Rust from Screws of Rubber Fender

[rotorman]

I have an extruded rubber fender around my boat. Is is slided on onto a flange and hold in place by wood screws from the top and bottom.

Originally I was using 316 ss screws. After a few years (and a lot of offshore sailing) the screws started to bleed rust. Especially near the lowest area of the fender where water can accumulate. I assume this is happening because there is no oxigen where the screws enter the rubber.

I replaced the screws on one side with silicon bronze screws. Now there is some bronz powder around the bolt heads but no major (yet). And it does not look very nice.

I am concerned that with the bronze screws it won't be much better than with the stainless ones.

Any suggestions?

Cheers
Geza

[delmarrey]

Normally rub rails cover hull joints and have aluminum rivets in them. Don't know if this is what you have but on a 40'+ boat I'm surprised that it has a rubrail set up. I would think it would have a lap joint with a toerail/caprail.

Need more detail or pictures.

[rotorman]

Hi. This is an Amel. Amels don't have traditional hull to deck joins. There is a fiberglass flange on the side just below the deck level which holds an U shaped heavy duty rubber. The flange can also act as a sacrifical energy absorver in case of an impact from the side.
So the only purpose of the screws is to hold the rubber (and they are not related to a hull to deck join).
I guess my real question is what material should I choose for the screws. Stainless (316) seems to bleed rust but only after a while. Bronze turns green immediately and there is green powder around the screws on the rubber.

[Shanaly]

1 are you sure fixings are not brass? i have some which is powdering - acting as a sacrificial anode (to bronze fittings in this case - but once moist they can electrically link to any other metal including nobler ones like bronze which are linked by the 'moist circuit' ). iac you should try wiring your fixings to your yacht's common ground point (earth) - see Nigel Calder's Electrical and Mechanical 'bible' - which just means earthing with a conductive wire each screw to your engine block or other CGP.
2 yep ss needs lots of flow of oxygen to stay ss !!! but a fix is to use phosphoric acid - just paint on and leave. this turns any rust into a beneficial/benign metal compound after an hour or so - so no more bleeding. if you can get in there to scrub, you can make it shiny again too! hope this helps.