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post #21 of 32 Old 11-12-2016
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Re: Sad looking zinc's

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Electrons don't lie or take sides.
I'm not sure how you could read anything I wrote as saying otherwise. The facts are that an aluminum anode has 3x more current capacity than an equal mass zinc anode, while only being 4-5% more galvanically active than an equal mass of zinc anode.

So for the same physical size instead of mass, aluminum anodes have 30-50% more lifespan than zinc anodes. This is the summation of the balance between the increased galvanic activity with the increased current capacity adjusted for the difference in mass. There are only so many electrons to give in a fixed mass of metal, and an equal sized aluminum anode has 30-50% more of them to begin with compared to a zinc anode.

This doesn't break any laws of physics, electrics or chemistry. In fact, it supports them.

Again, a google search will support these facts. But please, let's deal with facts and not just stating training and education differences (you don't know mine).

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post #22 of 32 Old 11-12-2016
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Re: Sad looking zinc's

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Originally Posted by davidpm View Post
These are the zinc's at the end of the school year on one of the school boats.
Even with the bad picture I think you can see they are mostly gone.

Does this mean that damage was done since they are so badly eaten up.

Should we put on three next year?

The other boat had zincs in much better condition.

What else should we look for or fix?
I'll assume that this is the O'day 35 because that strut looks familliar.

I put two different brands of zinc on my propshaft, and wrote about it in another thread; https://www.sailnet.com/forums/gear-m...endations.html

In that thread I shared that one of my zincs was gone after 5 months, and the other looked worn, but was still there.
Quote:
Here are two zincs; The one on the right was installed in early August, and the remenants on the left has been there since the boat was launched in April:
I also shared this;


Quote:
I was finally able to figure out what brand of zinc lasted so long.

In my pic above, the remains of the zinc on the left, which lasted 5+ months is a B&S ~ $19. The zinc on the right, a Camp was only in the water for 2 months. The predecessor to the zinc on the right, also a Camp, fell off at less than 4 months. IMHO it is worth paying 2x for a zinc that will last twice as long because it will save me from having to change the zinc in the water. While I have a lot of respect for Maine Sail's recommendadtions, I am NOT going to spend $43 each (5X the price of a Camp) for sacrificial zinc anodes.

I wish that I could have figured this out before I bought a supply of six Camp zincs... Going forward, I will spend the extra $ for a B&S.

Hopefully, some of you will learn from my mistake.
Bottom line is that the zincs SHOULD wear away after 5 or 6 months in the water, and the quality of the zinc makes a big difference.

[EDIT]P.S. Please stop using the Sailnet upload image feature. It sucks, and I will usually not click on the thumbnail to look at it. Use any other image hosting service, and the '[IMG]' delimiter.


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Last edited by eherlihy; 11-12-2016 at 10:03 PM.
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post #23 of 32 Old 11-12-2016
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Re: Sad looking zinc's

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Originally Posted by boatpoker View Post
The vast majority (every corrosion survey I have done) of stray current corrosion cases are caused by the boat suffering the problem however it can be caused by other vessels nearby.

I'm outahere. As usual with this issue there are many opinions posted of little value by untrained, uneducated people.
Certified Corrosion Analyst.
Unfortunate if you have relevant expertise and are "outahere". Maybe you could hang in here and educate some folks.

That said, you may be surprised that some of the "undeducated" folks out there are providing valid experiential evidence of phenomena. For my own part, I have been using zincs from the same source for many years, but have experinece various results, from losing my MaxProp tailcone zinc one season to having the tailcone zincs remaining 90+% intact for the past 2 years.

I am at a private dock and rarely hook up shore power and there are no obvious stray current sources anywhere nearby. What did seem to make a big difference during the past 4 seasons is using spray zinc on my prop. Also, I electrically insulated the ground plates for my former SSB from seawater. Those ground plates had been a barnacle farm for years and now that problem has gone away.
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post #24 of 32 Old 11-13-2016 Thread Starter
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Re: Sad looking zinc's

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Originally Posted by boatpoker View Post
The vast majority (every corrosion survey I have done) of stray current corrosion cases are caused by the boat suffering the problem however it can be caused by other vessels nearby.

