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Epoxying my ferro hull

ferro epoxy

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#11 Seasick sheamus

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Posted 18 November 2015 - 05:15 PM

what about polyester resin? would that be suitable as a barrier coat?


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#12 Seasick sheamus

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Posted 18 November 2015 - 06:41 PM

can I get a copy of your colin brooks CD book? I'd gladly paypal you some cash to cover costs?


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#13 wheels

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Posted 19 November 2015 - 06:00 AM

what about polyester resin? would that be suitable as a barrier coat?

No, Polyester, due to the way it hardens (the way the molecules link to make it a solid) creates a very brittle and easily cracked coating, along with it not being very good at adhering to anything other than itself. So epoxy is by far the better to use as it adheres well and is slightly flexible and thus will not crack.


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#14 wheels

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Posted 19 November 2015 - 06:30 AM

 

Now you're just making sh*t up. Read the quote from Brookes again

Certainly not intentionally. I will indeed read it again, but I do very much remember reading his comments about the affects of a FC hull due to the Magnetic fields in the Steel core affecting the swing of a compass.

But re AF, I have been in this game a very very long time. I have had training from International/Epiglass. But if you want other proof, read the following.
This first one is from Rustoleum, the makers of the Epoxy/Copper Coating. They suggest that you can coat this directly onto bare steel, No other pre coatings of anything reguired.
http://www.rustoleum...oulingPaint.pdf
Choose any Anti-fouling manufacturer and read their specs and you will find that they happy to have their copper based AF's painted onto any material other than Aluminium. Hempels say that theirs can be used on Aluminium as long as their barrier coat system is applied first.
 


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#15 haiqu

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Posted 19 November 2015 - 12:07 PM

can I get a copy of your colin brooks CD book? I'd gladly paypal you some cash to cover costs?

 

The actual books are available here:

 

http://www.hartley-b....com/books.html

 

Doesn't look like they sell the CD any longer. I can't send it from here, I'm on a G4 modem and bandwidth costs me heaps.


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#16 haiqu

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Posted 19 November 2015 - 12:20 PM

Certainly not intentionally. I will indeed read it again, but I do very much remember reading his comments about the affects of a FC hull due to the Magnetic fields in the Steel core affecting the swing of a compass.

But re AF, I have been in this game a very very long time. I have had training from International/Epiglass. But if you want other proof, read the following.
This first one is from Rustoleum, the makers of the Epoxy/Copper Coating. They suggest that you can coat this directly onto bare steel, No other pre coatings of anything reguired.
http://www.rustoleum...oulingPaint.pdf
Choose any Anti-fouling manufacturer and read their specs and you will find that they happy to have their copper based AF's painted onto any material other than Aluminium. Hempels say that theirs can be used on Aluminium as long as their barrier coat system is applied first.
 

 

Don't care who trained you or what Rustoleum says, you (and Rustoleum) clearly don't understand galvanic reaction. For harsh environments such as salt water a 0.15V difference in Anodic Index is acceptable. The difference between copper and steel is 0.5V and between copper and aluminium is 0.55V so in each case what you have is a battery that eats one of the poles away.

 

I learned this stuff in basic metallurgy 40 years ago.

 

http://www.engineers...apatability.htm

 

And that's also why you don't use brass-plated hinges from the hardware store on a yacht. They'll rust out in 3 months.


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#17 Island Time

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Posted 19 November 2015 - 01:43 PM

I'm not expert at this by any means, but haiqu, would that not be if the products are joined by seawater? If it's an epoxied ferro hull, there is (should be) a waterproof barrier, and therefore no issue unless the hull is damaged and the barrier breached.

Copper coat, by it's nature is copper suspended in epoxy. I guess they have tested this??


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#18 wheels

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Posted 19 November 2015 - 03:56 PM

Don't care who trained you or what Rustoleum says, you (and Rustoleum) clearly don't understand galvanic reaction. For harsh environments such as salt water a 0.15V difference in Anodic Index is acceptable. The difference between copper and steel is 0.5V and between copper and aluminium is 0.55V so in each case what you have is a battery that eats one of the poles away.

 

I learned this stuff in basic metallurgy 40 years ago.

 

http://www.engineers...apatability.htm

 

And that's also why you don't use brass-plated hinges from the hardware store on a yacht. They'll rust out in 3 months.

I don't wish to argue with you, but you are only part way there.
Before I go into greater detail as to how it works, I can very simply explain in this simple example. When you fit the Zinc Anode to your Hull, do you connect it directly to metal? What would the Anode do if it were insulated from the Hull or Metal it was there to protect?
Actually it would do nothing. It would not erode away. One of the sayings with FC is that if you did not have the Prop and shaft in the water, you would not need an anode at all. There is nothing to protect. The Steel is insulated and isolated from the water by the plaster.
So OK, for the anode to work, it must be connected to any metal that is in the water, so as to protect it.
Righty...so for dissimilar Metals in Seawater, we basically have a battery. If you think of a Car battery for a moment, for a current to flow, you must connect something conductive between the positive(anode) and Negative(cathode). If you do not have a connection, then current can not flow. But also, of you tip the acid out, there is no connection between the plates for the current to flow through and the battery will not produce power either. The name Circuit is related to Circle. For a current to flow, you have to have a connection between the different metals as well as the circuit connected between them.
If we isolate the metals, we no longer have a circuit. We can isolate either via some non conductive material, or in the case of our metals in Seawater, we can isolate by keeping the seawater out between the two of them. That is done by the epoxy barrier coat going in between the Steel and the Copper.
So on our FC Hull, the Plaster will actually be just fine at insulating the Steel from the Water and copper. But to add to that, many apply an Epoxy as well.
Going back to the Hartley/Brooks book, they also state that it is quite unnecessary to epoxy the Hull. Although many do, they state it is really a waste of money. However, if it is part of a two pot paint system, then there is also no harm in epoxying it either.


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#19 haiqu

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Posted 19 November 2015 - 06:12 PM

I'm not expert at this by any means, but haiqu, would that not be if the products are joined by seawater? If it's an epoxied ferro hull, there is (should be) a waterproof barrier, and therefore no issue unless the hull is damaged and the barrier breached.

Copper coat, by it's nature is copper suspended in epoxy. I guess they have tested this??

 

Do a read around some of the other forums and find out about the many people who have had problems with copper based antifoul "disappearing" within months of application.

 

Assuming the hull is epoxied (and many are not) then the effect will be reduced. But it only takes one salt water contact with the armature through a fissure in the cement or a crack or chip and voila! we have a battery.


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#20 haiqu

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Posted 19 November 2015 - 06:16 PM

The name Circuit is related to Circle. For a current to flow, you have to have a connection between the different metals as well as the circuit connected between them.

 

Dunno who this is aimed at. I'm a retired electronics engineer, I'm pretty sure I know how electricity works by now. 8^]


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