zinc question to the forum

[Al]

Had my boat bottom swept after a six months period preceded by a haul out a year before that. At each point the zincs, all of them, were deemed to be in great condition. Not possible!!! So I have been inquiring from the wizards of smart on the waterfront here in SE Alaska, with really no satisfaction. Of course the term "Bonding" comes into play almost at the first inquiry, however, none of the fellows can give a definition or schematic of what "Bonding" looks like. There is no paint under the zincs placed on the rudder, There is a prop cape (The wheel polished by the diver is stated to be "Shiny Brass", no pink or reddish color.
The bar zinc on the rudder support and the three swim step struts are the remaining zincs.

There is no apparent corrosion showing anywhere on the engine. The pencil

zinc in the cooling system is normal for its six months change out.
The local machine shop that provides excellent prop repair services, suggested that I have a "Clean" boat . Hummmm. Boats around me are experiencing normal zinc wear calling for periodic replacement.
I have owned the boat for near 10 years and was in the practice of changing all the zincs on annual haul out and bottom paint. At those times the hub zinc would be the worst for wear allowing the other zincs to 'Maybe" last another season, but would change them anyway.
So fellow forum members, of smart! Let me know the universal thinking.
Cheers
Al

Frustrating, to say the least.

 

[C lectric]

When you install zincs do you check the electrical continuity between the zinc and the metal it is supposed to protect?

I always use my ohmmeter after the installation. If the meter shows over 1 ohm then I pull the zinc and redo it. Ideally the meter will show 0 ohms or in the few 10ths of an ohm.

All zincs get a wire brushing of the contact area before installing.
All installation areas on the part are also sanded or wire brushed.
My drill with some rotary wire brushes see good use at this time.

Even light corrosion will insulate the zinc and the part.

I have had zincs that lasted the normal change out interval in great shape.
When checked the resistance was way to high meaning the connection was no good.

Bonding will not help if the zincs are not mounted properly.

 

[KnotYet]

Some boats with grounding issues that plug in to shore power can affect yours.
It is possible that you had a 'hot' boat neighbor that has left your dock vicinity.
Another possibility is the dock wiring that could have been changed or improved.

 

[tiltrider1]

I would start with C lectric’s advice. When ever I haul out I check all my under water medals for continuity to my big zink plates.

Another possibility is that your zinks were exposed to fresh water and then dried out before being installed. The zink could have created an oxidation coating and will no longer function.

did you get a new neighbor? Is he going through zink quickly? If so he might be protecting your boat for you.

If just one of your zinks was doing all the work I would suggest the possibility of dissimilar zink compounds but that doesn’t sound like your issue.

 

[Comodave]

Start with Clectric suggestions.

 

[alormaria]

My zincs rarely ever looked like they had been underwater.



Then I switched to aluminum anodes. Hoo Chee Momma!



I'm in fresh water.

 

[Comodave]

Yes, zinc anodes in freshwater get a coating on them ond they become ineffective. I only use aluminum anodes since they are good in any type of water. If the anodes are not wasting away they are not doing their job.

 

[Bmarler]

The only way to really know if you’re protected is to survey with a silver half cell. Check everything metal that penetrates the hull. Anything else is just a guess.

 

[Al]

C Lectric- Sorry for the delay in a response. I have been out boating where no internet exist. Thank you for a clear plan. I will not rebut you as you are in the know, however a couple of comebacks and perhaps clarification. The yard that installed the zincs three seasons back has been doing my zincs/bottom pain for ages, same crew. I am aware of the zincs having to be clear of paint underneath One in error maybe, but to have the rudder zinc, the rudder support strut, and the three on the swim step all clear would indicate some other issue than paint under the zinc. Then, the hub zinc is clearly not going to have paing involved. Nobody I know in our part of Alaska paints their wheels, rather they shine them to bright brass color IMonel?)
I am not to hep on using electronic gadgets to measure resistance or such but I am going to show your post to my engine shop that may have the knowledge to point the way to learning or asking my shop if they can provide this check, again I will copy them with your post

To the other posters who responded, Thanks, Fresh water has no
application to a solution in this case. Yes, boats around me have normal loss of zinc protection , One marine machine shop that specializes in wheel refurbishing suggested I have a "Clean Boat" that zincs are not affected. AI do not agree,
Thank you again, your response will set me on finding the process. It is important enough that a haul out cost after the in water brushing is worth the effort
Al-Ketchikan

When you install zincs do you check the electrical continuity between the zinc and the metal it is supposed to protect?

I always use my ohmmeter after the installation. If the meter shows over 1 ohm then I pull the zinc and redo it. Ideally the meter will show 0 ohms or in the few 10ths of an ohm.

All zincs get a wire brushing of the contact area before installing.
All installation areas on the part are also sanded or wire brushed.
My drill with some rotary wire brushes see good use at this time.

Even light corrosion will insulate the zinc and the part.

