Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 09-03-2016, 04:14   #1
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,744
Effect of Prop Antifouling on Prop Anode Wear?

Most people around here polish their props and leave them as bare metal. And I also do that. For some reason, the prop doesn't foul all that much.

But my prop anodes wear intensely, and are gone in 4 months, which is the limiting factor for me for a lift out.

For some reason, having a shaft anode on doesn't seem to make a lot of difference. I don't understand that.

I wonder if I were to paint my prop with antifoul, whether that would slow down anode wear by reducing contact with sea water?

Anyone have any experience?
__________________

__________________
"Parce que je suis heureux en mer, et peut-Ítre pour sauver mon ame. . . "
Dockhead is offline   Reply With Quote
Old 09-03-2016, 05:18   #2
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Albany Ga.
Boat: Island Packet 38
Posts: 17,045
Re: Effect of Prop Antifouling on Prop Anode Wear?

Yes,
You have an Autoprop right?
You need to get the adapter for it that allows a regular anode be put on it, regular anode has at least twice as much metal as the Autoprop one so it lasts longer and is much more available. I had to cut a little off my shaft to fit it though
Autoprop Anode Adapter | Islers Diving

Fsstbttms showed it to me in an earlier thread, I apologize if I misspelled your name.

Once I get the prop cleaned off well, buffed with a green pad, I apply this
LanoCote Prop & Bottom
Seems to help with growth, growth still happens, just it's a whole lot easier to get it off though.

Oh and my shaft anode doesn't wear nearly as fast as the prop one either, which makes me think the prop anode is very important on an Autoprop.


On edit, maybe prop speed might help electrically insulate a prop, I don't know.
Next time I haul for a bottom job I'm thinking of removing the prop and applying it.
You really haul for zincs? I know the water is cold, this is the dry suit I cave dive with, it is an excellent, but budget priced dry suit, since it is crushed neoprene and fits really well, not like a bag, it swims like a wet suit.
http://www.pinnacleaquatics.com/black-ice/
__________________

__________________
a64pilot is offline   Reply With Quote
Old 09-03-2016, 14:36   #3
Registered User
 
Hydra's Avatar

Join Date: May 2009
Location: Lorient, Brittany, France
Boat: Gib'Sea 302, 30' - Hydra
Posts: 1,229
Re: Effect of Prop Antifouling on Prop Anode Wear?

Yes, I paint my propeller (Nautix primer + antifouling) and the hub anode lasts a few years. However, the paint doesn't last one year: I suspect it is eroded by cavitation.

Alain
__________________
Hydra is offline   Reply With Quote
Old 09-03-2016, 14:51   #4
cruiser

Join Date: Oct 2015
Posts: 285
Re: Effect of Prop Antifouling on Prop Anode Wear?

I have a theory that friction as the prop is spinning/dragging water across it has to do with accelerated anode wear. My collar anodes wear far faster than the anodes on the drive. That said, 4 mo. seems a bit fast



I've painted my props this last haul with the barnacle barrier zinc stuff, but it hasn't been long enough to see whether there is any change
__________________
AD28 is offline   Reply With Quote
Old 10-03-2016, 08:35   #5
Registered User
 
Rustic Charm's Avatar

Join Date: Jun 2011
Location: Tasmania, Australia
Boat: Bieroc 36 foot Ketch
Posts: 4,898
Re: Effect of Prop Antifouling on Prop Anode Wear?

I dont think this will help much, but i, like most people down here paint their props. Im not familiar with anyone who polishes props. I use a hard, thats a non ablative anti foul on the prop. My shaft anode lasts about two season's, or two years. It could possibly last three but after two its worn enough for me not to take the chance.

If your using anodes in that sort of speed is it not reasonable to conclude you may have a power leak?
__________________
Rustic Charm is offline   Reply With Quote
Old 10-03-2016, 08:46   #6
Registered User

Join Date: Oct 2011
Location: Sequim, WA
Boat: Pacific Seacraft Dana 24
Posts: 165
Re: Effect of Prop Antifouling on Prop Anode Wear?

