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 Post subject: Rust from rub rail
PostPosted: 19 Jan 2016 17:35 
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Rail Meat

Joined: 27 Apr 2008 18:41
Posts: 23
Does anyone know what is causing the rust from the rub rail?
It doesn't appear to be rusting screws or bolts.
Not sure if its coming from the stainless rail itself or from beneath it.


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 Post subject: Re: Rust from rub rail
PostPosted: 20 Jan 2016 00:45 
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Skipper

Joined: 21 Jan 2010 12:57
Posts: 168
Not at all sure, but most likely from the fasteners. There are several on the boat that I have custody of that weep a bit. Tartan perhaps used 18/8 screws, or perhaps tiny remnants of the drill bits used in creating the holes in the s/s strip?


 
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 Post subject: Re: Rust from rub rail
PostPosted: 28 Jan 2016 12:40 
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Able Bodied Seaman

Joined: 27 Jun 2007 11:23
Posts: 40
Hello;
In my case; rust was from fasteners and also from the back of the rub rail (wich I replaced along with all the fasteners last year).
Stainless will rust eventualy when it's not il contact with ambiant air; as it is the case for the fasteners embedded in the butil joint and parts of the back of the rubrails.
Sailing in saltwater in warm climates promotes rust even faster.

Regards;

Jean-Denis

_________________
S/V NEMEA
Hull #162
YCQ, Qu?bec City, QC, Canada


 
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 Post subject: Re: Rust from rub rail
PostPosted: 03 Feb 2016 09:21 
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Skipper

Joined: 21 Oct 2006 15:36
Posts: 268
Well, I've had a lot of experience with this problem on my boat and I'll pass on what I know.

I've attached a series of pictures documenting my boat's condition. The first picture shows the rust streaking on my boat. It is actually worse than shown. I removed the aft port and starboard sections of my rub rail to see what's going on. The next picture shows the pasty 'muck' captured behind the rub rail at the toe rail drain slot locations. As you probably know, the rub rail is convex shaped, and at the toe rail slot drains the upper portion of the rub rail overlaps the deck with a gap that exposes the back side. Because of the overlap, the drain water and 'muck' can pass behind the rub rail and collect. When I removed the rub rail, the 'muck' was still moist even though the boat had been on the hard for a few months. The next picture shows the distinct rust line left on the hull after the 'muck' was wiped off. The next picture shows the backside of the rub rail immediately after I removed it from the boat. To my surprise, there was only very minor rusting on the back side. However, I did note that there was some pitting on the lower edge of the rub rail, which indicated to me (my guess) that this corrosion (pitting) was caused by the lack of O2 at those sections because they were blanketed by the 'muck.'

From all this I concluded that the major source of my rust streaks was not the backside of the rub rails. It was also not caused by the screws which I replaced a few years back with 316SS. Some rust streaks did come from a few screw holes on the rail, but the screws themselves showed no evidence of rusting.

My theory is that the 'rusting' is being caused by the 'muck' trapped behind the rail. I believe this because the 'muck' could easily cause the O2 pitting. Also, the streaking became much more problematic after I installed my seawater deck wash pump, which I use primarily to wash the 'muck' off my anchor/chain. I seems very probable to me that the 'muck' I found trapped behind the rub rail is the same 'muck' that I washed from my anchor. Now this next part can be a little crazy, but here it goes. I sail in the Cape Cod area. I did a little research, and the soil in this area is high in iron oxide, and contains a lot of rust colored organic matter, which is very leachable. Perhaps the rust streaks are caused, in part, by the rust colored material leaching from the 'muck.' Anyway, regardless I'm going to try to prevent the 'muck' from getting behind the rub rail. The last picture shows the back side of a rub rail at the location of the toe rail drain slot. I filled the back side with thickened epoxy, which I sanded flat. My intent this Spring is to do the same at the mating location at the hull. I'll apply some sealant to these surfaces when I mount the rail, hoping that the seal will hold and this will prevent the 'muck' from the toe rail drain from accumulating behind the rub rail. I'll let you know this Spring how things work out.

Good luck. Hope this is useful.


Attachments:
File comment: Rust streaks on hull from rubrail
2015-12-10 12.33.01.jpg
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File comment: Pasty 'Muck' left on hull at toe rail drain slot after rub rail was removed
2015-12-11 12.27.23.jpg
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File comment: Rust line left on hull after 'muck' was removed
2015-12-11 12.28.09.jpg
2015-12-11 12.28.09.jpg [ 731.92 KB | Viewed 0 times ]
File comment: Back side of rub rail directly after it was removed from hull; no significant back side rusting evident
2015-12-11 12.28.52.jpg
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File comment: Thickened epoxy sanded flat on back side of rub rail at toe rail drain location
2016-02-03 08.24.24.jpg
2016-02-03 08.24.24.jpg [ 1.55 MB | Viewed 0 times ]

