Ross M
10-26-2002, 02:34 AM
Author Topic: Salt Water Boat: S. Bronze or Stainless below Waterline?
Hazen Kent
posted 07-06-1999 09:50 PM
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My runabout will oneday be run primarily in salt water. I have heard Go Stainless and Go Silicon Bronze below the waterline as well as through out...which is it?
goosedoc
posted 07-06-1999 11:04 PM
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I have heard that stainless and some kinds of wood when mixed with salt water causes the wood to pull or shrink away from the screw. don't remember if the wood was oak or something else. Where ever i saw this they recommended using silicone bronze throughout. If all of your bungs are tight and varnished over you shouldn't have a problem. My '57 CC was put together with s.b. screws and they still looked pretty good. No necking at the shank. I'm sure Bob C. would no the best answer living on the SF Bay. G' luck.
Rob Lien
Bob Cleek
posted 07-07-1999 02:15 AM
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Go with silicon bronze or everdur bronze (trade name), NOT stainless. The commercially available stainless screws aren't made for marine applications. Few stainless alloys are suitable for marine use (sorry, can't remember the spec numbers... 316, I think?). The major problem with stainless under water is crevice corrosion. Stainless can just turn to Swiss cheese under water. The price difference is negligible. (Order from Jamestown Distributors in bulk... I've found them the cheapest by far.)
Ed Harrow
posted 07-07-1999 12:51 PM
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I think the stainless is 318. I'm going out on another limb here, but I think most stainless relys on an oxide film for protection, underwater the oxide doesn't form and there is the problem. You also need to consider the galvanic potentials(I think that's the term I want) of all the metals on a boat used in salt water. Somewhere I've seen a nice table on the subject. It might be in Jamestown's catalog or web page, but I think it's in a book that I have. Anyway, you want to pick metals that are close together, not far apart, on the table.
When all else fails: Trust Bob
SEANPEAVEY
posted 07-07-1999 04:07 PM
--------------------------------------------------------------------------------
Bob's right. There is a great book called "Metal Corrosion in Boats" by Nigel Warren that goes into great detail about dezincification of brass, crevice corrosion of stainless steel, electrolysis, etc.
The mechanism that keeps stainless steel stainless, is a protective oxide layer that forms on its surface. Stainless needs to be exposed to Oxygen it in order for that layer to form. A fastener in a wooden boat is continuously having its oxide layer rubbed off by the action of the wood around it. When in air, the necessary Oxygen is taken from the air; when in water, it is taken from the MOVING water. However, when water enters the sealed cavity of a bunged fastener, the stagnant water's reserve of Oxygen is quickly depleted. Since no water movement can occur, thereby replenishing the Oxygen, then no protective oxide layer can reform. This is the beginning of crevice corrosion.
While silicon bronze is resistant to chemical corrosion in salt water, you still must be very careful about possible galvanic corrosion occurring when electrical paths are formed through the wet wood with other metals on board. Again, the above-mentioned book has excellent information on the compatibility of various metals with one another (i.e., which metals are more or less noble).
JIM MALONEY
posted 07-07-1999 09:57 PM
--------------------------------------------------------------------------------
Bronze fasteners of all kinds can be purchased in bulk (100 or more of any one size) plus carriage bolts, etc. from AllStar Fasteners, Elk Grove Village, Ill. (847 640-7827) for approximately 35% less than Jamestown Distributors. Ask for Mark Anderson and tell him Jim Maloney recommended you to them.
Bob Cleek
posted 07-08-1999 03:29 AM
--------------------------------------------------------------------------------
Wow! Thanks for the tip! Made my trip to the forum tonight worthwhile. I've got them on my "must call" list. Great info!
Hazen Kent
posted 07-08-1999 05:53 AM
--------------------------------------------------------------------------------
Jim...tried to e-mail you last night but it didn't work. I too wanted to thank you for the great tip.Take Care. Hazen Kent
Ed Harrow
posted 07-08-1999 10:16 AM
--------------------------------------------------------------------------------
Jamestown 1999 catalog, page 14, has a "compatible metals table" or Galvanic Potential list if you will.
They recommend 316 below the waterline. Looking at the table looks like SS and SB would not be a good combination.
Mercury
Monel
Nickel
Sil Bronze
Copper
Red Brass
Bronze (Aluminum)
Gun metal
Yellow Brass
Phosphor Bronze
tin
Lead
Stainless
iron
mild steel
aluminum
Cadmium
Gal iron and steel
zinc
magnesium
You don't want to use metals "far apart" on the list.
Ed
Steve Faehnle
posted 07-08-1999 01:50 PM
--------------------------------------------------------------------------------
I have found McFeeley's Square Drive Screws to be an excellent supplier as well.
Hazen Kent
posted 07-08-1999 04:47 PM
--------------------------------------------------------------------------------
Wow! Thanks Ed...great stuff! Hazen
Ed Harrow
posted 07-11-1999 11:02 PM
--------------------------------------------------------------------------------
Hazen, You're welcome.
