   #13
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Re: bronze vs 316L Stainless chainplates

After 35 years one stainless chainplate broke normal to pull across a bolt hole. We replaced with 316L in the same dimension. The plates were coated with CRC heavy duty corrosion protectant before being installed. We have used CRC on the lower side of our stainless bow sprint for 15 years now. There is never any sign of rust staining even though it is subject to salt and weather. The CRC allows oxygen to pass but keeps out the salt and moisture. The upper portions of the stainless chainplates were polished till just below the deck bottom surface.

We made sure that the deck core wood was cleared from the chainplate since this retains salt and moisture.

It is surprising to hear that bronze might be as strong as stainless. Perhaps some bronzes are in the range. But are they marine grade bronze? We wouldn't substitute without knowing the tensile strength and anti-corrosion properties.
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Old 24-11-2017, 13:22   #14
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Re: bronze vs 316L Stainless chainplates

If your replacing, call Allied Titanium and at least get a quote, you may be surprised, Ti isnít as expensive as it used to be.
http://www.alliedtitanium.com/
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Old 24-11-2017, 13:33   #15
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Re: bronze vs 316L Stainless chainplates

A few amusing comments about bronze. Life of the boat? Bronze parts have been recovered from the bottom of the Med that date back 4000 years - the stuff is incredibly durable. Dezincification? That is confusing bronze with brass - bronze is very stable, brass not at all. Strength? In the great majority of winches the bases are made of bronze, in part because of their strength. There are many bronze alloys available and they have quite different properties but generally they are very corrosion-resistant and strong. I got rid of my stainless chainplates years ago and replaced them with bronze and never looked back. Wherever I can I use bronze instead of stainless, in part because stainless is prone to crevice corrosion which can cause rig failure without notice. No doubt there are many things to be done on the Cheoy Lee to upgrade it: changing to stainless isn't one of them.

Greg
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