Restoring Iron Keel - Belt Sander?

Justin_NSA · Mar 9, 2015

I would think that a random orbital sander would be better than a belt sander. I have no experience but sandblasting would seem to be the best way. There will be a lot of harmful airborne particles any way you do it.

justsomeguy · Mar 9, 2015

PDReynolds said:
snip-

Previously I have used an angle grinder with various wheels of sandpaper and wire, but the angle grinder is very difficult to use.

Has anyone attempted to use a belt sander to clean an iron keel down to bare metal? If so any suggestions would be helpful.

Thanks,
Peter

What do you find difficult about the grinder approach?

I've used an angle grinder with the flap-disk on my keel, with very good results.

Gunni · Mar 9, 2015

Don't know where you plan to do this work, but your bottom paint is considered hazardous, and flinging it willy nilly is a violation of waste management law. Commercial boatyards prohibit violations. You could tent and contain the dust with air flow management, or use a pad sander with a vac attachment. It is not necessary to remove paint and barrier coat to metal where there is no corrosion. And doing so requires that you immediately coat the bare metal before the surface can oxidize. A pad sander works well to get the coating removed, and a wire brush burnishes the metal for application of the barrier coat. If you get the paint off you can make sure that your barrier coat is up to snuff, and repair any rusty boils. There is no permanent fix, there is only regular maintenance on an iron keel.

Brian S · Mar 9, 2015

A guy on trailer sailors forum re-did his swing keel. Lots of pits. He tried a smaller sandblaster and got nowhere. Then he got a flappy wheel, I think. A lot of people suggested a needle gun.

Warren Milberg · Mar 9, 2015

Having lived with, and maintained, a boat with an iron keel for many years, I think it would be near impossible to sand the surface of it down to bare metal with an orbital sander even using 40-grit disks. I think a better way to deal with these keels is to just assume that you'll have to do about an hour of maintenance on it each spring. For me, that consisted of sanding the rust bleed-thru spots and then rolling on 3-4 coats of Interlux Primocon prior to regular bottom painting. No big deal.

Capt jgw · Mar 9, 2015

If its pitted you'll have to remove s heck of a lot of material to get the pits out. Not only a lot of work, but will remove quite a bit of weight. On commercial steel boats, we don't attempt to do this. Just remove the paint and loose rust, then paint with phosphoric acid (OSPHO) which you will find in the paint department at Home Depot and the like. Paint it on with a chip brush, dabbing thoroughly onto the pits. Let it dry overnight, keeping it dry, then wipe down with a compatible solvent then barrier coat or paint. OSPHO turns iron oxide into iron phosphate which takes and holds paint nicely. Works on anything with rusty steel; cars, trailers, anything.

Captn TJ · Mar 9, 2015

PDReynolds said:
Hi All, My 2006 Beneteau is in need of a keel re-work this year. I am planning on getting the keel down to bright metal and then applying epoxy barrier coat. I have tried in other years to get local firms complete the job by sandblasting, but none seem interested. Previously I have used an angle grinder with various wheels of sandpaper and wire, but the angle grinder is very difficult to use. Has anyone attempted to use a belt sander to clean an iron keel down to bare metal? If so any suggestions would be helpful. Thanks, Peter

Do you really want to take on the entire keel? Unless you have it soda blasted it will be a significant challenge. My recommendation (have done this on my 423). Is to pop off the loose/delaminated epoxy, wire brush (grinder wheel) wipe with solvent and primocon immediately after. You can then fair it with a thickened epoxy and several coats of interlux barrier coat.

Popping off the loose stuff is pretty easy with a combination of tapping with a small hammer then using a small drywall Knife or 5 in 1 tool to lift off.

capta · Mar 9, 2015

I should think that a chipping hammer and a wire wheel in a drill would be by far the easiest (and cheapest) way to clean up your keel. There are even mechanical chipping machines or sand blasters you can rent if it's really bad, but grinding seems way too much cutting and work to me.
The most important thing is to remove all metal dust from the pores of the metal and immediately get phosphoric acid or a primer on the shiny metal. After a very short time (hours, not days), the metal will begin to rust again, so anything over that will not adhere well. Do small sections at a time, cleaning and priming, then move on. After the whole keel is primed and dry, you can fill and fair if you wish, to get a really nice surface.
Most primers have data sheets which should give you excellent directions for preparing the metal to be primed.

Ron20324 · Mar 9, 2015

I've used a belt sander with good results. Yeah, there's alot of material on the keel. Even if you used a grinder, you'd probably want the belt sander to take down the remainder so it's smoother. I like the flappy wheel idea, though. I'm hauling in May and will try it. Stand by for results.

Charlie Jones s/v Tehani · Mar 9, 2015

I've dealt with two cast iron keels.

Sand what you can with a flap wheel, then coat the keel with Ospho, wihich chemically converts the rust. Then use some barrier coat like interprotect2000. Then paint

rgranger · Mar 10, 2015

I've done this....

Would not want to do it again. But if you are going to do it.... I started with a sander... but with deep pits... was not going to finish in my lifetime. So I went to a needle gun. It sort of worked to get the light stuff off but the air hammer (see pic) really did a good job of getting the scale off. Then I sandblasted. I purchased a portable unit from Harbor Freight. It worked well enough. I used crushed slag instead of sand. The sand kept clogging my jet. Then rust treated and faired with thickened epoxy. Two barrier coats then painted.

It was a TOTAL PITA.

But I learned a lot.

py26129 · Mar 10, 2015

A knotted wire cup brush on an angle grinder does a great job of removing old paint, rust etc. etc.

http://www.blattsbargains.com/prod_images_blowup/B3MPHqQ2kKGrHqFiEEqtYBKCeBMlU0OJhg_3.jpg

Cheers

Matt

Brian S · Mar 10, 2015

For the OP, if you do get down to bare cast iron, you might consider the phosphoric acid to get a coat of iron phosphate, then coating with several coats of coal tar epoxy (as used on steel ships, buoys, etc.) THEN do your fairing with a product designed to be under water, and then coal tar epoxy over that. During fairing, if you burn through your first layer of CTE, re-phospate and CTE before continuing your fairing. You want that phosphate and CTE on the metal, otherwise water will get under anything else. Also, I have heard that where rust scale expands something like 8x volume, it does not lose all that much weight, so don't worry about your keel getting too light.

seadaddler · Mar 10, 2015

Wire/grinder

A wire cup brush on a side grinder is out of this world but
use protection like face and gloves before starting and it will
go to bare metal for sure than some kind of interlux barrier coat.
Nick

Restoring Iron Keel - Belt Sander?

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