Mounting aluminium nav lights on stainless steel pulpit

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geoffcollins

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Hello

I've just bought some lopolights. I plan to mount them on the pulpit, but wonder if there is any issue with bolting aluminium to stainless steel? I must confess to not understanding anything about metals reacting with each other, thus the question.

Cheers

Geoff
 
Ali and stainless are quite far apart on the galvanic table thus liable to electrolytic corrosion. Insulate the two metals if possible as pulpits regularly get dosed with electrolite (seawater).
 
I'm not familiar with the construction of the Lopolights but I am assuming from your post that they are aluminium (I wonder why not plastic).

Insulation of all stainless steel from aluminium is one route you could take but that would involve bushing the stainless bolt where it passes though the aluminium.
I think effective insulation with Sikaflex may be difficult to achieve.

I suggest you use barium chromate paste (Duralac)

Not necessary for the stainless/aluminium to be doused in seawater for then to become solidly corroded together. I just renewed my tricolour. To the best of my knowledge it has never been doused in seawater but the stainless bolts through the aluminium bracket were very reluctant to be separated from it!
 
Would a bed of sikaflex do the job or would the bolt connecting the two be an issue?

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No the bead woud not do! and if it did then the bolt would prevent it. Can you use a clamp fitting and wrap insulating tape around the pulpit under the clamp?
 
[ QUOTE ]
I'm not familiar with the construction of the Lopolights but I am assuming from your post that they are aluminium (I wonder why not plastic).
I suggest you use barium chromate paste (Duralac)


[/ QUOTE ]

So with this paste - I could just cover the bolts in it and daub some in the holes and all would be good?

Sorry for my ignorance /forums/images/graemlins/smile.gif

Geoff
 
i have this all the time with an aluminium boat and attaching s/s to it. The best two things you can do are to use Duralac - zinc chromate paste, but put the Duralac on and wait for it to dry before bolting/attaching. In addition if you can get some Nitrile sheet and make a gasket this will help reduce the risk of corrosion which at the end of the day mostly just welds alu and s/s together. Try www.martins-rubber.co.uk for Nitrile.
 
[ QUOTE ]
i have this all the time with an aluminium boat and attaching s/s to it. The best two things you can do are to use Duralac - zinc chromate paste, but put the Duralac on and wait for it to dry before bolting/attaching. In addition if you can get some Nitrile sheet and make a gasket this will help reduce the risk of corrosion which at the end of the day mostly just welds alu and s/s together. Try www.martins-rubber.co.uk for Nitrile.

[/ QUOTE ]

Thank you - this is very informative.

Cheers

Geoff
 
You could always place a rubber gasket beween the pulpit rail and the light and drill the holes in the rail so that a plastic rawlplug could fit over the bolts then you will also comply with the Lopolight instruction that the light should not be earthed.

I am a bit puzzled why earthing the case is a problem.. Note the instructions for filling the terminal spaces with sikaflex to keep the water out!!
 
I recently had a similar problem with the stainless bolts holding my hard vang to my boom falling out. I used rivet nuts (aluminium) to protect the boom. The only thing that will deteriorate now are the rivet nuts, and it is an easy job to replace them every couple of years I will replace them, job done.
 
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