Copper plating propeller

[BabaYaga]

Definitely. The only slight drawback is that painting the prop reduces cathode area and saves anodes. But overall it is well worth doing.

It might be worth pointing out that, according to the theory, to get a good anti fouling outcome from copper plating, there should be no zinc anode used.
I would not claim to fully follow the reasoning, but my understanding is that the presence of a zinc anode (in contact with the prop) will prevent or slow down the release of copper ions from the plating, which is what discourages the barnacles from settling.

 

[thinwater]

It might be worth pointing out that, according to the theory, to get a good anti fouling outcome from copper plating, there should be no zinc anode used.
I would not claim to fully follow the reasoning, but my understanding is that the presence of a zinc anode (in contact with the prop) will prevent or slow down the release of copper ions from the plating, which is what discourages the barnacles from settling.

^^ This. I've tested this.

It turns out there is a minimum required leaching rate. Bare copper and 2-year paints are in the same range. Copper AC coils that are protected with anodes can foul.

 

[howardclark]

S

^^ This. I've tested this.

It turns out there is a minimum required leaching rate. Bare copper and 2-year paints are in the same range. Copper AC coils that are protected with anodes can foul.

dont quite understand - does that mean we could leave the anode as is if we plate the prop?

 

[vyv_cox]

It might be worth pointing out that, according to the theory, to get a good anti fouling outcome from copper plating, there should be no zinc anode used.
I would not claim to fully follow the reasoning, but my understanding is that the presence of a zinc anode (in contact with the prop) will prevent or slow down the release of copper ions from the plating, which is what discourages the barnacles from settling.

The boat on which I plated the prop had no anodes.

 

[Poey50]

I would love to get this done but my Darglow Featherstream has stainless blades.

 

[thinwater]

S

don't quite understand - does that mean we could leave the anode as is if we plate the prop?

No. If there is an anode next to the prop, the release of Cu ions is suppressed and the prop will foul. Since only 5-10 microns per year is lost corrosion (plus mechanical wear--maybe 5-10 times that on the leading edge or surfaces that cavitate) it should last a few years any way, though protection from dezinc will only last as long as the coating is reasonably well intact.

For comparison, copper pipe is about 1000 microns thick.

 

[thinwater]

Searching the net, I see lots of claims Cu plating does not work ... but none of them removed the zinc. With the zinc in place, obviously, it won't work much better than a bronze prop, and we can't leave the zinc off of an un-plated prop because of de-zinc. But if the prop is fully coated in Cu, how can it dezinc?

• Have we seen any evidence of dezinc? There seems to be some where the plating wore away from the leading edge of Baba Yaga's prop. Yvy did not expereince mechnical wear as reported in his write-up, because the boat was little used.
• Is there a a galvanic reaction between the bronze and the zinc when the interface is exposed to seawater? This may have accelerated the flaking Baba Yaga experienced.

I do NOT know these things. This is for discussion. Vyv, have you piled many miles on the prop since?

It seems tot obvious not to be widespread practice.

 

[vyv_cox]

Searching the net, I see lots of claims Cu plating does not work ... but none of them removed the zinc. With the zinc in place, obviously, it won't work much better than a bronze prop, and we can't leave the zinc off of an un-plated prop because of de-zinc. But if the prop is fully coated in Cu, how can it dezinc?

• Have we seen any evidence of dezinc? There seems to be some where the plating wore away from the leading edge of Baba Yaga's prop. Yvy did not expereince mechnical wear as reported in his write-up, because the boat was little used.
• Is there a a galvanic reaction between the bronze and the zinc when the interface is exposed to seawater? This may have accelerated the flaking Baba Yaga experienced.

I do NOT know these things. This is for discussion. Vyv, have you piled many miles on the prop since?

It seems tot obvious not to be widespread practice.

No, we sold the boat almost immediately afterwards. The acid copper process used was chosen to give the hardest finish but when we inspected it the total mileage was low, maybe 100.

 

[BabaYaga]

Searching the net, I see lots of claims Cu plating does not work ... but none of them removed the zinc. With the zinc in place, obviously, it won't work much better than a bronze prop, and we can't leave the zinc off of an un-plated prop because of de-zinc. But if the prop is fully coated in Cu, how can it dezinc?

• Have we seen any evidence of dezinc? There seems to be some where the plating wore away from the leading edge of Baba Yaga's prop. Yvy did not expereince mechnical wear as reported in his write-up, because the boat was little used.
• Is there a a galvanic reaction between the bronze and the zinc when the interface is exposed to seawater? This may have accelerated the flaking Baba Yaga experienced.

I do NOT know these things. This is for discussion. Vyv, have you piled many miles on the prop since?

It seems tot obvious not to be widespread practice.

With a nickel-aluminium bronze propeller, such as mine, there will be no dezincification (as there is no zinc in the composition), but still some corrosion, pitting etc from galvanic action due to dissimilar metals cannot be completely ruled out. After all, feathering propellers of this type all seem to come with dedicated zinc anodes. On the other hand, what I learned from the thread in January (linked in post #1) was that this type of bronze alloy should be pretty resistant.
A brass propeller is perhaps more 'in need' of the protection of a zinc anode and therefor copper plating and skipping the anode would mean taking a greater risk – I don't know.
Another aspect is that the stern gear is often used as a path to ground for AC and/or DC – which I guess could also be a good reason for protection by a zinc anode on the prop.
Whereas my shaft and prop are insulated from the electrics.

 

[arcot]

So has anyone tried coppercoat on a prop?

 

[vyv_cox]

So has anyone tried coppercoat on a prop?

Yes but at the time I had not discovered the need for an etch primer. It fell off very quickly. I suppose that it might work on top of Hammerite Special Metals.