Painting shaft / rudder

Maine Sail · Mar 26, 2010

Mike G. said:
A few years ago, based on many of your recommendations I painstakingly removed the hard bottom paint from my SS shaft and bronze prop that the PO had applied.

Now, Sail's most recent issue has a write up in the Boatworks section by Nigel Calder where he recommends painting the shaft and rudder.

It sure would be nice to have a shaft and rudder free of barnacles. Looking around the yard, I'd say that about 25% paint them. Waddya think?

Mike

Mike,

I read that too and was very surprised to read that Calder has had no issues using Trinidad. He does mention that other folks have had issues as have I.

It's fine if you use the right paint. You'll want a paint safe for underwater metals or for metal boats. I would not personally use copper based paint for underwater metals despite Calder's recomendation ut then again I am one who has paid the price. I have a prop in my barn that shows why..

This is dezincification of a bronze prop where the zinc has been eaten out of the bronze leaving behind only the copper. No prop shop will not even work on it due to liability. This happened because the PO hit a NO DIY yard in Florida and the yard monkey painted the shaft and prop without asking. It had been fine for 20 some odd years, unpainted, and this was what a half a year of copper bottom paint did to it.

If you use the right paint and you'll be fine..

sailingdog · Mar 26, 2010

It is probably a zinc-based anti-fouling paint.

redhead78 · Mar 26, 2010

how about the Pettit zinccoat barnacle barrier 1792, spray. Is this stuff any good????

Don S/V ILLusion · Mar 26, 2010

I have used Pettit Zinc coat for the past 3 seasons in New England and can attest to it's efficacy at minimizing growth on the prop and shaft. In terms of cost, I still have half the can left.

jibes138 · Mar 27, 2010

I was looking for some prop paint last weekend but none of the marine stores carried anything except some aluminum piant called T33 or something. I threw a coat of Micron ultra on the prop and shaft as I figure it won't last long. Propspeed in the West catalog was about 200.00 but they don't have it in the stores. What paints are available for this purpose?

sailingdog · Mar 27, 2010

Still not a good idea to put Micron ultra on a bronze prop. Electrolysis damage is cumulative...

jibes138 said:
I was looking for some prop paint last weekend but none of the marine stores carried anything except some aluminum piant called T33 or something. I threw a coat of Micron ultra on the prop and shaft as I figure it won't last long. Propspeed in the West catalog was about 200.00 but they don't have it in the stores. What paints are available for this purpose?

John T1594 · Mar 27, 2010

Use Primer under the paint

I have used the same method for the past ten years and never have more than one or two barnacles on my prop or shaft. I clean the stainless steel shaft and bronze prop down to clean metal with a wire brush on an electric drill. Wipe with solvent and apply two coats of a non-metallic primer. I have used Interprotect successfully but other non-metallic primers work as well. I then apply two coats of any available copper based bottom paint and splash the boat. Don't prime or paint under or over the zincs. As I said, little to no fouling after six+ months. I use the boat almost every weekend and motor perhaps for 30-60 minutes total each time we take the boat out. By the end of the season, the paint has worn off the tips and parts of the prop blades but is intact elsewhere.
I have tried this method without the primer and always got bad fouling of the prop and shaft. Interlux outdrive spray works well if used with their primer but is more expensive. I have heard others theorize that the electrolysis current set up between the metal shaft/prop and plain copper paint somehow keeps the copper inactive and thus allows barnacle fouling. A non-metallic barrier coat of primer stops this interaction and allows the copper to inhibit growth.
I sail in the salt waters of Barnegat Bay NJ and keep the boat in Forked River - a somewhat brackish river feeding the bay.

BobM · Mar 28, 2010

I used generic cold galvanizing spray for $12/can

Don S/V ILLusion said:
I have used Pettit Zinc coat for the past 3 seasons in New England and can attest to it's efficacy at minimizing growth on the prop and shaft. In terms of cost, I still have half the can left.

Most of this stuff is 90+% zinc, so the rest of it can't be doing much, except evaporating. One key is that you need to wet it down for 30-60 seconds after your last coat. Seems to change it somehow.

Tried it for the first time last season. Definitely minimized barnacle growth. The prop and shaft are still well coated (the stuff dries at 90+% pure zinc).

Don, have you ever cleaned back down to the metal to see if it is affecting anything? Might be a public service if you did so. I can do so, but you have been doing this for a longer period of time and have a better data set. I am not suggesting to clean the whole thing, just a small patch on the prop so we can see if it apears to be leaching anything. I will do so too. Barnacles area PITA and there doesn't seem to be a good solution out there other than the $100 two part Interlux product. After reading spotty reviews on that I thought about the cold galvanizing, which I bought to treat some steel backing plates I made for the bow cleats on my old boat. I just thought that, given I was bolting a zinc on their anyway a layer of sacrificial zinc on the whole thing might do some good too. I didn't know Pettit even sold it at the time. I even considered marketing it myself, but decided it would be too much work given the government red tape.

LloydB · Mar 28, 2010

BobM said:
Most of this stuff is 90+% zinc, so the rest of it can't be doing much, except evaporating. One key is that you need to wet it down for 30-60 seconds after your last coat. Seems to change it somehow.
Wet -with what? how do you get the last coat on in less than 60 seconds? what happens if not done?

Don S/V ILLusion · Mar 28, 2010

BobM said:
Don, have you ever cleaned back down to the metal to see if it is affecting anything? Might be a public service if you did so. I can do so, but you have been doing this for a longer period of time and have a better data set.

Bob
Ordinarily, I'd be eager to do as you suggest but it's a bit impractical now as I'm in Fl and the boat is in RI and I'm planning it to splash before I get up there to try this.

Having cleaned and re-sprayed the prop each of the last 3 seasons, my casual observation is there was no discoloration indicative of dezincification or any other issues except for some pitting along the prop blade edges attributed to my previous galvanic corrosion problem that occurred prior to using the Pettit paint and has not gotten worse.

I know many other folks both locally and elsewhere use the same prop paint and none have ever indicated any problem for what that's worth...

Warren Milberg · Mar 28, 2010

I don't think there is a good solution to keep your prop and shaft free of hard growth. Propspeed may be the "best" there is, but it's too expensive for my budget. I've been using the Petit Barnacle Spray for a few years and it seems to keep hard growth to an acceptable level. I usually put on 2 coats and by haul out time it is mostly gone. I also usually have some hard growth by then, but not enough to cut down performance noticeably. Everthing about boats is a compromise.

BobM · Mar 30, 2010

Instructions

LloydB said:
BobM said:

Most of this stuff is 90+% zinc, so the rest of it can't be doing much, except evaporating. One key is that you need to wet it down for 30-60 seconds after your last coat. Seems to change it somehow.
Wet -with what? how do you get the last coat on in less than 60 seconds? what happens if not done?

Click to expand

The instructions on the can said to immerse it in water after the last coat, which was impractical, so I just hosed it down. I presume it is just to wash away any of the carrier solvents to make the coating more uniform. I don't have the can handy, but as I recall I just followed the instructions on it. These may have been specific to use on parts to be immersed in water. I looked but couldn't find a recommendation on line from other common suppliers.