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Old 29 August 2015, 19:28   #1
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Rust bleed

Due to one of the jockey seat backs snapping, I had to remove them to swap them around a while back. I was disappointed to find that the reason I was suffering from rusty marks down the back of the seat pods was that none of the holes where the bolts went through were sealed - nothing at all. Sadly quite a lot of attention to detail was lacking when the boat was fitted out (not by the current Osprey dealers, I hasten to add) so it wasn't a complete surprise to find this.

The seat pods, and I guess probably various other fittings, seem to have mild steel plates set inside the GRP as strengtheners. I presume the rust bleeding from the holes is due to salt water ingress corroding the plates, so it isn't marine stainless as there is nowhere else rust could come from - the bolts are perfect.

At this stage I don't think there is really anything I can do about it short of major surgery to cut the plates out and replace them, which is completely out of the question and in any case there is no sign of weakness, it's just cosmetic at the moment. I think my plan is to spray some WD40 in to try and inhibit the corrosion, seal it all up with white sealant when I put the new seat frames on, and hope for the best. It will probably be years before it becomes a major problem.

More of a concern is that the bow eye is also suffering from the same sort of rusty staining, probably for the same reason. This is a bit more important in structural terms especially when on the trailer!

My question at the moment is what the reinforcement plate for the bow eye actually looks like and how it's moulded into the GRP of the bow? Would it also be mild steel - or stainless? I guess it must be a V shaped plate but I have no idea how big it would be. I presume there are nuts somewhere up in the top of the anchor locker but the jockey console is well forward so I don't really know if I can get my 'ample frame' in a position where I can see/reach them and I've not emptied it to look yet.

Should I be concerned about this? Any thoughts welcome.
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Old 30 August 2015, 03:39   #2
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If you have saltwater contact with encapsulated stainless fittings then you may have this: Topic Category: Category: Crevice Corrosion
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Old 30 August 2015, 04:13   #3
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I'm with Wilks on this sounds quit normal on stainless fittings around the boat!
Do you have any photos, I just go round with a bit of Oxalic acid once a year to tidy it up!
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Old 30 August 2015, 04:28   #4
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Yip... quite common. The question is how do you know if the component is about to fail, as surely at some point the corrosion will eat enough of the metal that it may fail under load?

Clearly if it starts to be loose it needs investigation. But is there anything else that could be done as an inspection?

I've note come across metal embedded into fibreglass - rather wood. So the structure in cross section from the outside would be something like: Component - GelCoat - CSM/Resin - Wood - CSM/Resin - Washer/Backing Plate - Nut(s)

From my experience is doesn't seem to matter if you fill the drilled hole with silicone before pushing the component through and bolting it up. Some rust still creeps through. If your component has a flat surface against the gel then sikka might be better at stopping the rust creeping - but not 100% sure that doesn't mean you just can't see the problem! Something like this:

Wichard U Bolt Watertight | Mailspeed Marine

I'd want to be sure the nuts couldn't be getting wet from other sources... like the anchor locker!
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Old 30 August 2015, 04:57   #5
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OK, so you reckon despite the rust, the plates inside the seat pods will be stainless not mild? In that case I guess it is just a cosmetic problem (phew!). I did think it was odd to use something that could rust on a boat...

I doubt very much whether I can get any oxalic acid here unless it's in a household product (will go and talk to Google shortly!), but the mess on the gelcoat cleans off with wax polish and a bit of elbow grease.

I presume there would be no point in putting Kurust or similar around the holes (this is excellent on mild steel rust but the chemical process is probably completely wrong for stainless?) - is there anything worth putting on/in to help inhibit?

Anchor locker: the anchor is never used (emergency only) and I always open the locker and seat pods to let it all air out when the boat is in the garage, so it's not really going to be damp in there.
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Old 30 August 2015, 04:58   #6
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Stainless will rust & don't let anyone convince you otherwise. Clean it up with scotchbrite & wd40 & stop worrying.
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Old 30 August 2015, 06:51   #7
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Sir, Yes Sir!
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Old 30 August 2015, 06:54   #8
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I should also say that both the new seat frames, and the replacement seat cushion, are a vast improvement on the originals.

Thanks Chris
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Old 30 August 2015, 07:13   #9
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Oxalic acid is used as a cleaning product / bleach, and is in some proprietary products for stain removal. You might find some in a traditional hardware store / ironmonger or chemists shop if you have such things on the islands.
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Old 30 August 2015, 07:19   #10
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A squirt of Clit Bang or similar and a scotchbrite pad will prob shift it.
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