Cleaning up a cast iron keel

Charlie Jones s/v Tehani · Feb 3, 2017

I've used Coal Tar epoxy on my cast iron keels for years now. Wouldn't dream of doing anything else. Coal Tar, Interprotect 2000E, then bottom paint.

I usually get 3 years out of a bottom job, but then we have 3 storm drains that dump into the marina, so not a lot of barnacles

Brian S · Feb 3, 2017

Justin_NSA said:
A friend of mine in our sailing club wants to go in on renting the sand blasting equipment for a day. Any idea how long it takes to blast a shallow draft keel? We would both need time to get it primed before they start to oxidize again. We'll be doing it in early Spring so the temps stay high enough to let the primer cure

The first coat of Ospho Phosphoric acid will take care of that. Reacts with iron oxide to form iron phosphate, much more inert.

SwitchintoglideIII · Feb 3, 2017

Brian S said:
The first coat of Ospho Phosphoric acid will take care of that. Reacts with iron oxide to form iron phosphate, much more inert.

+1

Gunni · Feb 16, 2017

You can do a bunch of the prep (digging out spalled rust spots, loose coating, wire brushing) a head of time ospho coat, then start early the day of epoxy, wire brush those spots again, paint them with Ospho, give it time to dry and then start with epoxy. It just takes longer to set up. If you use Interprotect there is a pretty liberal recoat schedule that would allow you to pick up again the next day.

jibes138 · Feb 23, 2017

Get a roll of cheap plastic and tape it to your hull to encapsulate your work area, put tarps on the ground and use rocks or boards to hold the bottom of the plastic down. Then you can work inside the plastic enclosure and contain any pollutant dust. You can also use a space heater inside to keep the temp over 50 degrees so you can use epoxy on the keel. I sandblasted a house one day and did two sides of the house in one day. You should be able to sand blast a keel in about an hour. Tape off the keel joint and above it with a lot of hard rubber and duct tape, you don't want to hit the glass area of your boat, sand blasting will drill a hole right through it. Another option to try instead of sand blasting is using a belt sander. I stripped my keel on my 35 (lead keel) with a belt sander and sealed it with epoxy. Only took maybe half a day to sand the keel to bare lead. I did each side separately so the lead was not exposed to atmosphere for any length of time before coating with epoxy. If you have deep pits in your iron sandblasting is the way to go, the belt sander will strip paint and epoxy but won't take much metal or reach into pitted areas like sandblasting will.

jibes138 · Feb 23, 2017

On top of renting the equipment you also have to buy sand. Sand blasting is very aggressive, it goes quick. On wood shingles I couldn't dwell at all or it would drill a hole in the wood. You will spend a lot more time setting up the equipment, getting the compressor running, putting on safety gear, filling the hopper with sand, taking it all down and cleaning up afterwards. The actual sandblasting time will be very short. You do not have much surface area and paint will blast off very fast. You can buy a lot of belt sander belts or sanding discs for 400 bucks along with the sanders.

jibes138 · Feb 23, 2017

Hey, you can BUY a sandblaster rig for only 129 bucks at Harbor Freight or on amazon and just rent a compressor to run it. Should be a lot cheaper than 400 bucks. http://www.harborfreight.com/110-lb-pressurized-abrasive-blaster-60696.html
A compressor is another 129.00 bucks on amazon https://www.amazon.com/PORTER-CABLE...qid=1487886296&sr=8-3&keywords=air+compressor
A few 5 dollar bags of sand and a safety hood and respirator and you'll have cash left over. For the cost of renting it you could toss the whole mess in the dump when you are done and still have cash in your pocket. Or you could start a business blasting keels for all your buddies at the marina.

Barn-dog · Feb 24, 2017

I just had the iron keel on my Hunter 34 soda blasted. It must be done correctly, so I let the marina do it. After blasting it, they immediately applied two coats of Petit Rust Lock epoxy. Then they dug out the void between the keel and the hull and filled/faired it. It's a big job; cost me close to a thousand.
Barn-dog

Warren Milberg · Mar 27, 2017

If you search this site for "cast iron keel" you'll get enough reading material and advice to keep you busy until next year....

In the case of my cast iron keel, I like to keep maintenance simple: (1)sand as much as possible. (2) clean up dust with acetone. (3) apply a couple of coats of Interlux Primocon or the Petit Rustlok you mention - it hardly matters which one. (4) bottom paint with Hydrocoat and, most importantly, get the boat into the water and go sailing. Unless you are an OCD-type racer, I would not go to all the trouble/cost involved with sandblasting, rushing to get a barrier on before surface rust reappears, and trying to get a perfectly faired keel. Go for good enough and sail more....

isaksp00 · Mar 27, 2017

The grey layer might have been POR15, which is what I used on my 23 iron keel. It looks sort of like grey porcelain (hard and shiny) after you apply it.

JRacer · Mar 27, 2017

Bondo? ;-)

Gunni · Mar 28, 2017

Do yourself a favor and contact the guys at POR15, tell them you intend to coat the cast iron keel of your sailboat and need their endorsement of that application. The company recommendation for use of POR15 on underwater metals disappeared years ago ....but linger on in the intertoobs. The number one reason people bad-mouth iron keels is because they do not properly maintain them.