Rusting Chain Plates

[kjames]

I've done a search and could not find what I wanted.


I have a ‘new to me’ steel yacht. Has painted (I presume) steel chain plates. Some rusting fairly a bit. Rigging is stainless so I guess steel vs stainless issue is at play. Apart from cleaning up and painting with quality paint system, is there anything else that can be done to limit rust at these locations? Cheers

[Amgine]

Not an expert with either steel or stainless, but remember to consider rig grounding.

[Kapena]

You may only have a rust problem but...just for you to think about.
Chain plates have a life limit, just like the rest of the standing rigging. It's metal fatigue. My rigging lasts only 5 years but most goes for 10 years, depending on a lot of factors. Even at anchor your rigging "pumps" from the rocking motion.
Do you know when they were last replaced? Perhaps get a rigger to inspect it and all your rigging. I know what to look for, inspect every morning at the deck and several times a year up the mast, but I always pay to get an independent eyeball on this once a year. You can replace the rigging yourself and have new chain plates made at most machine shops. Just something to think about.

[seandepagnier]

If the boat is steel why do you even need chainplates?

Maybe you can just drill some holes in the rail where it isnt rusted too bad and put your turnbuckles through them.

[DeepFrz]

You would probably get some more informed answers at "The Metal Boat Society" forum.

[FSMike]

I was going to ask if you had chainplates are they bolted through the hull or welded on?

[kjames]

From the responses I think I should not have used the term chain plate. In effect they are just a piece of steel plate welded to the deck.

For your info, what got me thinking about the subject was a post on the Roberts forum regarding "Nylon Shoulder Bushes - Machine Screw Insulators" ( Nylon Shoulder Bushes - Machine Screw Insulators). These separate say, SS bolts from a steel media. So I just wondered about a more elaborate version for rig / deck connections. Cheers

[DeepFrz]

You shouldn't have to worry about stainless steel to mild steel connection. They are quite close on the galvanic scale. What you have is the working of the turnbuckle wearing off the primer from the mild steel exposing it to the elements, a sure recipe for rust. You might want to try welding a piece of stainless to your deck connection (chain plate for lack of a better word). I don't know if that is possible or not on your boat without going to a lot of effort.

[stillbuilding]

Originally Posted by DeepFrz

You shouldn't have to worry about stainless steel to mild steel connection. They are quite close on the galvanic scale. What you have is the working of the turnbuckle wearing off the primer from the mild steel exposing it to the elements, a sure recipe for rust. You might want to try welding a piece of stainless to your deck connection (chain plate for lack of a better word). I don't know if that is possible or not on your boat without going to a lot of effort.

I reckon DeepFrz has it. If your S/S chainplate flat bar is welded directly to the mild steel deck I would look at knocking up a S/S pad to fit over the chain plate and weld to the plate and to the deck so is all one piece. Maybe reasonable to use a bushing to prevent wear of the plate. If you can get a pic of the issue it would be easier to assess and offer advice.

[kjames]

Thanks guys. Welded SS plate sounds worth a thought - considering metal fatigue (after 28 years of service) that might be a sensible move. Have to check deck integrity as well but it is 4mm thick steel which is more than some steelies.
Here's the best photo I have of it - just cropped out from another. You can just see rust 'leaking' out around plate.

Cheers

[stillbuilding]

I would take off the turnbuckle, clean up the steel and examine more closely. That pic looks as though the rust is coming from the turbuckle/chainplate interraction rather than anything to do with the deck. S/S will rust and if that is the case here you may have to clean it up, add a bushing and repaint. Could be pretty simple job with just bit to time.

[bangkaboat]

Originally Posted by stillbuilding

I would take off the turnbuckle, clean up the steel and examine more closely. That pic looks as though the rust is coming from the turbuckle/chainplate interraction rather than anything to do with the deck. S/S will rust and if that is the case here you may have to clean it up, add a bushing and repaint. Could be pretty simple job with just bit to time.

+1
once you've removed the paint/primer you can determine extent & reason for issue. If you're still not sure, snap a picture at that point & post it. As you're probably aware, some folk use galv. wire rigging to avoid these types of issues. But this is a repair job, nothing catastrophic.

[bangkaboat]

If you have the skills or know someone who does, I'd suggest fabricating ss plates, if you don't want to have this as aregular maintenance & repair job. otherwise, if much of the steel is eaten, you can build it back up. You could run a ss bead(weld) around all contact surfaces to reduce issue as well, including filling any resulting pitting.

[Boracay]

+2 for remove, check and repaint.

The main worries are that enough steel has rusted away so that there is insufficient strength and that the rust has restricted oxygen to the turnbuckle and it has started to corrode.

I'd take it apart after properly supporting the rig, clean it up with a wire brush, sandpaper, phosphoric acid, Dremel and then follow with the usual procedure you use for touch up.

I'd also be tempted to replace the turnbuckle.