Sounds like a galvanic isolator would be a good application here plus a thorough check of your electrical system. 4 mo. Indicates something amiss to me.
__________________
Xthewater is offline   Reply With Quote
Old 10-03-2016, 08:49   #7
Registered User
 
leftbrainstuff's Avatar

Join Date: May 2011
Location: San Francisco and Australia
Boat: Liberty 458
Posts: 1,978
Re: Effect of Prop Antifouling on Prop Anode Wear?

Anode 101

NOTE Anode depletion is a good thing. Anodes lasting too long in salt water is cause for alarm.

Conductivity of the medium and anode cathode delta on the galvanic scale are the primary factors affecting corrosion rate.

Secondary factors include surface area, volume and anode mounting.

Polishing cathodes (items protected) will help to minimise pitting corrosion and make it more difficult for growth to adhere. It wont impact anode depletion rates. Not in a measurable way to be precise.

In practice anode depletion rate is accelerated in warm and polluted salt water. Pollution includes anything in solution that increases conductivity.

Ways to deal with accelerated anode depletion include:

1) larger volume anode
2) impressed current protection. Essentially you are adding another less noble anode
3) accept the corrosion rate and change anodes often
4) move the boat to a less conductive medium. Fresh water or less polluted medium.

We have a maxprop. The anode depletes in 3 to 4 months. Our frigoboat zincs and 6x4 rudder zinc deplete much more slowly and are replaced annually.

The maxprop anode is hydrodynamically efficient but has too small a surface area around the 3 mounting screws. We paint the spotfaced holes in the zinc with nail polish to slow erosion around the mounting bolts. This eliminates the potential for the anode to fall off. Depletion now occurs on the anode free surface. NOTE Do not paint the anode or anode mounting surface.

The anodes are all doing there job and protecting the ss and bronze cathodes. We have our diver change the maxprop zinc each quarter. To avoid such frequent anode replacement we could use an impressed current system like a salty dog.

I would recommend you conduct a corrosion survey on your vessel first. This will identify if you have a bonding issue. Next I would check my neighbours boats to see if they have an issue. Your anodes might be part of a multi boat circuit. Finally you could use an impressed current solution.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app
__________________
leftbrainstuff is offline   Reply With Quote
Old 10-03-2016, 08:58   #8
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Albany Ga.
Boat: Island Packet 38
Posts: 17,045
Re: Effect of Prop Antifouling on Prop Anode Wear?

The Autoprop anode is sort of undersized and if you don't apply something to insulate it where it attaches to the prop it wears fast there as its thin, there isn't a whole lot of metal on the anode.
But curiously the prop anode does wear at a much higher rate than the shaft collar anode does even though they are of course electrically connected. I'm just guessing, but I'd guess that SS isn't that great a conductor and the metal of the Autoprop isn't as Noble as the SS shaft?
I get about 6 months or maybe 9 out of a "B" size prop anode that the Isler diving adapter lets me use, I got maybe 4 months out of the stock anode myself, but I do change them early, I don't let them wear til they fall off.

I got about the same life as Dockhead, so unless we both have current leaks, I think his wear rate isn't excessive
__________________
a64pilot is offline   Reply With Quote
Old 10-03-2016, 09:02   #9
Registered User
 
duefocena's Avatar

Join Date: Aug 2010
Location: Newport Beach, CA.
Boat: TPI Lagoon Catamaran 42'
Posts: 234
Images: 1
Re: Effect of Prop Antifouling on Prop Anode Wear?

Would painting the prop foil the contact between the zinc and the prop? I have H-5 Autoprops and go through my prop anodes every 6-9 months or so. The shaft zincs last about 3-4 months and I've added a galvanic isolator as well as a " Billy Bass" ( clip on 1 kilo zinc ). Attributing the galvanic action to old docks with a lot of electrical leaks I replace them regularly rather than risk the props. When I found they were wearing mostly at the screw holes, I painted the holes and corners leaving the base clean to make contact. This made them last twice as long.
__________________
duefocena is offline   Reply With Quote
Old 10-03-2016, 09:03   #10
Registered User

Join Date: Jun 2015
Location: Houston
Boat: Beneteau Cyclades 51.4
Posts: 213
Images: 1
Re: Effect of Prop Antifouling on Prop Anode Wear?

Quote:
Originally Posted by leftbrainstuff View Post
Anode 101

Conductivity of the medium and anode cathode delta on the galvanic scale are the primary factors affecting corrosion rate.

