Keel Bolts

[F_McMillan]

I've got an E-Boat which has a cast iron lifting keel. The keel bolts are currently steel, prior to launching I'm planning to replace these, is there any reason why I shouldn't replace them with stainless steel bolts?


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[cameronke]

I replaced my E-Boats keel bolts with stainless two years ago. Haven't noticed any problems. I used plenty of copperslip when reassembling as I replace the neoprene gasket between the keelbox and the keel every season. I would value any input from metalurgists or chemist regarding any concerns.

Happy new year to all

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[VirgoVoyager]

Interestingly, cast iron is much less prone to electrolytic action than other forms of iron (especially steel). This is due to the lack of impurities in it. I would see no problem with using stainless steel bolts in this situation.

Speaking as a chemist

Stuart

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[Mirelle]

Well, you can if you want to!

Austenitic stainless steel eg "316" or "18/8" is about in line with silicon bronze, when in the passive state, so the galvanic potential between it and the cast iron is quite large - but since it is the "less noble" metal that is attacked - in this case the cast iron - and there is an awful lot of cast iron, nothing very exciting is going to happen - as long as the stainless steel remains passive. If it doesn't, it will develop pitting, crevice corrosion, leading to "worm holes" right through it. But there are plenty of production boats about the place with stainless bolts through their cast iron keels.

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[iangrant]

An mechanical engineer said to me NEVER use stainless for keel bolts. The main reason being stainless will rust as quick as you like when deprived of oxygen..
I would use the same material as the old bolts!


Ian

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[PuffTheMagicDragon]

The cast Iron keels on my Centaur have been held by stainless studs since 1976. Cyano only comes out of the water for two or three weeks every early June.
I don't think that you should have problems using passive ANSI31 or higher.
Fair Winds!

<hr width=100% size=1>Wally

 

[PuffTheMagicDragon]

Ooops!

Make that "ANSI 316"
Sorry!

<hr width=100% size=1>Wally

 

[F_McMillan]

Re: Ooops!

Having spoken with marine corrosion expert in our company (QinetiQ) it would appear that there is a problem with anaeobic electrolosis with bog standard stainless, so I guess getting the right grade will solve that one. For now I think I'll replace them with steel bolts, copperslip and regular checks.
Many thanks to all for your thoughts and advice.

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