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Jim Voelxen
Odyssey #191
Home Port: Osterville, MA


Last edited by jvoelxen on 15 Feb 2016 20:58, edited 1 time in total
 
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 Post subject: Re: Rust from rub rail
PostPosted: 05 Feb 2016 23:39 
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Skipper

Joined: 29 Dec 2006 09:38
Posts: 656
I have some streaks too. My boat has spent most of its life on San Francisco Bay where I had only a hint of a problem. Then two years in Central America coming to Maine 5 years ago (this is where I started to really notice it) and now in Penboscot Bay where I have been fighting it with oxalic acid. I was thinking that the worsening was just age. I like your theory and effort. keep us advised of your outcome.

Ray
Velera #373


 
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 Post subject: Re: Rust from rub rail
PostPosted: 16 Feb 2016 23:16 
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Rail Meat

Joined: 27 Apr 2008 18:41
Posts: 23
@jvoelxen - thanks so much for taking time for your write up.

I think you might be on to the problem as the streaks seem random, at least for me.
I was going to replace the rub rail but after reading your response I think I will concentrate more on cleaning behind and preventing 'muck' from being trapped. As for the pitted areas in the rub rail itself I would hit with Ospho.com (removes the rust stain as well), good stuff!


 
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 Post subject: Re: Rust from rub rail
PostPosted: 09 Apr 2016 14:19 
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Skipper

Joined: 21 Oct 2006 15:36
Posts: 268
An update on my rub rail rusting issue.

I removed all remaining sections of my rub rail this Spring. See attached picture. There is a distinct rust line that matches the bottom of the rub rail for the entire length of the rail on both sides. Also, surprisingly, the sharp edge of the rail has cut a slight groove in the gel coat of the bottom side. The sharp edge of the rail's top side has also cut a grove into the teak toe rail, but being wood that didn't surprise me as much. It seems like the rub rail was installed too tight which caused it to cut the grooves. My guess is that some sea water makes its way behind the rail, which causes some minor rusting, which is probably inevitable. This situation is in addition to the mechanism I described in detail in my previous post. Then, water containing rust will run down along the bottom of the rail, and, in time, will rust stain the groove. Just a guess. To prevent this, I'm going to lightly sand the grove in the gel coat to make the area flush. Then, if possible, install the rail more loosely hoping that any trapped water will be allowed to drain, without running the length of the rail. Not sure it can be done, but will try.


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2016-04-09 14.19.57.jpg
2016-04-09 14.19.57.jpg [ 694.75 KB | Viewed 0 times ]

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Jim Voelxen
Odyssey #191
Home Port: Osterville, MA
 
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 Post subject: Re: Rust from rub rail
PostPosted: 16 Dec 2020 00:28 
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Skipper

Joined: 25 Apr 2016 10:25
Posts: 185
I started pulling the rub rail today from the bow of the boat. We also have the rust stains that reappear. I was going to replace the screws with 316 stainless ones since I have a few hundred 1 inch screws on hand. It looks like a bunch of gunk builds up behind the rub rail and this causes moisture to stay back there rusting the rail. When reassembling did you caulk the entire rub rail or did you reinstall dry? Should I apply some sealant to each fastener e.g. 4000UV?


 
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 Post subject: Re: Rust from rub rail
PostPosted: 16 Dec 2020 00:43 
Offline
Skipper

Joined: 25 Apr 2016 10:25
Posts: 185
I started pulling the rub rail today from the bow of the boat. We also have the rust stains that reappear. I was going to replace the screws with 316 stainless ones since I have a few hundred 1 inch screws on hand. It looks like a bunch of gunk builds up behind the rub rail and this causes moisture to stay back there rusting the rail. When reassembling did you caulk the entire rub rail or did you reinstall dry? Should I apply some sealant to each fastener e.g. 4000UV?


 
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 Post subject: Re: Rust from rub rail
PostPosted: 16 Dec 2020 07:44 
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Skipper

Joined: 09 Aug 2017 15:35
Posts: 725
Location: Maine/USVI
I took off the entire rub rail, dug it out and cleaned it. The hull deck joint is put together with butyl and underneath the stainless was filled with copious amounts of polysulfide. Once cleaned, I taped it off and re-filled with polysulfide, let it cure and put all the screws back in. I didn't have 316, and since it's only trim, I used 304 (18-8). I found I needed some 1.25" screws here and there to catch anything, since it IS in a gap. Once cured, the polysulfide will hold an errant screw. Actually, I think I went up on size on diameter, too. Check the taper to make sure the head fits cleanly on the stainless rub rail.

I cleaned the heck out of the stainless, got any rust stains off and waxed it front and back before re-installing. It's nice to have a platform and a couple loops of line to hang the far end of the stainless piece while you start the first screw or two.


 
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