John
.. posted 07-13-1999 08:38 AM
--------------------------------------------------------------------------------
You can use bronze with no problems below waterline, but you must put a piece of zinc close to the bronze. The zinc gets used and the bronze stays OK.
noquiklos
posted 07-14-1999 06:59 AM
--------------------------------------------------------------------------------
Pshaw. I have 2 wooden sailboats, bronze fastened, iron keel, and use no zincs at all. Also, I have no through hulls in one, and 2 in the other, (cockpit scuppers) and no inboard motors. One is 64 years old, the other 38, and the fasteners, (spot checked every haulout) are in like new shape. Zincs protect inboard motors and prop shafts, but as long as there is no more noble metal in contact with the water, you can get away without them, in my admittedly limited experience. Might have something to do with the iron keels, though.
Miller, Robert W.
posted 07-14-1999 10:49 PM
--------------------------------------------------------------------------------
Hazen, why in hell did you start this krap any way? You knew the answer. Don't take up time to walk along a shore all ready past. Ask only what you truley need to know. If you take the time of just one who takes a first step and is cut off, we are all diminished. Bob M.
Ed Harrow
posted 07-15-1999 12:47 PM
--------------------------------------------------------------------------------
"O fan from me the witless chaff of such a writer."
Miller, Robert W.
posted 07-16-1999 11:56 PM
--------------------------------------------------------------------------------
Ed has my number and Hazen has my apoloigy. Now if someone will just limit the Evan Williams, I should not have to stand chastized as often. Still, I would like to see all of you on the quarter deck as the sun sinks below the yard arm. Bob M.
Hazen Kent
posted 07-17-1999 03:09 PM
--------------------------------------------------------------------------------
ah what the heck...no need to stoop.
[This message has been edited by Hazen Kent (edited 07-18-99).]
Hazen Kent
posted 07-17-1999 03:14 PM
--------------------------------------------------------------------------------
...
[This message has been edited by Hazen Kent (edited 07-18-99).]
John Gearing
posted 07-17-1999 06:38 PM
--------------------------------------------------------------------------------
All right all ready!! Let's all strike our colors together, declare peace, and get on with enjoying our boats.
Classic Boatworks - Maine
posted 07-18-1999 02:16 PM
--------------------------------------------------------------------------------
Hazen, your chris was originally fastened with SB for a reason. Stick with it especially in the salt water!
Hazen Kent
posted 07-18-1999 07:41 PM
--------------------------------------------------------------------------------
Thank you...
[This message has been edited by Hazen Kent (edited 07-18-99).]
Hazen Kent
posted 07-06-1999 09:50 PM
--------------------------------------------------------------------------------
My runabout will oneday be run primarily in salt water. I have heard Go Stainless and Go Silicon Bronze below the waterline as well as through out...which is it?
goosedoc
posted 07-06-1999 11:04 PM
--------------------------------------------------------------------------------
I have heard that stainless and some kinds of wood when mixed with salt water causes the wood to pull or shrink away from the screw. don't remember if the wood was oak or something else. Where ever i saw this they recommended using silicone bronze throughout. If all of your bungs are tight and varnished over you shouldn't have a problem. My '57 CC was put together with s.b. screws and they still looked pretty good. No necking at the shank. I'm sure Bob C. would no the best answer living on the SF Bay. G' luck.
Rob Lien
Bob Cleek
posted 07-07-1999 02:15 AM
--------------------------------------------------------------------------------
Go with silicon bronze or everdur bronze (trade name), NOT stainless. The commercially available stainless screws aren't made for marine applications. Few stainless alloys are suitable for marine use (sorry, can't remember the spec numbers... 316, I think?). The major problem with stainless under water is crevice corrosion. Stainless can just turn to Swiss cheese under water. The price difference is negligible. (Order from Jamestown Distributors in bulk... I've found them the cheapest by far.)
Ed Harrow
posted 07-07-1999 12:51 PM
--------------------------------------------------------------------------------
I think the stainless is 318. I'm going out on another limb here, but I think most stainless relys on an oxide film for protection, underwater the oxide doesn't form and there is the problem. You also need to consider the galvanic potentials(I think that's the term I want) of all the metals on a boat used in salt water. Somewhere I've seen a nice table on the subject. It might be in Jamestown's catalog or web page, but I think it's in a book that I have. Anyway, you want to pick metals that are close together, not far apart, on the table.
When all else fails: Trust Bob
SEANPEAVEY
posted 07-07-1999 04:07 PM
--------------------------------------------------------------------------------
Bob's right. There is a great book called "Metal Corrosion in Boats" by Nigel Warren that goes into great detail about dezincification of brass, crevice corrosion of stainless steel, electrolysis, etc.
The mechanism that keeps stainless steel stainless, is a protective oxide layer that forms on its surface. Stainless needs to be exposed to Oxygen it in order for that layer to form. A fastener in a wooden boat is continuously having its oxide layer rubbed off by the action of the wood around it. When in air, the necessary Oxygen is taken from the air; when in water, it is taken from the MOVING water. However, when water enters the sealed cavity of a bunged fastener, the stagnant water's reserve of Oxygen is quickly depleted. Since no water movement can occur, thereby replenishing the Oxygen, then no protective oxide layer can reform. This is the beginning of crevice corrosion.
