Silicon Bronze vs Stainless

[rblevens]

If I can get stainless fasteners locally cheaper than mail order silicon bronze- is the stainless ok?

[rleete]

Stainless steel fasteners are subject to "crevice corrosion". That is, when isolated from oxygen (as they would be when encapsulated), they corrode away. If not encapsulated, they just plain rust (even 316 rusts over time). Crevice corrosion results in the threads rotting away, and the joint fails. Rust causes staining and discolors the wood.

Fasteners, as expensive as they seem, are a tiny portion of the cost of constructing a boat. Unless it's a cheap rowboat, you are better off spending the money up front and doing it once. Imagine building a 20-something foot barrel back that you spent years working on, only to have the screws make it look like hell before you even use it.

[PeterG]

Ditto what rleete says about stainless not being a good choice. Generally speaking if some part of the stainless is exposed to air there will be a lot less crevice corrosion. The stainless forms a thin oxide layer that protects it from further corrosion. But most boat builds don't have their fasteners exposed like that. Galvanized steel screws are a good in that they are strong and don't suffer crevice corrosion like stainless can. But they will rust if wetted, leaving black stains in the surrounding wood that will look pretty unsightly in varnished areas. I also agree the bigger issue here is why risk it for a relatively small savings compared to silicon bronze screws? That's why most builders here use silicon bronze. By the way, Glen-L has great prices for their silicon bronze screws and fasteners.

[rblevens]

Thanks- now I know!

[Tony Hain]

So I suppose the same applies for bolts etc when attaching prop strut and rudder port. Both of these are bronze (not totally sure as to what alloy) and I have a choice of through bolting these with backing plates using silicone bronze or stainless. As well as the corrosion of the stainless, would you also have to worry about electrolysis between different metals, but would this also apply to silicon bronze as it is not the same metal as my prop strut and rudder port.
I guess the only reson I am asking is stainless is a lot stronger than silicon bronze and there is a lot of strain on a prop strut

[Bill Edmundson]

I used stainless bolts. The bronze and stainless are not far apart on the galvanic table.

Bill