Stainless steel screws under epoxy !?

Live dangerously, turn around and time the gusts!

Waters warm, and deep too!

 

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what ta heck!! why ya pissin on me?,,i didnt even say nothin yet!! hehe

 

For what it's worth, some comments based on too many years designing and troubleshooting seawater desal systems:

316 SS is superior in corrosion resistance to 304 under nearly all circumstances, because of its molybdenum content.

None of the austenitic (300 series) SS alloys are very good at resisting corrosion from chlorides, a major component of seawater. That problem is aggravated when the surrounding water becomes oxygen depleted, and is compounded as temperatures rise above 25 C. The precise sequence of events and exact cause of SS corrosion in seawater has been and continues to be debated among chemists and metallurgists, but its existence is well documented. The problem is such that, despite the much higher cost, desal plants have gone to "duplex" SS alloys and even a few veeeeeery pricey proprietary ones.

Andre, I'd go with Monel (nickel copper blends occur naturally in nature; Monel is a specific recipe alloy and a trademark of International Nickel) or bronze fasteners below the waterline. Materials with high copper and/or nickel content resist chloride corrosion much better than the nickel chromium (austenitic SS) alloys.

John, I know there are many good sailboat builders using 316 SS keel bolts. The danger is as Andre (DB) described: the possibility that, since it's a boat, some seawater will permeate eventually, no matter how well sealed. Well designed keel attachments are accessible for tightening the bolts and removal for inspection. 316 SS would be OK so long as you inspect the bolts periodically and replace at the first sign of corrosion. You could use Monel, Inconel, or bronze bolts, but they would be pretty costly.

 

Charlie,

Would stainless steel keel bolts through a cast iron keel gain some cathodic protection from being electrical contact with the iron?

Tokens

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Outta points!

 

Short answer is yes. I'd bond everything and connect to zincs, though, for best galvanic protection. (Don't want the iron keel dissolving and causing a capsize ) That's a separate issue from crevice/chloride corrosion.

In the interest of fairness, I should point out that, while many good boatbuilders use SS keel bolts as I described above, there are a number of marine builders who recommend Monel or bronze and state that SS should never be used. I'll stick with my recommendation that SS keel bolts are OK ... so long as you inspect regularly and replace when corroded.

 

I've had experience with an Australian production boat builder that used SS keel bolts in cast Iron. Of the many hundreds of yachts they have built I have never heard of one having the keel bolts replaced. Ive had many surveyed when reselling and its never been an issue....

Cheers
MBz

 

It's funny to watch you guys bitching about this thread being a pissing match, yet you continue to empty your bladders.

 

Haha, I don't know who gave me the points (for the above post) and wrote this:

Answer: In the right circumstances I'd suggest that urine might indeed inhibit corrossion.

In the dark ages, the myth goes that knights pissed on their scale mail in order to prevent rust.

 

Who's bitching?

 

Seems every proponent of using 316 for all and everything is …

 

Oh, I thought we where discussing the merits of specific applications and situations?

 

:idea:

Obviously.

It's the bitching in between that I focussed on in a single post. You know the type:

"Boohoo, had I known this was a pissing match I would never have responded, so here are my response". It just annoy me that people go "I don't want to discuss this, so here we go," thus trying (rhetorically) to state one's own opinion while at the same time saying that if the other side posts his it's suddenly a pissing match.

Don't worry, I'm not taking any of this seriously, just saying.

 

It does seem that the subject is not fully understood even by the extra spurts?

I think I have developed another phobia!

I have read so much stuff on this one, much of it conflicting.

 

Meanz, wotcha gunna call it, inoxaphobia? why just last week I had to condemn 90 fathoms of 22mm staino anchor chain, damned crevice corrosion, curses upon ye little understood(by me too) phenomephobia. All the best in your recovery from Jeff.

 

Ouch.... that's expensive! Stay with the gal then? What in the welds? You do surveys Jeff?