Sudden Stemhead Chainplate Fitting Rust - Time to Worry?

[jkalucki]

The forestay / stemhead chainplate fitting on my (newish to me) 2004 J/109 has suddenly formed some rust on the stainless steel. A lot of it appears to be in rubbing wear areas on the loop under the upper tang, but there's some down in the hull screw cracks too, and maybe a bit behind the toggle. It's possible it's dripped from above to below into the screw cracks, or maybe more is forming there too, but it's hard to tell. The main tang itself appears 100% solid from the outside. Photos below.

Is it time to panic and call in a rigger to replace? Or is this a case of re-passivating with some stainless steel Wichard Wichinox cleaning paste, and watching for recurrence?

Thanks,
John

[Randyonr3]

true stainless wont rust but thats not to say how it was prepaired.. the plate could have been finished off by grinding smooth and the wheel used was one that had previously been used to grind steel, and the fragments of steel were left on the stainless, same as the holes on the front..
sometimes the steel is ground into the stainless..
cleen it and keep an eye on it ..

I had some stainless welded on a piece awhile back and a wire brush was used to finish it off and the wire brush had previously been used on steel.. yep, it rusted..

[neilpride]

No, this is normal , unless the tang is 10 years or more old dont worry to much, one of the benefits of external chainplates and tangs its easy to take a look for cracks, to me this is just external superficial rust, easy to solve with wichinox or another soft acid cleaner , now the way is made it is kinda weird, one main plate and a sub second short plate welded behind the main one, the sub plate i guess its used for a storm jib or some short of inner forestay? the welding top point its a welcome for rust and stress cracks , no idea the ticknes but some lame welders , riggers instead of use a full ticknes plate they Weld 2 thin plates to make one thicker, hiden the welding line with a shine polish surface but at the pin holes you can see the 2 plates very clear , also a fenomenal trap for wáter and future rust cracks, even in some instances the top plate have 2 washers welded to close the gap for wide togles , if you see some small cracks , disconect the plate and replace it, you can dye test or in doubt replace it, its not a big deal , a new spar with sails winches etc,,, its a big deal..... forestays tangs are subject to hig loads and stress, and i am a rigger. Cheers...

[HappyMdRSailor]

Oh maaaaaan....

John... That looks bad... You don't say where you are, but I'd be happy to take your 109 off your hands so the problem goes away...

All kidding aside, it would concern me like it does you, but I wouldn't be lying awake with worry... Me personally would pull the top 2 fasteners, and see if there's any corrosion/staining past the heads on the threaded portion...

If no, I'd rebed 2 new fasteners of known good 316 quality, and see if there's any staining difference between the two groups...

If staining goes beyond the head into the threads... I'd pull the fitting and take a peek behind the plate...

Just what I'd do... certainly not what everybody would...

What kind of sail inventory are we talking about???

[skipmac]

Stainless can rust and also can suffer from crevice corrosion. For stainless to be stainless the surface must be a layer of chrome oxide formed by a reaction of the chrome used in to make SS alloys and oxygen from the air. If the SS has been welded or ground or the surface physically damaged this will expose iron molecules that will then rust. Welded or worked stainless must be passivated (an acid treating process that removes the free iron) to keep it from rusting.

This leads to crevice corrosion which is just like the name, corrosion in a crevice or some similar small, sealed off area. To keep the protective, no rusting, layer the SS must be exposed to oxygen. Otherwise the protective coating is lost and rust forms. This is why SS screws are never used below the waterline, especially in fastening wooden boats.

In your case, the rust stains below the boltheads on the stemhead fitting could be coming from the inside of the bolts. This is an area where it could easily be wet with little to no fresh water flushing around the bolts so the oxygen will be depleted and corrosion begins.

To be sure you should pull the bolts from the stem and inspect them. If you see any corrosion replace them. In fact, if you pull them go ahead and replace them anyway since the bolts won't be that expensive. Then caulk and bed them well to make sure water doesn't leak into the bolt holes.

True story. Good friend with a Westsail 32 saw some rust stains on his stemhead fitting. Pulled the bolts and they were almost rusted in half. The heads looked perfect, the nuts on the inside looked perfect. The shaft of the bolts was eaten away due to crevice corrosion.

[barnakiel]

Looks very much like normal amount of rust that may form once the metal gets scratched or/and contaminated.

You can remove the fitting and get it electro-polished.

b.

[JPA Cate]

I'm more concerned with the top two bolts. Pull 'em, examine, replace if indicated. If water has got in there where you don't want it, remove and rebed the whole fitting. As suggested above, replacing a rig is a big expensive deal.