While silicon bronze is resistant to chemical corrosion in salt water, you still must be very careful about possible galvanic corrosion occurring when electrical paths are formed through the wet wood with other metals on board. Again, the above-mentioned book has excellent information on the compatibility of various metals with one another (i.e., which metals are more or less noble).
JIM MALONEY
posted 07-07-1999 09:57 PM
--------------------------------------------------------------------------------
Bronze fasteners of all kinds can be purchased in bulk (100 or more of any one size) plus carriage bolts, etc. from AllStar Fasteners, Elk Grove Village, Ill. (847 640-7827) for approximately 35% less than Jamestown Distributors. Ask for Mark Anderson and tell him Jim Maloney recommended you to them.
Bob Cleek
posted 07-08-1999 03:29 AM
--------------------------------------------------------------------------------
Wow! Thanks for the tip! Made my trip to the forum tonight worthwhile. I've got them on my "must call" list. Great info!
Hazen Kent
posted 07-08-1999 05:53 AM
--------------------------------------------------------------------------------
Jim...tried to e-mail you last night but it didn't work. I too wanted to thank you for the great tip.Take Care. Hazen Kent
Ed Harrow
posted 07-08-1999 10:16 AM
--------------------------------------------------------------------------------
Jamestown 1999 catalog, page 14, has a "compatible metals table" or Galvanic Potential list if you will.
They recommend 316 below the waterline. Looking at the table looks like SS and SB would not be a good combination.
Mercury
Monel
Nickel
Sil Bronze
Copper
Red Brass
Bronze (Aluminum)
Gun metal
Yellow Brass
Phosphor Bronze
tin
Lead
Stainless
iron
mild steel
aluminum
Cadmium
Gal iron and steel
zinc
magnesium
You don't want to use metals "far apart" on the list.
Ed
Steve Faehnle
posted 07-08-1999 01:50 PM
--------------------------------------------------------------------------------
I have found McFeeley's Square Drive Screws to be an excellent supplier as well.
Hazen Kent
posted 07-08-1999 04:47 PM
--------------------------------------------------------------------------------
Wow! Thanks Ed...great stuff! Hazen
Ed Harrow
posted 07-11-1999 11:02 PM
--------------------------------------------------------------------------------
Hazen, You're welcome.
John
.. posted 07-13-1999 08:38 AM
--------------------------------------------------------------------------------
You can use bronze with no problems below waterline, but you must put a piece of zinc close to the bronze. The zinc gets used and the bronze stays OK.
noquiklos
posted 07-14-1999 06:59 AM
--------------------------------------------------------------------------------
Pshaw. I have 2 wooden sailboats, bronze fastened, iron keel, and use no zincs at all. Also, I have no through hulls in one, and 2 in the other, (cockpit scuppers) and no inboard motors. One is 64 years old, the other 38, and the fasteners, (spot checked every haulout) are in like new shape. Zincs protect inboard motors and prop shafts, but as long as there is no more noble metal in contact with the water, you can get away without them, in my admittedly limited experience. Might have something to do with the iron keels, though.
Miller, Robert W.
posted 07-14-1999 10:49 PM
--------------------------------------------------------------------------------
Hazen, why in hell did you start this krap any way? You knew the answer. Don't take up time to walk along a shore all ready past. Ask only what you truley need to know. If you take the time of just one who takes a first step and is cut off, we are all diminished. Bob M.
Ed Harrow
posted 07-15-1999 12:47 PM
--------------------------------------------------------------------------------
"O fan from me the witless chaff of such a writer."
Miller, Robert W.
posted 07-16-1999 11:56 PM
--------------------------------------------------------------------------------
Ed has my number and Hazen has my apoloigy. Now if someone will just limit the Evan Williams, I should not have to stand chastized as often. Still, I would like to see all of you on the quarter deck as the sun sinks below the yard arm. Bob M.
Hazen Kent
posted 07-17-1999 03:09 PM
--------------------------------------------------------------------------------
ah what the heck...no need to stoop.
[This message has been edited by Hazen Kent (edited 07-18-99).]
Hazen Kent
posted 07-17-1999 03:14 PM
--------------------------------------------------------------------------------
...
[This message has been edited by Hazen Kent (edited 07-18-99).]
John Gearing
posted 07-17-1999 06:38 PM
--------------------------------------------------------------------------------
All right all ready!! Let's all strike our colors together, declare peace, and get on with enjoying our boats.
Classic Boatworks - Maine
posted 07-18-1999 02:16 PM
--------------------------------------------------------------------------------
Hazen, your chris was originally fastened with SB for a reason. Stick with it especially in the salt water!
Hazen Kent
posted 07-18-1999 07:41 PM
--------------------------------------------------------------------------------
Thank you...
[This message has been edited by Hazen Kent (edited 07-18-99).]