stainless or silicon bronze

[freddyray21]

There seems to be some debate on another forum I frequent about the type of fasteners to use below the waterline. I had intended to use stainless on my boat I am building, but I am told due to crevice corrosion that silicon bronze is the way to go. However, in everything I am reading it appears that salt water is the culprit in crevice corrosion. I am 500 miles from salt water and to be honest this boat is so small I don't think there is a body of salt water I would put it in. Further the plywood and the screws will be covered with poly and mat. Stainless or silicon bronze?

 

[wire2]

Re: stainless or silicon bronze

Depends on the ss grade. I'd prefer the bronze over 304 stainless, but with 308 or better, it's a moot point.

 

[seven up]

Re: stainless or silicon bronze

Stainless steel requires oxygen. Sealing them up below the waterline will cause crevice corrosion due to the lack of oxygen. Saltwater is not the issue because the stainless is encapsulated.

 

[dingbat]

Re: stainless or silicon bronze

If you encapsulating them in glass it realy wouldn't matter but I would go with 316 stainless as it would be less reactive overall than the silicon bronze.

 

[seven up]

Re: stainless or silicon bronze

I guess you want to hear it'll be ok.

 

[freddyray21]

Re: stainless or silicon bronze

okay for what? do you have an opinion? The thumbs down seems to be for neither since and either or question cannot have a yes or no as an answer unless either are okay or neither are.

 

[tommays]

Re: stainless or silicon bronze

I work with all metals in NON-BOAT machine building

With mostly 304 and 316

"Crevice corrosion occurs in stainless steel and other metals when the metal is covered, but immersed in a corrosive liquid such as seawater. Normally, stainless steel forms a protective oxide coating that protects it. In a small wet crevice, however, the oxygen becomes depleted and cannot restore this coating. As the affected area grows, chlorine ions (from the salt in the water), migrate into the crevice and build up a concentration. The chlorine ions make the solution acidic and corrosive, attacking the protective coating and the metal underneath."

Everything can react with something Get a bit of Bronze and ALU and watch the party


Put the wrong never-siez on a 316 SS bolt and put in and ALU PLATE dont ever expect it come out again if it gets wet


The biggest problem with SS would be getting REAL SS as with all the offshore hardware everything has become supect




So i would say unless you doing through-hull fittings it is a non-issue as it seems to need to be immersed in saltwater to happen






Tommays

 

[dingbat]

Re: stainless or silicon bronze

The biggest problem with SS would be getting REAL SS as with all the offshore hardware everything has become supect Tommays

Problem solved. How many do you want to buy?

http://www.thermo.com/com/cda/product/detail/0,1055,10122008,00.html

 

[freddyray21]

Re: stainless or silicon bronze

I think to be on the safe side from all I have heard I will go with the silicon bronze to attach the plywood to the frame below the waterline. It will cost me twice as much in the beginning, but save me money later if I don't have to replace it.

 

[seven up]

Re: stainless or silicon bronze

What type of boat are you building FR ? Skiff, Dinghy, Single Sheet ? Clinker hull ? Any pictures ?

 

[freddyray21]

Re: stainless or silicon bronze

it's an ACE a two cockpit runabout from the 50's

 

[seven up]

Re: stainless or silicon bronze

The SANDE ACE. Wild !


Enjoy

 

[pgdignan]

Re: stainless or silicon bronze

As a recovering sailboat owner I've had way more experience (mostly bad) with every kind of metal known to mankind. 304 stainless would be fine for fresh water, it's the kind of stuff cheap handtools are made of and other lower end stainless stuff (that isn't really stainless). 316 stainless shouldn't really give you any trouble regardless of where you install it. Crevice corrosion on 316 was measured by practical sailor magazine a few years back by wrapping a rubber band around a series of bolts and submerging them in salt water for more than a year. Metal loss was minimal. Nicopress stainless, if you can find it is absolutely remarkable in its ability to resist almost all corrosion but I don't know if they use it in fasteners. As for bronze it predates just about every other metal in use and I've seen bronze fittings on derelict and sunken boats that were almost as solid as the day they were made. Bronze or good quality stainless will certainly hold your project together.

 

[Mark42]

Re: stainless or silicon bronze

All the wood boat kits I looked at came with silicon bronze fasteners. Not one offered stainless (except for the deck hardware - cleats, etc).