If you commit to keeping an eye on it. Scrub off the rust with Zud (in the US), rinse well. Then see what happens. IME, screws or bolts that consistently develop a rust stain around them need to be pulled and re-sealed. Also, have had the same kind of bolt failure that was described above for the Westsail. It does happen, the dreaded crevice corrosion, also called oxygen deprivation corrosion.

A.

[jkalucki]

Thanks all.

I think I'm going to use some Whichard Wichinox passivating and cleaning paste and keep a close eye on what happens over the next month. It's odd that I went from zero rust over the last 18 months to this, plus rust on a number of lifeline fittings and rings, all at once. I'm starting to wonder that maybe it was contamination.

Very easy to keep an eye on this, as I dock bow in, so it's right in my face every week. All of the fittings are very probably 11 years old, so everything's right on the edge.

Thanks again.

[Cheechako]

I would just make a habit of cleaning surface rust off anything. SS rusts.. it has iron in it. Some more than others. That piece looks like it was highly polished which helps slow down the corrosion process.
If relatively easy to remove, check the bolts. If you remove the fitting have it hand polished. It's a finer finish that the Matte finish result of passivation.

[skipmac]

From the photos this could be just a little surface rust from age that a little polish would fix or could be something more serious.

If the bolts are really a pain to remove I might try the polish and see if you get rust around the bolt heads returning very quickly. If so I would think harder about pulling at least one bolt to check.

[skipmac]

Originally Posted by Cheechako

I would just make a habit of cleaning surface rust off anything. SS rusts.. it has iron in it. Some more than others. That piece looks like it was highly polished which helps slow down the corrosion process.
If relatively easy to remove, check the bolts. If you remove the fitting have it hand polished. It's a finer finish that the Matte finish result of passivation.

Hi Cheechako,

I have read recommendations on polishing and/or passivating SS but one thing that wasn't clear to me. If you polish the SS does that also remove the free iron on the surface like passivation?

I buffed out a couple of my station bases with a Dremel, buffing wheel and very fine jeweler's rouge. Looks great so far but have not yet soaked it in salt water for the real test.

[Cheechako]

Originally Posted by skipmac

Hi Cheechako,

I have read recommendations on polishing and/or passivating SS but one thing that wasn't clear to me. If you polish the SS does that also remove the free iron on the surface like passivation?

I buffed out a couple of my station bases with a Dremel, buffing wheel and very fine jeweler's rouge. Looks great so far but have not yet soaked it in salt water for the real test.

I believe it does. Passivation is great, but it needs to be very controlled...too much and it attacks the grain boundaries... which results in accelerated rusting afterward. The finer the finish the less exposed the grain boundaries are. I think manual polishing is the only way to get the finest finish.

[skipmac]

Originally Posted by Cheechako

I believe it does. Passivation is great, but it needs to be very controlled...too much and it attacks the grain boundaries... which results in accelerated rusting afterward. The finer the finish the less exposed the grain boundaries are. I think manual polishing is the only way to get the finest finish.

Thanks. Guess I'll break out the big buffing wheel for my bench grinder before I install the new chainplates.

[JPA Cate]

Hey, guys, stop me if I'm wrong, but I thought the best polishing for Stainless is electro-polishing, done at time of manufacture of the object. And that, after that, the Wichard passivating polish was the best. Has this situation changed?

We've used a gel product called "Grunt", which contains oxalic acid to remove the rust stains on s/s, too, and sometimes made up our own solution for large bits.

One time, after being anchored some miles downwind of a volcano, all our s/s looked brown, but the ocean waves splashing on it washed the brown off. Had me a bit worried. But it was only the "surface rust."

However, when it's your stem head fitting, if you're possibly getting a problem developing, I think the OP was right to ask for input, and I personally would get a buddy to hold the nut while I removed the top two bolts to have a good look-see. Cheap insurance. I can also understand cleaning it up and looking at it over the next few weeks. The deal for me with offering advice is to avoid doing harm, so maybe I'm too conservative from not wanting to cause harm.

Ann

[skipmac]

Originally Posted by Ann T. Cate

The deal for me with offering advice is to avoid doing harm, so maybe I'm too conservative from not wanting to cause harm.

I concur 100% and try to do the same. It is very easy to say "Don't worry, that little rust is just cosmetic" or ""sure, you can buy your first boat and cross the Atlantic a week later, just go for it. But I would feel pretty bad if I said something like that and a week later the OP came online to report his mast went by the boards.

Originally Posted by Ann T. Cate

Hey, guys, stop me if I'm wrong, but I thought the best polishing for Stainless is electro-polishing, done at time of manufacture of the object. And that, after that, the Wichard passivating polish was the best. Has this situation changed?

I do believe you are correct about eletropolishing but in some cases that option just isn't available. The Wichard polish I just learned about in this thread. I have studied passivation a bit in the past but I previously read always used some type of acid bath.