I'm outahere. As usual with this issue there are many opinions posted of little value by untrained, uneducated people.
Certified Corrosion Analyst.
Totally get how annoying it is when folks speak authoritatively about stuff they are misinformed about.

I started this thread and would appreciate you hanging around clearing up misconceptions, if you don't mind. It is knowledgeable people that make Sailnet valuable.

Most of us are not arguing with you.

So to summarize:

1. One or two zinc's
2. What brand, we usually get them from WM
3. Get a reference zinc and check boat with Multi-meter.
4. Check for leaking wire in bilge

What do you recommend?

The lesson from the Icarus story is not about human failing.
It is a lesson about the limitations of wax as an adhesive.
If you have an engineering problem solve it.
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post #25 of 32 Old 11-13-2016
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Re: Sad looking zinc's

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Originally Posted by davidpm View Post
Totally get how annoying it is when folks speak authoritatively about stuff they are misinformed about.

I started this thread and would appreciate you hanging around clearing up misconceptions, if you don't mind. It is knowledgeable people that make Sailnet valuable.

Most of us are not arguing with you.

So to summarize:

1. One or two zinc's
2. What brand, we usually get them from WM
3. Get a reference zinc and check boat with Multi-meter.
4. Check for leaking wire in bilge

What do you recommend?
The guy claims that aluminum anodes are inferior to zinc in saltwater. That disqualifies his opinion on the subject immediately, IMHO.


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post #26 of 32 Old 11-14-2016 Thread Starter
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Re: Sad looking zinc's

This article says there are no downsides to aluminum anodes in salt water other than cost.

Zinc and Aluminum Sacrificial Anodes | Cruising World

don Casey also recommends aluminum

BoatUS €“ BoatTech €“ Sacrificial Zincs by Don Casey

Jamestown says that aluminum anodes last longer due to higher capacity.

The lesson from the Icarus story is not about human failing.
It is a lesson about the limitations of wax as an adhesive.
If you have an engineering problem solve it.

Last edited by davidpm; 11-14-2016 at 06:06 PM.
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post #27 of 32 Old 11-14-2016
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Re: Sad looking zinc's

Cost would only be a negative for the really, really, really cost sensitive person. For example, a 1.5" shaft zinc anode costs $9.46 while the corresponding sized aluminum anode cost $10.38. (boatzincs.com)

That extra $0.92 saved won't even buy you a candy bar.

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post #28 of 32 Old 11-15-2016
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Re: Sad looking zinc's

Easy to find shaft anodes in aluminum. Since "all" anodes must be the same metal, it would be harder to source aluminum for the shaft cutter, max prop and diesel. The pencil zincs for my diesel are hard enough to source in zinc actually.


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post #29 of 32 Old 11-15-2016
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Re: Sad looking zinc's

Pretty much everyone sells aluminum anodes for max prop (and many other props) - even West Marine. The engine anode is really not that important to be the same, but aluminum pencil anodes in most sizes are available everywhere also - West Marine, Defender, etc. The only cutters I have experience with did not have anodes (shaft shark and stripper), so I don't know about aluminum availability for those that do. Most cutters are attached to the shaft or prop and get protection from those anodes, so I don't know what else needs protection on one. Does yours also offer magnesium anodes? If not, then it couldn't be used in fresh water, which would be odd.

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Re: Sad looking zinc's

I suppose they might exist somewhere, but I've not seen aluminum Spurs cutter anodes. The cutter does have plastic bushings, which is why I suspect it needs its own. I would be interested in a source for these. I've never seen aluminum max prop anodes in 70mm at my local WM, it's hard to even find them in stock in zinc. Perhaps online somewhere? The diesel zincs I referenced are actually for the MASE generator, which I also find hard to locate, even in zinc, other than from MASE directly. That's very frustrating.


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