Secondary factors include surface area, volume and anode mounting.

Polishing cathodes (items protected) will help to minimise pitting corrosion and make it more difficult for growth to adhere. It wont impact anode depletion rates. Not in a measurable way to be precise.

In practice anode depletion rate is accelerated in warm and polluted salt water. Pollution includes anything in solution that increases conductivity.

Ways to deal with accelerated anode depletion include:

1) larger volume anode
2) impressed current protection. Essentially you are adding another less noble anode
3) accept the corrosion rate and change anodes often
4) move the boat toba less conductive medium. Fresh water or less polluted medium.

We have a maxprop. The anode depletes in 3 to 4 months. Our frigoboat zincs and 6x4 rudder zinc deplete much more slowly and are replaced annually.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app
I once put the voltmeter in the water next to a neighbor's boat and I got 4.6 volts DC. He also was melting his zincs every month. I also moved my boat to another dock and saved my anodes.
__________________
sailon46 is offline   Reply With Quote
Old 10-03-2016, 09:12   #11
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Albany Ga.
Boat: Island Packet 38
Posts: 17,045
Re: Effect of Prop Antifouling on Prop Anode Wear?

Quote:
Originally Posted by duefocena View Post
Would painting the prop foil the contact between the zinc and the prop? I have H-5 Autoprops and go through my prop anodes every 6-9 months or so. The shaft zincs last about 3-4 months and I've added a galvanic isolator as well as a " Billy Bass" ( clip on 1 kilo zinc ). Attributing the galvanic action to old docks with a lot of electrical leaks I replace them regularly rather than risk the props. When I found they were wearing mostly at the screw holes, I painted the holes and corners leaving the base clean to make contact. This made them last twice as long.

Yes, you have to have metal to metal contact for an anode to function correctly

I think your Billy Bass may be helping your anodes last longer
__________________
a64pilot is offline   Reply With Quote
Old 10-03-2016, 09:23   #12
Registered User
 
Sailor647's Avatar

Join Date: Feb 2013
Location: Hailing Port: Portland, Oregon
Boat: Norseman 400
Posts: 197
Re: Effect of Prop Antifouling on Prop Anode Wear?

We painted our newly rebuilt Max Prop with Marlin Paints "Velox Plux Antifouling for Propellers" (purchased through PYI, near Seattle) in July, 2015. It is a two coat process. (Green primer, then white antifouling.) We did NOT apply either the primer or the antifouling underneath any of the zincs.

We check the zincs monthly, or thereabouts. The last check of the underwater zincs was last Saturday (March 5, 2016) - 7 months after install and launch. The prop and shaft zincs are still at about 80% or better. The bar zinc on the rudder is about 50%. The four half-dollar sized zincs for the Frigoboat keel cooled refrigeration system have to be replaced every 3-4 months.

Hope this helps!
Attached Thumbnails
Click image for larger version

Name:	IMG_1469.jpg
Views:	171
Size:	409.4 KB
ID:	120373   Click image for larger version

Name:	IMG_1478.jpg
Views:	169
Size:	404.7 KB
ID:	120374  

Click image for larger version

Name:	IMG_1769.jpg
Views:	173
Size:	401.4 KB
ID:	120377   Click image for larger version

Name:	IMG_1475a.jpg
Views:	166
Size:	417.1 KB
ID:	120378  

__________________
Sailor647 is offline   Reply With Quote
Old 10-03-2016, 09:40   #13
Registered User
 
leftbrainstuff's Avatar

Join Date: May 2011
Location: San Francisco and Australia
Boat: Liberty 458
Posts: 1,978
Re: Effect of Prop Antifouling on Prop Anode Wear?

Quote:
Originally Posted by Sailor647 View Post
We painted our newly rebuilt Max Prop with Marlin Paints "Velox Plux Antifouling for Propellers" (purchased through PYI, near Seattle) in July, 2015. It is a two coat process. (Green primer, then white antifouling.) We did NOT apply either the primer or the antifouling underneath any of the zincs.

