Rudder Corrosion

[Don from Peconic Bay]

I'm about to start my foiled rudder project and have found so many great ideas posted here by those talented folks who have shared their rudder projects.  Before I start I am curious to know what others did to prepare the original aluminum rudder plate before covering it with foam. Mine is quite corroded. Pressure washing has removed a lot of the corrosion but can't get it all. Is there a product for aluminum that will convert the remaining corrosion similar to rust stop for iron.  Or should I just coat with a primer before applying foam.  Thanks for any tips you can offer.
Don

[Floridagent]

Aluminum oxide is purported to protect aluminum.  So, I would wonder if it needs to be removed.  As I recall there are discussions on the forum as to what may be members' best experiences painting aluminum. Obviously, the primer needs to work well with aluminum oxide as well as aluminum itself.  Good luck with your project!

[Bob23]

I sanded, sanded and sanded some more and used a zinc chromate primer. Worked well and has held up. The exposed part of the blade I then painted with Rustoleum bronze spray paint and it too has held up well. I sail in a salt water area.

[Don from Peconic Bay]

Thanks Bob, sounds like a plan.  I printed up my templates today and as soon as the garage warms up a little I'll get to work .
Don

[Bob23]

Welcome. I took a different route with my rudder. It's a wood sheathed foil build around the original aluminum blade. The procedure is buried deep in the archives of my thread here under the 23 section "The continuing adventures of Koinonia" but the photos have probably disappeared due to that dreaded Photobucket policy change. I can email you a few if you'd like. They may be helpful even if you're not going to build yours as I did. It's holding up well considering it's now 7 or 8 years old. It really enhanced the boat's performance and looks great with a clear finish over the wood which resembles Mahogany.

[Don from Peconic Bay]

Bob,your rudder refit was way beyond anything I could handle and it looked great.  Glad to hear that it has held up well and the performance improvement.  Not sure if I'll go with the hardwood leading edge or just foam the whole thing and give the leading edge an extra layer or two of glass. 

[Bob23]

Don, sorry I'd forgotten that we'd talked about this already. The senior moments are starting to last weeks!! Happy rudder new year to you!!

[MacGyver]

Not sure if you started but I would highly suggest sanding that rudder down with heavy grit paper like 60, down to 36, to get a good bite into the aluminum.
On the corrosion, it is not a good thing to leave on there, but if you could use a wire brush disc to get into divets and such would be preferable, then on parts you cannot remove I would coat in straight epoxy first, then sand that and bite into it with a leveling compound mixed with epoxy, if using West System I recommend 404.

Then build off of that.

Mac

[Don from Peconic Bay]

mac
Should I use zinc chromate primer before I epoxy it or just epoxy over the bare aluminum. 
Thanks,
Don

[MacGyver]

Epoxy over the bare aluminum, reasoning is that a heavy scratch will help that bond out immensely whereas if you went with a zinc chromate primer you are adding another possibly layer of de-bonding.

I did it on my rudder and let me tell you, no issues so far with any of it.

Also when I worked on boats all those years, this was common practice for me and never had a return. Side note, I did the same with LEAD, and cast iron as well with similar outstanding results. Keep in mind we only used West System at the shop so product usage in my opinion was key as well.

Mac