Stainless Foundation and Alloy Footblock Corrosion Risk

[RunAgroundHard]

I have new stainless footblock foundations fabricated to replace teak blocks (the foundation angles the footblock at 45 degrees to the deck). I will remount the original Lewmar dual sheave footblock. The footblock is in good condition, made from an alloy material. The deck is GRP.

Do I need to worry about corrosion between the stainless and alloy? If so what should I use to isolate?

The reason I am asking is that Lewmar winches are supplied with isolation pads when being fitted to a mast mount base, that gets pop riveted to an alloy mast so now I am wondering.

Thanks

 

[rogerthebodger]

All the stainless-steel items I fitted to my mast I insulated the two with some thin HDPE cut from a milk bottle

 

[noelex]

Do I need to worry about corrosion between the stainless and alloy? If so what should I use to isolate?

Yes. This is a relatively large mass of stainless steel compared to the aluminium. I would use a plastic spacer underneath the block in addition to Duralac/Tefgel on all the connecting hardware. You can also try and isolate the stainless hardware from the aluminium with plastic inserts, but this is often more difficult.

Sealant to prevent water from accumulating underneath the aluminium is also important.

 

[RunAgroundHard]

Thanks for the replies. I can buy 1.5mm HDPE sheet for pennies and will use that on the base, plus Tefgel to isolate the stainless fasteners. I'll also use butyl to seal around the bolt holes.