I was once put of for the initial cost was prohibitive. Later I somehow got a tabernacle mixed up with a large amount of steel fittings, and had it for free so they did not have the nuisance of writing a bill. Nowadays I will go to a steel worker and let him handle it.
Steel CB protection
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Re: Steel CB protection
I was once put of for the initial cost was prohibitive. Later I somehow got a tabernacle mixed up with a large amount of steel fittings, and had it for free so they did not have the nuisance of writing a bill. Nowadays I will go to a steel worker and let him handle it. -
Re: Steel CB protection
You don't have to pay that much for galvanizing. Find welding and metal fabrication places. They store up projects that need it until they have a bin full, then get it all done at once.
Have yours added to the batch.
I did this 10 years ago when I replaced Drake's CB. Worked great and cost squat.Comment
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Re: Steel CB protection
I've had two boats with iron keels. Both were primed and painted originally and held up well. On one I scraped scaled and sanded it by hand, primed with zinc paint, and copper bottom painted. That was over 20 years ago, it still looks good. I have no doubt that galvanizing is best, but many thousands of steel ships travel the world with no more than paint and primer on the hull. Many many classic boats have iron keels that are just painted too.Comment
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Re: Steel CB protection
Cast iron ballast keels and mild steel corrode at vastly different rates.It really is quite difficult to build an ugly wooden boat.
The power of the web: Anyone can post anything on the web
The weakness of the web: Anyone can post anything on the web.Comment
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Re: Steel CB protection
Don't forget the zinc anodes or impressed current systems on those thousands of ships:
Zinc rich paints:
1. Zinga Organic epoxy primer 96% Zn
2. Zinc Clad IV Solvent-based 85% Zn
3. Zinc Clad XI Water-based inorganic Zn silicate with no VOC and 90% Zn
4. N-5751M2 Solvent-based moisture cure 90% Zn
5. Intershield 300V Aluminum-rich epoxy
6. Epoxzen Organic epoxy with 90% Zn
Rust converters:
1. Gempler’s (water-based, tannic acid)
2. Loctite rust treatment (polymeric-based, barium sulfate)
3. Total Solutions (water-based, tannic acid)
4. Phoscote (phosphoric acid – current USMC product) <>>
5. VpCI CorrVerter (combined rust converter and primer)
6. Corroseal (water-based, tannic acid with primer)
7. Gem Rust Killer (under test)
The rust converters were coated with a non-corrosion inhibiting epoxy primer and a polyurethane topcoat. While they are good paints, there was no chance that the rust converters would look good in these tests. It is unfortunate that they didn't compare to a sample without a converter. All I can say is that none of the rust converters looks bad, since all they do is help the paint stick to the metal.Last edited by MN Dave; 04-16-2018, 11:52 AM.Comment
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Re: Steel CB protection
I wonder if you could design a steel centerboard with a protective zinc?I will beg you for advice, your reply will be concise, and I will listen very nicely and then go out and do exactly what I want! (Apologies to Lerner and Lowe.)Comment
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Re: Steel CB protection
As to you question about designing a cb with a protective zinc, That is what we have been recommending - hot dipped.It really is quite difficult to build an ugly wooden boat.
The power of the web: Anyone can post anything on the web
The weakness of the web: Anyone can post anything on the web.Comment
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Re: Steel CB protection
Don't forget the zinc anodes or impressed current systems on those thousands of ships:
This links to a pdf that has the results of testing done on zinc rich primers, followed by tests on rust converters.
Zinc rich paints:
1. Zinga Organic epoxy primer 96% Zn
2. Zinc Clad IV Solvent-based 85% Zn
3. Zinc Clad XI Water-based inorganic Zn silicate with no VOC and 90% Zn
4. N-5751M2 Solvent-based moisture cure 90% Zn
5. Intershield 300V Aluminum-rich epoxy
6. Epoxzen Organic epoxy with 90% Zn
Rust converters:
1. Gempler’s (water-based, tannic acid)
2. Loctite rust treatment (polymeric-based, barium sulfate)
3. Total Solutions (water-based, tannic acid)
4. Phoscote (phosphoric acid – current USMC product) <>>
5. VpCI CorrVerter (combined rust converter and primer)
6. Corroseal (water-based, tannic acid with primer)
7. Gem Rust Killer (under test)
The rust converters were coated with a non-corrosion inhibiting epoxy primer and a polyurethane topcoat. While they are good paints, there was no chance that the rust converters would look good in these tests. It is unfortunate that they didn't compare to a sample without a converter. All I can say is that none of the rust converters looks bad, since all they do is help the paint stick to the metal.
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Re: Steel CB protection
Wow! somebody tried to read one of my links! Sorry, it was a bit obtuse. Unfortunately, that wasn't as clearly written as it could have been, but wasn't much worse than the better articles. Welcome to my world. One thing about corrosion testing to remember is that corrosion tests are like an old army mule, they don't reproduce very well.
Might be time to remove the skegs, get them thoroughly sand blasted and hot dipped by the sounds of it. But next best is probably sand blast in place and a zinc rich primer. I don't know what sticks to stainless though.
As for what sticks to stainless steel, based on my observations of my stainless frying pan, eggs stick really well, followed by just about everything else, except paint.
Stainless needs to be really clean. it will help to lightly grit blast with a fine clean aluminum oxide grit that has never been used on steel. It also helps to clean with something like Alumaprep 33, which is pretty much Ospho with some degreaser. If your water is hard or high solids, rinse with RO or distilled water.
Do not galvanize or use cold galvanizing on stainless. The corrosion prof at MIT explained the effect on corrosion potentials to me and the part that I understood was that it it's bad to galvanize stainless. The details -- arrgh.
There are primers recommended for stainless that are also good for galvanized surfaces. Etching primers are good. I hate to recommend a chromate primer, but Pettit 6455 is good (apply thin, if you can't see through it, the paint will peel.) It is a version of the old DOD-P-15328 polyvinyl butyrate. I would also recommend an easier to use, less hazardous primer like Pettit 6980 Rustlok. The reason to paint stainless not to protect the stainless, it is to protect the other metals nearby. Painting stainless will reduce the large exposed area of cathode that causes galvanic corrosion of everything else.
Surprisingly, aluminum anodes are often no more costly than zinc ones. Also, because most are cadmium-free, aluminum anodes are less of a hazard to the marine environment. So, regardless of what a diver, boatyard manager or other industry pro tells you, there are several advantages, and no drawbacks, to switching to aluminum anodes.Comment
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Re: Steel CB protection
What he said... always galvanize if you can. No coating can approach the durability. It is self healing if scratched. Generally, hot dip galvanizing is charged by the weight of the material being dipped and spun. Our local high school Metalworking program build's park benches and has them galvanized, then powder coated. Some of my volunteer work with the kids as rewarded with an offer to allow me to throw some parts into the basket I had fabricated for a quick release bowsprit mechanism. It otherwise would have cost me about $50.Comment
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Re: Steel CB protection
Steel Centerboards.... a comment was made on how to fair the board to give it a lifting profile. I had a piece of 5/8" boiler plate my dad pulled from the scrap bin at work and gave me when I was building a sailing dory. I machined the edges square, then made some hardwood leading and trailing edges. I drilled and tapped the front and read edges of the boiler plate and after painting (I was in high school, so did not know about galvanizing) and simply attached the fairings to get a little better efficiency. NACA lifting foils are the ultimate solution, but the shape is impractical for a centerboard in terms of width and they have not flat surfaces to bear against a centerboard trunk.
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Re: Steel CB protection
JayComment
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