Rust Under Swim Platform

Serenity

I own a 2005 320 and can not stop the hardware under the swim platform from bleeding rust. I have replaced all the stainless with nuts, bolts and washers bought from West Marine three years ago. I am also in the northeast so the boat is out of the water 5 months of the year. Anyone have any suggestions on how to stop this. I clean the rust stains off prior to launching and when it comes out of the water in the Fall--it is back. Thank you for your suggestions.

dropout

Does the rust have anything to do with acid washing the bottom? Im in the Great Lakes and I notice that after the acid wash the stainless steel hardware under the platform gets a little pitted with rust, but a quick cleaning its gone.

Black_Diamond

If you use a steel wire brush to clean your stainless you are the problem.  It leaves behind iron..that then rusts.  Stainless hardware works by 'resealing' itself with a chromium oxide.  You can remove the iron by treating the stainless with a bronze wire brush, then passivating it with a nitric acid solution (usually ~5-10% acid in alcohol..google it).  

Serenity

No I never acid washed the hull--only soap and water when it comes out of the water. I see even other manufacturers have the same issue. You know I do not see it when the boat is in the water because the swim platform is so close to the water but it is the idea of it. One of those pet peeves.

Black_Diamond

You could just bottom paint them too.

Serenity

I do bottom paint the supports up to the waterline but it is the underside of the swim platform that looks really bad.

Black_Diamond

Here is a great read. It goes back to my earlier post about iron/steel contamination. Wire brush, wrenches, sockets... Passivate it!

http://sperkoengineering.com/html/Rust.pdf