Fasteners

I have been told by multiple realiable sources that stainless steel fasteners don't belong below the waterline where they will be completely submerged all the time. The rational behind that statement is always that stainless steel requires an oxygen environment to maintain its high resistance to corrosion. I have found no evidence that this is true and was actually quite surprised to hear this because I am a structural engineer and specify stainless in many applications. Anyway, I am about to purchase two-thousand silicon-bronze fasteners to begin refastening my 1964 37-foot Egg Harbor with and just thought it would be a good idea to do one final search for information. So if anyone out there knows about the do's and don'ts of stainless steel please let me know, I may be doing a lot of work for nothing. Thank you.

[gonzo]

The problem with stainless steel below the waterline is crevice corrosion. The layer of oxide in the surface keeps oxigen from reacting with the rest of the metal. Below the waterline, electrolisis removes metal at the contact point between the head of the fastener and the surface. The screws look from the outside , but when removed show a "necked down" right under the head. Also, with microcoscopic examination, they show tiny cracks and tunnels where the iron from the alloy was removed electrolitically. Another contributor to the corrosion problems is that fasteners are usually 304 stainless, which is a rather low grade.