Boat Forum / Building / July 2008

Pete,
Your aluminium mooring cleats will be anodised, hope so anyway. This helps
resist corrosion. Where stainless steel fasteners or other parts are in
contact with aluminium parts the joints should be smeared with a zinc
chromate corrosion inhibiting paste such as Duralac. This is a bright yellow
paste, you can buy a tube from a chandler or from the internet for about
£10. If stainless steel fasteners fitted into aluminium are exposed to salt
water you will get corrosion of the aluminium to white corrosion product,
the inhibiting paste certainly helps to reduce this.

Allthough this combination of materials is not ideal, it is the best
practical solution for much hardware on sailing boats, obviously there are a
great many aluminium masts with stainless steel fittings attached and they
last a long time.

As for aluminium wood screws, they do exist, as you can tell from an
internet search, but as far as I am aware they are not something you can buy
from high street shops.

John

Pete,
The only serious issue with stainless in salt water is crevis corrosion and
as this is not under water, that problem is not severe. However the big risk
is electrolytic corrosion because of the dissililar metals. The solution is
to prevent moisture from migrating along the thread and becoming an
electrolite. To prevent that and allow easy extraction use an anti-sieze
compond found in auto supply stores. When using stainless wood screws to
fasten the fairleads, use a bedding compound around the screws and under the
base.
Steve

Thanks guys, i know what to do now
Pete