Rusting chainplate nuts?

[steve yates]

Noticed some rust and streaks on the nuts of my chainplates, What would cause this? I assumed these would all be stainless.
Getting the mast down in a couple of weeks and will replace them then, but dont want similar down the line.
I’m thinking if I replace one nut I should replace them all, anything I need to take into account doing this?

 

[Halo]

Looks to me like either the washer is not stainless or there is water ingress into the bolt area above the washer that could be causing crevice corrosion. If there is no oxygen around then stainless will rust.
Perhaps change the bolts and make sure they are nicely bedded in topside

 

[Yngmar]

It's caused by leaky leaks. Stainless doesn't mean rust-free. I'd remove the fittings inside and out to check for hidden corrosion and replace the fasteners (bolt + nut).

When resealing, use something flexible like butyl. Degrease thoroughly before applying.

 

[Neeves]

With no disrespect the pictures indicate a mature yacht - the fittings have lasted well. Changing the nuts and bolts looks wise, even if they had looked good. The nuts look like nyloc nuts - and maybe they were not of the best quality (though it does seem the issue is with the washers)

The bolts look in good nick.

There is stainless and stainless......

Jonathan

 

[steveeasy]

Reluctantly I am going to pull mine and inspect them. Looks like you have two nuts on there. seams a good idea. when you replace the nuts check the threads are good as well as the chainplate!! and im going to buy hopefully good quality nuts. Im going to inspect my forestay and backstay at the same time and a much more detailed inspection of mast fittings. Hate looking for problems but cheaper than a disaster.

Steveeasy

 

[vyv_cox]

Reluctantly I am going to pull mine and inspect them. Looks like you have two nuts on there. seams a good idea. when you replace the nuts check the threads are good as well as the chainplate!! and im going to buy hopefully good quality nuts. Im going to inspect my forestay and backstay at the same time and a much more detailed inspection of mast fittings. Hate looking for problems but cheaper than a disaster.

Steveeasy

And put sealant in before you tighten them down. The streaks on the vertical part of the chainplate is very characteristic of crevice corrosion, although there are other possibilities. Eliminate the crevice, eliminate the corrosion.

 

[steveeasy]

And put sealant in before you tighten them down. The streaks on the vertical part of the chainplate is very characteristic of crevice corrosion, although there are other possibilities. Eliminate the crevice, eliminate the corrosion.

Hi vyv cox,
My post was to the OP was generally saying what I am going to do and suggesting he may do the same. I think your comment is helpful for me too. My chainplates look clean but from what you say, one does not know until you pull them if the age is unknown!!.
Thank You.
Steveeasy