Below waterline fairing compound

jibes138 · May 1, 2017

https://www.jamestowndistributors.c...?pid=6515&familyName=3M+Marine+Premium+Filler

jibes138 · May 1, 2017

Put a coat or two of WEST System epoxy to seal the metal then the filler to fair it.

Crazy Dave Condon · May 1, 2017

The key to metal you have to remove any rust first and then coat it with anything that contains zinc chromate to prevent further rust. Then I used a product or two part epoxy filler called WaterTite which is expensive and a slow cure for fairing out keels. I then applied epoxy paint over it and did the rest of the prop work. Watertite held over the years and worked well at my yards when I had multiple dealerships.

Gunni · May 1, 2017

Both Pettit and Interlux make epoxy-based bottom barrier primers. That will need to go on bare metal. If you want an extra margin of durability paint the bare metal with Ospho, an acid-etching rust neutralizer. Once primed mix up some epoxy with a silica-based filler to thicken it to peanut-butter consistency and carefully fill and fair the pits. You may need to do several coats. Silica thickner (West Cabosil) is designed to not absorb water like the easier to sand fillers but it is some hard stuff, fair it smooth. Finish with 4 coats of epoxy-primer (10mil thickness) applied within 24 hours of one another and apply your bottom paint as a hot-coat (thumb print soft primer). Do it right, you don't want to be doing it again in a couple of years.

sdstef · May 1, 2017

I just did some work to my keel. Hunter 28. Clean metal thoroughly. Wipe down well with acetone or similar. Wet out with west systems epoxy then while still wet, add filler compound until desired consistency, and squeegee over. It is really easy.

Chief RA · May 2, 2017

Gunni: I don't pretend to know the specifics of the procedures here but I do have a background in the field of Plastics. My question relates to his sequence of applying zinc-chromate and then applying epoxy over it. I would think Zinc-chromate would be too soft to properly adhere to an epoxy coating? Seems that zinc-chromate would be applied after the epoxy even if it is supposed to be a rust inhibitor? Chief

Ken Cross · May 2, 2017

Zephyr-Jeffer said:
Thanks all.
I'll attack this first with the grinder wheel, then wire brush, then zinc-chromate primer, then an epoxy coat, followed finally with bottom paint.

I found an angle grinder with a flapper wheel is really effective stripping the paint and rust off. Be sure to wear a respirator and eye protection.

Ken

jibes138 · May 3, 2017

Zinc chromate is for galvanic protection, iron rusting is another problem. Epoxy will seal the metal from exposure to water. If no water then no rust. Zinc chromate on top of epoxy won't do anything to protect the metal since they won't be electrically connected. I'd use two coats of epoxy then a few coats of barrier coat as a primer for the bottom paint, then bottom paint. Each layer applied while the previous one is "hot". The idea is epoxy and barrier coat are waterproof, keep the water away from the iron.

Gunni · May 3, 2017

Whoa there Chief, you're mixing me up with some other cowboy, I would never use zinc chromate for underwater /iron keel repair. I specify an Ospho wash - which is a phosphoric acid solution with the consistency of water that converts any remaining surface rust to iron phosphate, effectively inerting rust prior to epoxy barrier coating. It has no build. BTW, this stuff is great for barn roofs, and implement paint prep.

I have fiddled around with straight epoxy and it is marginally useful in a jury-rig manner. The purpose-designed barrier-coat epoxy primers are superior and about the same price. They have mineral fillers that promote a nice thick coating on your underwater metals. And since these bits are hanging down and vulnerable to banging into stuff you really want plenty of epoxy build. The rule of thumb is a 10 mil barrier coat. 4 to 5 coats of Interprotect, a few less if you use their new thicker barrier coat epoxy Interprotect HS.

Chief RA · May 3, 2017

Gunni: I mean't to be asking your opinion on Zephyrs statement that he was going to apply Zinc- chromate between the metal and the epoxy. Jibes nailed it though in his submittal as I was pretty sure epoxy over paint was not going to cut it. I asked you because you sounded like you knew what to do with the iron keels. My best, Chief

jibes138 · May 3, 2017

My keel is lead and when I first bought the boat on every haulout I had a lot of paint peeling off the keel. I took a belt sander and sanded it down to bare lead followed by two coats of WEST Epoxy, then I used Interprotect and put at least two coats of that because they note it is a good primer for paint adhesion as well as for the additional barrier coating. Then I applied bottom paint. That was about 18 years ago and I haven't had paint peeling off my keel since. The epoxy must be applied as fast as possible since bare metal immediately starts to oxidize. I did one side of the keel at a time to minimize the time spent without protection. I think WEST has some instructions about coating metal keels but haven't looked at it in many years.