Mast Corrosion at Boom Attachment - $$$?

[The Atonement]

Howdy All!

I've been cruising the forums for a long time but this is my first post. I've done my own inspection on a 36' Islander and am getting ready to commission a professional survey before purchase. There's a lot of work I can do myself, but I've found some bubbling of paint (photos attached hopefully) on the mast indicating probable galvanic corrosion. I'm looking for very rough, ball park estimates on how much cost I'm looking at to repair this. I realize without taking down the paint and really figuring out the extent its hard to estimate easily but I'd like some input before I spring for the "real" survey. (For example, if you tell me a new mast is the only option, I won't be paying for a survey on this one since the seller has indicated he is not flexible on his price.)

Basically am I looking at hundreds? A thousand?

I also included a zoomed in shot to show that that's not a crack in the hardware, just some grawdeaux as we say in the gulf.

DH of The Atonement

[model 10]

It looks like the kind of thing you often see on cruising boats. It's hard to keep up with this stuff. It is only starting to look pretty bad. How much do you think it's worth if you were doing it?

[The Atonement]

That's what I'm trying to determine. Is this a boat I want to buy? Is this a job I want to tackle? Is this a job I can afford to pay someone else to tackle?

DH

[svTOTEM]

Inspect other mast fitting for similar bubbling. For proper inspection remove the gooseneck (and any other fitting with bubbling) to see what's underneath and condition of thread/fasteners. If the stainless steel was not isolated from the aluminum it good be ugly. If bubbling limited to this spot and underneath is good, scrape away bubbled paint. Then isolate gooseneck (all dissimilar metals really) with UHMWP or Duralac and TefGel on fastener threads.

[model 10]

It depends. Some people get someone else to do their varnish. The corrosion you show looks just like the stuff everybody deals with. It's not that that big of a deal. Do you want to do this kind of thing yourself or do you want someone else to do it? How much are you willing to pay someone to remove all that stuff and fix everything? Some places would charge $100 an hour others $5. Figure a boat buck ($1,000) and you should be safe.
I seriously doubt there is any serious damage to the mast.

[The Atonement]

Cool, thanks.

I know that corrosion is just one of those (many many many) things that you just have to deal with, I was just worried with the sudden and catastrophic damage if a mast goes down. Corrosion nearly anywhere else is less problematic.

I don't mind pulling the gooseneck, scraping and repainting, insulating etc etc. I just wanted to make sure I wasn't looking at having to get a welder to fill holes or ar attach some sort of plate to bolster it. NOW clearly if there is a huge void behind the gooseneck that'd be a different story.

Thanks

[DeepFrz]

Its hard to tell the extent of the damage but it looks like the seller has painted the mast to, perhaps, hide the extent of the corrosion. A surveyor will be able to tell you the extent of the damage but its very difficult from 2 photos to really know what shape the mast is in.

[mstrebe]

Concur that you'll have to take the gooseneck off to inspect. Honestly it doesn't look that bad to me. You might want to re-tap the next larger-sized screw if the threads in the mast are heavily corroded.

The biggest issue to clear is not whether or not there's surface corrosion between the stainless gooseneck and the mast, but whether or not the mast has corrosion resulting in cracking at the boltholes. Those kinds of cracks dramatically weaken the mast and can act as a "tear tab" that can allow the mast to break right there. Older aluminum masts commonly break at the spreaders because of this problem.

Drives me nuts that some manufacturers ship boats with stainless bolted directly to aluminum with no galvanic isolation.

[skipmac]

Making a WAG from the photos the corrosion probably isn't serious at all. Have seen a lot of this and only rarely was it extensive enough to weaken the mast.

However, it is almost certainly a result of galvanic action between the stainless fittings and the Al mast. Which means there is a very high probability that all the SS bolts are permanently bonded to the Al and a lot of them will break when you try to remove them.

The repair is fairly simple, remove all the SS bolts and fittings, put pads under all the fittings and coat all the bolts with the proper goop (like Tefgel) and reinstall. The actual implementation will probably be a very annoying pain in the posterior. Before starting the job read one of the many threads on this forum about how to remove SS bolts from Al fittings. A hint, PB Blaster (or Kroil) and heat are your friends.

[skipmac]

Originally Posted by mstrebe

Drives me nuts that some manufacturers ship boats with stainless bolted directly to aluminum with no galvanic isolation.

Some? How about most. Incredible stupidity in my book.

[The Atonement]

Originally Posted by mstrebe

Those kinds of cracks dramatically weaken the mast and can act as a "tear tab" that can allow the mast to break right there.

That's the most specific of my fears. Right where the gooseneck acts as a fulcrum of forces is the place I would be most worried about weakness.

I appreciate all of the suggestions on products such as tefgel for prevention. I've heard of using that on the SS screws, but do I just smear that behind the gooseneck as well or is there a recommended intermediary "gasket"-type material to actually insulate between the two metals?

[mstrebe]

Yep, just smear it all over inside surface of the SS fitting and install using bolts coated with it.


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[meirriba]

Everything will become clear once you remove the screws and see the mast behind the gooseneck. It may be clean. On the other hand the gooseneck may hide a hole the size of itself. No point in guessing.
When re-installing, you may cut to shape and size a piece of plastic film and put it between the different metals.

[pitlaw]

I just repaired a worse looking area of corrosion. Use a power tool with a teflon or similiar material to grind off the paint and corrosion to bare aluminum. Dont use wire brush-disimiliar metel fragments. Then wash with acid and then alodine to protect the bare aluminum. Then paint a base coat of chromate on then final coat. These products can be found on thr net.
From your pictures your corrosion is really minimal and you will realize once ypu take out yhe screws thatbyour mast is thick and probably still solid. There are more detailed threads that describe this process.

[skipmac]

Originally Posted by pitlaw

I just repaired a worse looking area of corrosion. Use a power tool with a teflon or similiar material to grind off the paint and corrosion to bare aluminum. Dont use wire brush-disimiliar metel fragments. Then wash with acid and then alodine to protect the bare aluminum. Then paint a base coat of chromate on then final coat. These products can be found on thr net.
From your pictures your corrosion is really minimal and you will realize once ypu take out yhe screws thatbyour mast is thick and probably still solid. There are more detailed threads that describe this process.

Exactly the way to go.