Copper Keel cooler, should it be painted?

[jnrhacksaw]

I'm in the process of restoring a 1940's steel cruiser, at some point the boat has been fitted with keel coolers made from copper pipe.

 

Should these be painted? I presume bare copper might interfere with the zinc anodes fitted.

Edited January 3, 2016 by jnrhacksaw

[Chewbacka]

Of the three metals - Zinc, steel and copper - the copper is the most noble so will be 'protected' by both the zinc and steel. Is the copper pipe electrically connected connected - by touch for example - to the steel hull? Is there any corrosion of the hull close to the copper pipes?

My worry would not be the anodes (Zn or Mg?) but the steel hull close to the copper pipes, also if there is corrosion it may creep under the hull paint and be a bit less visible.

 

You also said Zinc anodes which are used in salty water in which case I would be concerned as salt water is very good for corrosion.

It is not clear if your copper pipes are a heat exchanger in a 'box' or pipes that pass through the hull and are cooled by the water.

 

So a few more details may help you get better answers.

[jnrhacksaw]

The coolers consist of copper pipes that run through the hull and then run along the outside next to the keel.

 

The copper should be isolated from the hull where they pass through by several thick coats of epoxy and silkalfex, the mounting brackets are isolated with PVC packings.

 

There where signs of corrosion near the copper pipes on the hull when I stripped the boat back to bare steel.

 

I guess the best way to go would be to epoxy the pipes therefore insulating them from any electrolytic or galvanic action?

 

I'm not sure which metal the anodes are, I'll try some fillings with the blow torch to see. When I bought the boat these where painted over

[Tony Dunkley]

I'm in the process of restoring a 1940's steel cruiser, at some point the boat has been fitted with keel coolers made from copper pipe.

 

Should these be painted? I presume bare copper might interfere with the zinc anodes fitted.

 

The answer to the question about painting the keel cooling pipes is that they should not be painted, but there are some other things to think about as well :~

 

* Are the keel cooling pipes going to continue to be used, or are you installing Heat Exchanger cooling ?

 

* Is the pipework, and the through hull fittings, intentionally and reliably, insulated electrically from the hull itself ?

 

* Is the external pipework of sufficient surface area for any engine which may be installed in the foreseeable future ?

 

* Will you be keeping/using the boat in fresh or salt water ?

[jnrhacksaw]

Tony,

 

Yes the pipes are still being used,

 

I'm not convinced that even 5 coats of epoxy and silkflex is sufficient to electrically insulate the bronze through-hull from the hull, however I'll try a meter to see if it has at least been successful for the short time they have been fitted. Maybe I should consider a plastic through hull connection or a metal one shrouded in something non conductive?

 

judging by what you and Chewbaka have said it seems isolating the pipes from the hull is the most important aspect, I presume you warn against painting them as this affects the cooling ability?

 

the boat will be used in fresh water at first and then moved to salt water.

[cuthound]

Tony,

 

Yes the pipes are still being used,

 

I'm not convinced that even 5 coats of epoxy and silkflex is sufficient to electrically insulate the bronze through-hull from the hull, however I'll try a meter to see if it has at least been successful for the short time they have been fitted.

Well 1 coat of epoxy is enough for 11kV high voltage transformers, so it should be enough to combat the volt or two needed to cause galvanic corrosion.

[Chewbacka]

The other option is to talk to a boat yard/marine engineer to see if it would be better to replace with galvanised steel pipe. But it is the salty water aspects that would concern me the most.

 

Also it is important to ensure the coolant is good, to prevent corrosion between the engine block - which I assume is iron based - and the copper pipes.

I seem to remember being told that the red stuff is no good for a copper/iron system and you need to use the blue stuff. Worth checking with the coolant supplier tech line.

[Murflynn]

agree with Chewbacka.

 

fitting copper tubes to steel hulls is simply bad practice, they should be replaced with steel or galvanised steel.

[swift1894]

I've often wondered about the reaction between steel hulls and bronze inlet/outlet fittings under water, on very old boats. Will the steel eventually corrode?

[Bee]

This type of system is quite common but I have never seen copper used before. If it was mine I would swap the copper and use steel, plenty of plumbing fittings available in malleable iron or some sort of ferrous stuff, welded to the hull would get rid of potential leaks from the copper thru' hull fittings as well.

I've often wondered about the reaction between steel hulls and bronze inlet/outlet fittings under water, on very old boats. Will the steel eventually corrode?

Probably, that's why there are lots of anodes on big ships near the propeller and in the bowthruster tube. I have an anode adjacent to a bronze underwater fitting on my boat. I am not convinced about the need for anodes on a well painted hull but if there is copper / bronze / brass /gold anywhere then I bung an anode on.

[Chewbacka]

............. I am not convinced about the need for anodes on a well painted hull but if there is copper / bronze / brass /gold anywhere then I bung an anode on.

Not a lot of gold skin fittings on my boat, though if somebody were to give me a 3kg gold anode I would be very happy even though it would do nothing to stop corrosion.

[Sjpbikes]

How did u get on with this ?

Was it copper or bronze ?

Sorry to restart the thread but am thimking of making a keel cooler from copper then dipong in resin to protect ? Would this be ok tho i understand that id loose sum heat trasfer but was going to go oversized anyway !

This will be gitter to a grp hull so would i need anodes ?

[Sjpbikes]

How did u get on with this ?

Was it copper or bronze ?

Sorry to restart the thread but am thimking of making a keel cooler from copper then dipong in resin to protect ? Would this be ok tho i understand that id loose sum heat trasfer but was going to go oversized anyway !

This will be gitter to a grp hull so would i need anodes ?