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Bill3558
Joined: 12 Jan 2007
Posts: 121
City/Region: RIchmond Hill, Georgia
State or Province: GA
C-Dory Year: 2006
C-Dory Model: 22 Cruiser
Vessel Name: Pluto
Photos: Pluto
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 Posted: Fri Mar 30, 2007 9:03 am Post subject: Trim Tab Anti-Fouling?? |
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Do I need to put some kind of antifouling coating on my stainless trim tabs? Boat will stay in the water during the summer and we have heavy growth when the water warms up. I have done the bottom with sealer and paint but havent touched the tabs.
I went to Boaters World yesteday to get some kind of metal primer and the guy said antifouling on stainless wasnt needed!
Thanks for any info. |
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JamesTXSD
Joined: 01 Mar 2005
Posts: 7481
City/Region: from island boy to desert dweller
State or Province: AZ
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: "Wild Blue" (sold 9/14)
Photos: Wild Blue
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| Posted: Fri Mar 30, 2007 9:15 am Post subject: |
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It may be a factor of your local water, but we did paint our trim tabs. Yes, it looks kinda funky, but they were definitely getting barnacles and slime after just a few weeks in our local (high salinity) water.
As a side note, there is a CLEAR antifouling paint made just for lower units, trim tabs, etc. It does not last as long as regular bottom paint (you'd have to redo the tabs every 6 months or so), but it wouldn't be a big deal. Several different manufacturers make this stuff, including one who makes it in a spray can.
HTH
Best wishes,
Jim B.
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Jim & Joan
CD-25 "Wild Blue" (sold August 2014)
http://captnjim.blogspot.com/
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Papillon
Joined: 31 Mar 2005
Posts: 949
City/Region: DeBary, Fl. *On the St. John's River*
State or Province: FL
C-Dory Year: 1993
C-Dory Model: 22 Angler
Vessel Name: Papillon
Photos: Papillon
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| Posted: Fri Mar 30, 2007 9:49 am Post subject: |
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In some waters you do need antifouling paint on everything below the waterline. SW Florida is one such place. Do not use the same bottom paint you have on the hull on any metal items , the coppers in the paint will turn those items into a battery. Not Good.
They make special paints for lower units and trim tabs so just keep looking and do it right the first time.....It's always cheaper in the long run.
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Mike Taylor
330-936-1030
1993 Angler-02' 115 Suzuki 4 Stroke |
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Doryman
Joined: 03 Oct 2006
Posts: 3807
City/Region: Anacortes
State or Province: WA
C-Dory Year: 2006
C-Dory Model: 255 Tomcat
Vessel Name: Lori Ann
Photos: Lori Ann
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| Posted: Fri Mar 30, 2007 12:09 pm Post subject: |
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The folks at LaConner Marintime are experimenting with a clear ceramic coating for outboard engine lower units, etc. They put some on my Yamaha 150s and so far it seems to be working well. The crud attaches to the treated part while at rest but sloughs off once you get going. I don't have a brand name for the coating but you can call LaConner Maritime at 360-466-3629 for more information.
Warren
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Doryman
M/V Lori Ann
TomCat 255, Hull #55, 150 Yamahas
Anacortes, WA
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Sea Wolf
Joined: 01 Nov 2003
Posts: 8650
City/Region: Redding
State or Province: CA
C-Dory Year: 1987
C-Dory Model: 22 Cruiser
Vessel Name: Sea Wolf
Photos: Sea Wolf
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| Posted: Fri Mar 30, 2007 2:14 pm Post subject: |
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| Papillon wrote: | In some waters you do need antifouling paint on everything below the waterline. SW Florida is one such place. Do not use the same bottom paint you have on the hull on any metal items , the coppers in the paint will turn those items into a battery. Not Good.
They make special paints for lower units and trim tabs so just keep looking and do it right the first time.....It's always cheaper in the long run. |
This is absolutely correct!
My Bennet Trim tabs are painted with Pettit Trinidad anti-fouling paint which is 75% copper. However, tabs are stainless, and the paint and copper don't seem to be a problem on them.
I'll illustrate the problem of anti-fouling paint on aluminum alloy by telling you that the shop that painted my Sea Ray's bottom also painted up to the edge of the outdrives, resulting in a lot of corrosion. Here's what happened:
The Mercruiser outdrives have a galvanic protection system on them called the Mercathode System. It electronically senses the galvanic potential between the outdrives and the water, then applies enough voltage to the outdrives to neutralize the corrosion potential. Pretty neat in principle and normal operation!
But when you paint the outdrive (aluminum) with paint containing metal, or even have your metal containing bottom paint touching the outrives, a battery like galvanic cell is created, charging both the outdrives and the metallic painted hull electrically.
This charge makes it impossible for the Mercathode unit to sense the corrosion potential accurately, and the galvanic cell (battery) created between the hull and the outdrive causes the metal on each of them to become corroded.
Painting the outdrive or leg of an outboard creates a similar galvanic cell with the associated corroson with or without the help of a corrosion control system.
This is just a specific example of the general principle that any time two different metals are bonded together, a galvanic (battery) cell is created and the potential for corrosion exists. Putting this newly created battery cell into water, especially salt water (an electrolyte), enables the two metals to freely go ahead and corrode at full maximum speed.
Metals corrode because they conduct electricity and are chemically active (except for gold, platinum, etc.)
Each metal has a different level of, or potential for, chemical activity.
When two are touching each other, they both are trying to chemically react, and one will be stronger than the other.
Add either water, oxygen, salt, acids, or bases, and they can freely react with each other (and whatever else is around) to chemically change, which we call corrosion. . Electrons are exchanged in the process, and if the metals are connected with wires, a current will often flow, making a battery.
Some alloys, like stainless steel, have mixtures of metals in them so that the atoms tie each other up, and the potential cor corrosion is greatly reduced.
Whenever you're planing a project, think about the potential for corrosion between different metals, especially if it will be exposed to water, and salt water in particular.
Joe.
_________________
Sea Wolf, C-Brat #31
Lake Shasta, California
  
"Most of my money I spent on boats and women. The rest I squandered'. " -Annonymous |
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Doryman
Joined: 03 Oct 2006
Posts: 3807
City/Region: Anacortes
State or Province: WA
C-Dory Year: 2006
C-Dory Model: 255 Tomcat
Vessel Name: Lori Ann
Photos: Lori Ann
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| Posted: Fri Mar 30, 2007 2:50 pm Post subject: |
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Joe, thanks for bringing up the galvanic corrosion issue. I had concerns about this as well and the LaConner Maritime people addressed them by making sure that my sacrificial anodes were not painted, nor were the contacts.
Warren |
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CHardy
Joined: 17 Oct 2006
Posts: 20
City/Region: occoquan
State or Province: VA
C-Dory Year: 2006
C-Dory Model: 22 Cruiser
Vessel Name: C Hardy
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| Posted: Fri Mar 30, 2007 3:14 pm Post subject: |
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brass keel strip was painted over with bottom paint...I am going to remove the paint from it...has any one had problems with it?
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Bill3558
Joined: 12 Jan 2007
Posts: 121
City/Region: RIchmond Hill, Georgia
State or Province: GA
C-Dory Year: 2006
C-Dory Model: 22 Cruiser
Vessel Name: Pluto
Photos: Pluto
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| Posted: Fri Mar 30, 2007 4:13 pm Post subject: |
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Thanks for all the good information. I dont think Mr. Boaters World was up to speed on this one.
I too painted the brass bow insert with copper anti fouling paint. Any issue there do you think? |
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