Rust stain, or worse?

[peaman]

In the attached image, what's likely the deal with the prominent rust-colored stain? And just as importantly, what can I do about it, preferably without tearing up my headliner?

This is on a 1987 32-3. The leg with the rust stain is through-bolted and conveniently placed over a zipper in the headliner, so that's easy enough. But given the angles of the other legs, I will need to detach at least one other foot from the deck in order to remove the tubing guard for full access to the rust-stain area. I can also access the above-headliner area under the port-side foot, but that appears not to be through-bolted. Instead, there is a block of wood(?) under the port-side foot with no sign of fasteners. I tried removing one of the screws on that foot, but several turns didn't show any progress, so it doesn't seem to be a normal screw-into-wood-block condition.

Any guidance of how things are put together here will be welcome. There are no signs of water penetration to the interior in any of the foot locations.

 

[Frank Langer]

Davis FSR fibreglass stain remover works pretty well on that. It's available at marine chandleries or on line, not too expensive. It may take a few applications with a tooth brush or similar.
Most people think that stainless steel is stainless, but it isn't always. I'm not sure what is causing the rust in your picture
Frank

 

[Christian Williams]

I use Barkeeper's Friend. It's common for stanchion bases to rust like that. I spray some on before setting up the wash hose, and usually it comes off without needing a brush. You might need a stainless wire brush if rust is bad.

Such products use oxalic acid, hardware store full of them, any will work.

 

[Kenneth K]

The tubing can be removed from the bases without detaching any of the bases. I've done it twice. It' 3/4" tubing and it's pretty flexible.

I had a leak in that same area and had to replace a few square inches of plywood core below the center base.

 

[Nick J]

When I was going over our boat with the surveyor, he said the rust stain at the bottom of stanchions was a sign of the bedding compound had failed. I didn't think too much of it at the time other than to check for leaks and make sure the core was still solid. I haven't fixed the two that he found during the survey 3 years ago. Has anyone else heard this advise?

 

[Kenneth K]

Has anyone else heard this advise?

Well, that has been my experience recently. A broken seal seems to keep the SS fastener "sitting" in water, surrounded by the damp/wet wood core, which causes more rust than a "dry" fitting does.

Good bedding:

Failed bedding: With drips caught on a rag, below. I never actually saw active drips, but this is what I collected over a few months in 2022.

The problem with that center dorade guard post shown in the OP is that it straddles the raised non-skid surface on 2 sides, leaving a void in the middle. I dealt with the same problem two years ago. https://ericsonyachts.org/ie/threads/cabin-top-core-repair-questions.19966/

And, the completed repair:

 

[Kenneth K]

I can also access the above-headliner area under the port-side foot, but that appears not to be through-bolted. Instead, there is a block of wood(?) under the port-side foot with no sign of fasteners. I tried removing one of the screws on that foot, but several turns didn't show any progress, so it doesn't seem to be a normal screw-into-wood-block condition.

From what I remember, the center and starboard base bolts were accessible from the headliner zippers. The port side is wonky though, and, yeah, the through-bolts are covered by a piece of plywood. I can't remember whether I was able to unscrew that plywood piece, or whether I had to cut it away. I did have to un-staple some of the headliner for access.

 

[G Kiba]

I was told that stainless steel will rust where is can't drain or breath properly. Failed bedding is the likely cause here. Replacing the fasteners might be a good idea if they are rusted badly. I have several stanchions to bed this season.