Anode fixing studs

oldbilbo

oldbilbo

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I note these are shown in ASAP Supplies' catalogue and elsewhere as galvanised mild steel with plain nuts - which corrode. Why not stainless bolts with s/s nuts....? Or even galvanised mild steel coach bolts....?
 
Something to do with SS and lack of oxygen. Mild steel is fine, just put a dab of lanoguard on the threads.
 
My stainless steel trim tabs ( which have done 8 x 6 month seasons in salt water) have anodes attached to them by A4 stainless steel hardware. Basically, a nut and bolt on each tab, so the bolt is captive and a stainless steel locknut for holding the anode in place. I've not come across any corrosion at all on these nuts and bolts.
 
I welded stainless studs, A4, to the steel hull of my boat during the build and after 4 full years in sea water in Durban no problem with corrosion at all.
 
The mild steel is protected by the zinc. Peardrop anodes normally have a mild steel strap cast into the zinc, which is also protected. The mild steel versions corrode when the boat is ashore but not underwater.

Seawater contains loads of oxygen down to considerable depths. The threads of stainless steel might suffer crevice corrosion due to their design, crevices being inevitable in threaded components, but the chances are they will last as long as mild steel ones for four times the price. There is even a possibility that the stainless bolts, being more noble than the strap, will lead to premature failure of the anode strap, i.e. falling off.
 
vyv_cox said:
The mild steel is protected by the zinc. Peardrop anodes normally have a mild steel strap cast into the zinc, which is also protected. The mild steel versions corrode when the boat is ashore but not underwater.

Seawater contains loads of oxygen down to considerable depths. The threads of stainless steel might suffer crevice corrosion due to their design, crevices being inevitable in threaded components, but the chances are they will last as long as mild steel ones for four times the price. There is even a possibility that the stainless bolts, being more noble than the strap, will lead to premature failure of the anode strap, i.e. falling off.
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Hmmm. I just knew it had to be something 'techie'. I'm unimpressed by all this unwanted corrosion flying about, so think I'll just use a couple of the nylon bolts I have in the shed..... They won't corrode when I'm not looking! ;)
 
oldbilbo said:
Hmmm. I just knew it had to be something 'techie'. I'm unimpressed by all this unwanted corrosion flying about, so think I'll just use a couple of the nylon bolts I have in the shed..... They won't corrode when I'm not looking! ;)
Click to expand...

That will be ineffective. The bonding to your stern gear uses the fastening studs. You are worrying about nothing. Mild steel studs are used extensively for the reasons Vyv gives. Why do you think the specialist anode suppliers use that material if it is inappropriate?
 
Just changes ours. Mild steel and we had tuffnel top hats made to inser into the hole so that the wood end grain was not exposed.
 
I was 'harvesting' my way through a pile of old PBOs and YMs today, while waiting for some paint to dry, and came across this snippet from PBO March 2011....


anodes.jpg



....'a nasty little galvanic cell', eh?

I think I'll hunt out some suitable mild steel coachbolts from my various boxes of 'handy one day' bits. Failing that, I'll ensure no direct contact between the zinc and any stainless components. I expect to dry out a couple of times each year and inspect critically. Maybe I'll keep the nutty nylon bolts for something else.... ;)
 
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