We check the zincs monthly, or thereabouts. The last check of the underwater zincs was last Saturday (March 5, 2016) - 7 months after install and launch. The prop and shaft zincs are still at about 80% or better. The bar zinc on the rudder is about 50%. The four half-dollar sized zincs for the Frigoboat keel cooled refrigeration system have to be replaced every 3-4 months.

Hope this helps!
We too prop coat. Its wears away particularly at the tips and leading edge. Prop coating minimises pitting corrosion but has no measurable impact on anode depletion. We recoat annually at each haulout.

The frigoboat keel cooler zincs are tiny. We keep the keel cooler seperate from our main bonded circuit. Otherwise those tiny zincs become the most sacrificial (concentration of current on a small surface area) of all zincs. You want the largest surface anodes to be the most sacrificial. This will maximize both protection and anode replacement schedules.

As anodes deplete the current concentration increases due to the decreasing surface area. Depletion is non linear. Ideally plan to change zincs when half worn.

A monthly inspection schedule and prop coating at haulout is a good example of best practice. A go pro on a stick works well when the water is clear.

We also conduct a corrosion inspection / survey each month to confirm there are no issues with our bonded circuit.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app
__________________
leftbrainstuff is offline   Reply With Quote
Old 10-03-2016, 11:30   #14
Registered User
 
UNCIVILIZED's Avatar

Join Date: Jun 2014
Location: Up the mast, looking for clean wind.
Boat: Currently Shopping, & Heavily in LUST!
Posts: 5,629
Re: Effect of Prop Antifouling on Prop Anode Wear?

A few questions & thoughts:

- Why on earth do you need to haul out in order to change out your zinc? That has to be crazy expensive, given how often your doing it, coupled with your boat's size. Non?

- Fiscally, it only makes sense to switch to a prop where the above isn't the case. Especially as there are more efficient propellers out there.
Because between; not needing to haul in order to change zincs, not needing to change zincs so frequently, & getting better prop performance (under sail AND power), it only make sense to change to another brand/type.
I mean the new prop would pay for itself in under a year, even without selling the old one. Which is obviously possible, & advisable.

- How cold can the water be?
I mean I regularly swim in tne N. Sea when I'm over in Scotland. Ditto in Puget Sound, where water temp. is 40 - 45 deg. F (5-8 deg. C).
Without a drysuit or wetsuit, in the dead of Winter, out near the Pacific Coast (Ocean proper).

Also, there are no shortage of divers in the PNW; recreational, & commercial, who only wear wetsuits. So I can't see water temp being that big an issue, regardless.
I mean guys even dive though the ice, sans heated wetsuits. Which are what professional divers wear when working in very cold waters for extended periods.

- Why not switch to a bigger zinc? Even if it means either; having some oversized zincs custom machined, the prop. machined, or both?

- Has anyone done a current survey in your marina, like your insurer for example? As if there's stray current in there, I'm SURE that they'd take a STRONG interest in it.

- Have you tried hanging a zinc fish which is directly connected to your shaft?

- There are other options as well, in order to literally stop such problems. But they're a bit exotic, & Far too expensive for this application.


PS: The part about more efficient propellers has been covered extensively on here before; including a posting of the test in the May '09 Yachting Monthly magazine. Plus, of course, there's lots of info on same via an online search.
__________________

The Uncommon Thing, The Hard Thing, The Important Thing (in Life): Making Promises to Yourself, And Keeping Them.
UNCIVILIZED is offline   Reply With Quote
Old 10-03-2016, 11:39   #15
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Albany Ga.
Boat: Island Packet 38
Posts: 17,045
Re: Effect of Prop Antifouling on Prop Anode Wear?

I'll bite, from an efficiency perspective what prop is more efficient than an Autoprop, and why?

BTW, I think his haul rate is peanuts from his local club there, compared to customary cost for a boat of that size.
__________________

__________________
a64pilot is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Need help finding a suitable prop anode bony Engines and Propulsion Systems 32 04-07-2015 18:23
Unusual prop zinc anode F51 Construction, Maintenance & Refit 10 08-11-2014 15:45
Wear and Spalling on the Prop Shaft . . . SabreKai Engines and Propulsion Systems 0 23-11-2011 16:46
Shaft Anode and Prop Anode ? Weyalan Propellers & Drive Systems 13 16-09-2010 22:04



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 06:34.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.