I have had zincs that lasted the normal change out interval in great shape.
When checked the resistance was way to high meaning the connection was no good.

Bonding will not help if the zincs are not mounted properly.

 

[C lectric]

It does not have to be paint to goof up those interfaces.
Corrosion /oxidation will do it. Even light corrosion/oxdidation.

I don't think I even mentioned paint except as something to get rid of where a zinc is mounted.

I used to trust an otherwise knowledgeable fellow to do my zincs. Untill one year I had a totally untouched zinc on my STEEL keel. Sheepdip. My change interval is 2 yrs and there is no way that zinc should not have corroded. The other 5 zincs on that keel were corroded, 3 per side.

I grabbed my ohmmeter and checked. I don't remember the actual reading but the zinc may as well not have been there, no continuity.

I did explain what I was doing with my ohmmeter and why. I think he got it.


Of course I installed new zincs as it was my haul out time and I had them. I recall reusing that zinc and next time around it too was corroded.

The difference was the mounting faces were not cleaned. properly.
I have similar experiences since, when I did not properly wire brush both the metal to be protected and the zinc mounting face.

I caught them because I used my DMM ohms function.

If I remember correctly the ONLY metal whose oxide is conductive is silver.
All others become insulators to varying degrees.

So a clean mounting surface is imperative.

If you are not used to dealing with meters then it would be worthwhile to learn. You don't need to become expert but many electrical problems can be worked out with even a limited ability to use one.

Often the paint is close to the zinc so I will often go from zinc to zinc on the same piece of metal. If the meter shows O or near zero ohms then the connections are good.

I do this with zincs on the keel, on the shaft, on the rudder and the prop to double check there is a connection as the prop depends upon the shaft mounted zincs.

Sorry about the long winded reply. I hope it helps.

 

[Al]

No need to apologize as the content is worthy of detail. Your responses are the one of the intent of the forum's existence. In short, the marine surveyor who I had inquired on the subject, called me back with the name of a yet not introduced, electrical marine technician, spoke professionally of. I have make email contact with a response of two weeks out (Side line occupation)
I will keep you (and the interested members) informed of the outcome.
Thanks again
Al-Ketchikan

It does not have to be paint to goof up those interfaces.
Corrosion /oxidation will do it. Even light corrosion/oxdidation.

I don't think I even mentioned paint except as something to get rid of where a zinc is mounted.

I used to trust an otherwise knowledgeable fellow to do my zincs. Untill one year I had a totally untouched zinc on my STEEL keel. Sheepdip. My change interval is 2 yrs and there is no way that zinc should not have corroded. The other 5 zincs on that keel were corroded, 3 per side.

I grabbed my ohmmeter and checked. I don't remember the actual reading but the zinc may as well not have been there, no continuity.

I did explain what I was doing with my ohmmeter and why. I think he got it.


Of course I installed new zincs as it was my haul out time and I had them. I recall reusing that zinc and next time around it too was corroded.

The difference was the mounting faces were not cleaned. properly.
I have similar experiences since, when I did not properly wire brush both the metal to be protected and the zinc mounting face.

I caught them because I used my DMM ohms function.

If I remember correctly the ONLY metal whose oxide is conductive is silver.
All others become insulators to varying degrees.

So a clean mounting surface is imperative.

If you are not used to dealing with meters then it would be worthwhile to learn. You don't need to become expert but many electrical problems can be worked out with even a limited ability to use one.

Often the paint is close to the zinc so I will often go from zinc to zinc on the same piece of metal. If the meter shows O or near zero ohms then the connections are good.

I do this with zincs on the keel, on the shaft, on the rudder and the prop to double check there is a connection as the prop depends upon the shaft mounted zincs.

Sorry about the long winded reply. I hope it helps.

 

[Steve DAntonio]

When you install zincs do you check the electrical continuity between the zinc and the metal it is supposed to protect?

I always use my ohmmeter after the installation. If the meter shows over 1 ohm then I pull the zinc and redo it. Ideally the meter will show 0 ohms or in the few 10ths of an ohm.

All zincs get a wire brushing of the contact area before installing.
All installation areas on the part are also sanded or wire brushed.
My drill with some rotary wire brushes see good use at this time.

Even light corrosion will insulate the zinc and the part.

I have had zincs that lasted the normal change out interval in great shape.
When checked the resistance was way to high meaning the connection was no good.

Bonding will not help if the zincs are not mounted properly.

Agree on all counts except the wire brush, use a non-metallic abrasive such as a ScotchBrite pad instead, a wire brush can introduce another metal to the interface between anode and cathode.

 

[Art]

Al - My Pal!!

Always good to experience you on TF... Your "zinc-question" thread is currently of special interest to me.

Because:

For 14 yrs been keeping our Tolly in SF Delta's freshwater [first time I ever kept a boat in freshwater]. Such a gentle way to dock; regarding corrosion as well as keeping bottom clean... simply loved it!!

