> Don't some metals deposit
> ions on each other or something or corrode more than another kind. I will
> have screws touching the sheet metal in a salt water brew. Are there any
> rules for compatible and incompatible metals. I have some vague
> reccolection that there is.

> Dave

Hi Dave

A metal that doesn't oxidize easily in seawater is obviously best, like silicon bronze (also used in keel bolts), stainless steel, or copper, brass, or some other "marine alloy". As long as the screws you use are made out of the same material as your sheet metal you shouldn't have a problem and won't need to fit a sacrificial anode or anything nasty like that.

If the screws were made of a different metal to your sheet metal then you WOULD have an electrolysis problem, with one metal oxidising the other according to their respective places in "The Activity Series of Metals" (see any high school chem text).

I would expect stainless steel to be your best bet, Stainless should be available as sheet and screws and be fairly cheap. If you're not mooring your boat, and you rinse it of with the hose after each paddle you won't have anything to worry about.

Have you thought about fitting a skeg instead? I've seen some fins made for water skis and wake boards in the Overton's catalogue (or take a look in your local boat shop), they look like they would make a fairly reasonable looking skeg for a kayak. Just offset it a bit to correct your directional problem.

Paul.