Mixing stainless and aluminium

[jeanette]

I am replacing the stanchion bases and attaching them to the aluminium toerail (through to wood) using stainless steel screws.

Can anyone tell me what nature of gunk I should fill the hole with before I re-attach?
The old screws came out very quickly after 5 years and an Atlantic crossing, as the previous owner had done a good job. But I don't know what he used.

Any ideas?

 

[Guest]

Re: Mixining stainless and aluminium

Essentially the anodizing should insulate the screw from the alloy however belt and braces always work better. If using counter sunk screws I would be temped to go for polyurathane bedding compound, set the screws down but not too tight so as not to squeeze out all bedding and clean up. then when dry finally tighted. This leaves a good layer of bedding under the screw head. Iv'e used it sucessfully on alloy cleats but not toe rails. Alternativly and much easier if using roundhead just put nylon washers under the heads, preferably the ones with a small lip that locats into the hole. If doing this I would still add a drop of sealant to the thred to help stop water penitration into the wood. Anthing that electically insulates the screw from the toe rail will work.

The other piont is why not use bronze screws which are nearer to alloy in galvanic series and don't suffer the problems of s/s which when buried in wood can corrode due to lack of oxigen.

Roly, Voya Con Dios, Glasson, Lancaster

 

[30boat]

Re: Mixining stainless and aluminium

Stick to stainless steel screws.The copper in bronze screws will quickly attack aluminium through electrolisis .

 

[Guest]

Zinc chromate paste is recommended to protect screw thread interfaces but has been known to leach out when continually exposed to sea water. Sikaflex does an effective job here. If flatsurfaces are clamped/bolted together, Blue Peter's ubiquitous sticky backed plastic does a good job of keeping the two materials apart

 

[jeanette]

Thankyou for the advice. I'll get started this week-end.

J

 

[Guest]

Use Tef-Gel on the threads.
http://www.users.bigpond.com/jim.chambers/Tef_gel.htm

Alan