Should stainless steel inside a rudder be coated for corrosion inhibiting?

[Jon Hacking]

Originally Posted by Wind River

...There are parts of the stainless stock that have corroded badly and I am replacing all of these components. Most of this stainless steel is encapsulated in the fiberglass. Is it recommended to prime or coat the stainless before glassing it into the rudder?...

We ended up with a SS rudder as well, as the old one corroded enough it broke off. We glassed in the SS, which isn't ideal (as has been pointed out) but it's worked well for the last 5 years.

Epoxying SS is not trivial. You must scratch it with sandpaper & clean it up well to remove any oils. Paint on the epoxy resin, & then IMMEDIATELY SAND through the wet epoxy with wet/dry, about 80 grit. This will sand off the oxide layer that has formed on the SS (as well as providing additional key). With no free oxygen around, the SS can't oxidize, & the epoxy will then bond with it. This will provide good chemical adhesion as well as mechanical adhesion. It will also break down the surface tension, so the epoxy flows out smoothly & evenly.

Once the rudder has been completely sanded, but before the epoxy has started hardening, you can put on your fiberglass layers. You want to lay it up wet-on-wet, for best adhesion. We put on 2 layers of glass, then some fairing compound (our SS wasn't quite the right shape) & then a final 2 layers of glass. But we're a cat with spade rudders. It looks like your rudder should only need a couple layers of glass before priming & antifouling.

[moseriw]

YES! Stainless V4A is absolutely NOT corrosion free! That is why almost all metal parts must be connected to the sacrifying anode.

[robintrevors]

Originally Posted by Emmalina

Stainless requires oxygen to remain stainless ! Having said that its better than most things. I would just clean it up and glass on top. Thats what I did with my rudder and used 304 on parts below the water line !

Try ospho straight on the SS and leave it over 24 hrs it will react with any rust that is within the welds etc. Then use epoxy etc 5200.make sure you have a great seal. Hudson 50 is a Taiwan build, generally their SS is not good quality. Look at the chain plates etc

Best Robin

[Boatguy30]

A friend of mine reused all the old, pitted stainless on a new rudder after a bad grounding on his Formosa 50. I was appalled. Fortunately, he never really finished the rigging so after about 6 years he's only motorsailed in light winds over to the Bahamas!

[GordMay]

Greetings and welcome aboard the CF, Robin.

[sv.antea]

in 1981, my yankee 30 skeg mounted rudder was shot. Bronze shaft with bronze fingers peened in, the fingers/rods started to wiggle in their holes and the rudder was swinging a degree or two on the stock. So I built a new rudder using 316 stock, epoxy glass over high density foam and 316 flat bars welded to the stock. There is a heel bearing, so the shaft leaves the rudder in two places.
To minimize the chance of water getting inside the rudder, I "wet sanded", meaning using coarse wet/dry sandpaper dabbed in epoxy I scrubbed two or three inches of the shaft where it exits the rudder. Then, before the epoxy coating kicked I tightly wound fiberglass string around the shaft, hoping the tension of the string would help sealing the rudder. Later of course, the skin of the rudder was carefully glassed to the so formed sleeve. I had no idea how much the process would help, but figured it couldn't hurt. My tests shown this epoxy wet sanding to be best of recommended methods to encourage epoxy adhesion to metal. Did not work on bronze, but worked very well on keel lead.
I have no way to tell what the shaft looks under that epoxy sleeve now, but last haul out, the rudder sounded like it was not water logged. That's 38 years later. Next haul out I can check more scientifically like: The rudder was originally carefully balanced with a bit of lead in the trailing edge so that when held by the stock horizontally just under water, it displayed neutral buoyancy moment. (To get no false helm when heeled.)
Just an anecdotal evidence in support of above method.

[Wind River]

The "wet sanding" with epoxy sounds like a promising way to get good adhesion to the stainless. I am skinning the hull in vinyl ester and was going to do the same with the rudder. Maybe I will do just the rudder in epoxy to give it the best chance of keeping the water out and in turn giving the stainless the best chance at lasting another 37 years.

I did plan to passivate the welds and maybe the entire stock for a little added security against corrosion. The heaviest corrosion on the old stock was right at the welds. Leaving it exposed to oxygen/seawater is not really an option as there will always be a surface against the rudder that will be potentially starved of oxygen and may possibly get wet. I'm hoping sealing it up the best I can will be good enough. As has been pointed out, this may not be ideal, but should be good enough.

Thanks for all the input.