Well... those EZ Daze are over - for now! This month will cruise her back into SF Bay saltwater to berth for at least some time. For decades on east coast as well as west coast saltwater was where my boats floated. I well recall often changing zincs, cleaning bottoms... more often haul-outs too.

Anyway - Moving forward... I keep hearing that aluminum anodes have become the preferred material for best protection in any consistency water.

Currently I've got magnesium anodes on her. Don't imagine mag will last long in saltwater. Planning to soon replace with zinc or aluminum. Hope some of knowledge chime in regarding aluminum anode.

Regarding your boat zinc's lasting a long duration: Over decades I've found that by not plugging in our boat to the dock [on anywhere near a continual, nonstop basis], not docking it in a "hot" marina and making sure that all batts on the boat are completely isolated when boat is left resting at a dock works well to reduce anodes from wasting away. Do you do those types of anti corrosion alternatives.

Attached are photos of our soon to be vacated SF Delta freshwater, covered dock and the soon to be filled SF Bay saltwater, wide open berth.

Change is the only thing that's constant!

Last photo is [2008] in same marina as the new berth we'll be taking

 

[Comodave]

Yes, I would use aluminum anodes if you are going to be in salt water. It works in fresh or salt. Definitely get rid of the magnesium anodes for salt water.

 

[Art]

Yes, I would use aluminum anodes if you are going to be in salt water. It works in fresh or salt. Definitely get rid of the magnesium anodes for salt water.

From what I know... mag will soon be gotten rid of by the salt water itself.

You use aluminum I guess. How is it in saltwater for life span and protection?

Recommendation for outlet to purchase from?

 

[Comodave]

Not sure exactly how long they last in saltwater. I get them from boatzincs.com.

 

[Bacchus]

Don't forget to switch over and engine / gen pencil anodes.
I have found Performance Metals my favorite. Wide selection of alum sizes, steel wire in center to minimize breakage & loss of stubs.
Defender & others carry then but I have gone directly to PM for some less common sizes when I couldn't find them elsewhere.

 

[Steve DAntonio]

Zinc consumption has nothing to do with dock wiring or "hot marinas" see https://stevedmarineconsulting.com/wp-content/uploads/2019/09/Hot-Marina-Myth-CW-AugSept-2019.pdf for details on that subject. With very few exceptions corrosion is a DC phenomenon.

A vessel adjacent to yours can be an issue, it can increase the consumption rate of your anodes, if you have no functioning galvanic isolator, or it can extend the life of your anodes, although that's less common.

When ever the question of zinc consumption rate comes up, my response is the same, carry out a reference cell test, it is the only way to know if you are properly protected, and check integrity of your bonding system, that needs to be done while hauled.

Do you have a galvanic isolator that meets current ABYC A-28 standards? If it's original to the boat it probably does not.

If anodes aren't being consumed it could be indicative of a bonding system issue, or the anodes haven't been installed properly, over clean surfaces, that's easy to test with a multimeter while hauled.

The anodes used for the engine/gen and other internal heat exchangers are completely unrelated to those on the hull; for corrosion purposes they are in a different body of water and thus have no interaction with each other.

Aluminum anodes are ideal as they work in fresh, brackish and salt, magnesium should only be used in fresh water.

If you do hire someone to analyze this, they should have an ABYC Corrosion Certification. It's a subject that's poorly understood even by those in the industry, that certification ensures they at least understand the basics of corrosion.

 

[Art]

Hi Steve - I greatly appreciate your learned knowledge.

interesting statement at close of your post, 18:

"If you do hire someone to analyze this, they should have an ABYC Corrosion Certification. It's a subject that's poorly understood even by those in the industry, that certification ensures they at least understand the basics of corrosion."

Boy - Say Howdy!! Ain't that the truth!!! LOL

At 70 yrs old, boating from birth and having been entailed in 60 years plus of boat maintenances since being old enough to understand corrosion and galvanization circumstances in saltwater [e.g., owning boats, lobstering on down east boats, servicing others' boats, building new boats in a factory, years of being a young yard hand at marinas, launching boats off travel lifts, berth/slip placements... etc, etc] I've seen and experienced my share of boats that have anodes providing good service, poor anode service and no anodes at all.

IMO - Far as I can tell from 60 yrs of hands-on experience, not book learning [and never having lost any "primary water contact" metal part to corrosion on any boat that has been mine or in my family]:

1. Make Sure - anodes are always kept in positions required and change when appropriate wasting away of the anode has occurred
2. Do Not - leave a boat connected to the dock by electric wire
3. Be Sure - to have inline [Perko https://www.perko.com/catalog/category/battery_switches/ or other manufacturer] main breaker switch to turn off [100% isolate] all batteries when leaving boat at dock

Side Note: Make sure your boat does not leak or check often for turning back on the isolating breaker to activate bilge pumps. And, always have your insurance paid-up!

Those three rules are what I follow... From decades experience - that works for me!

 

[Tator]

A question concerning anodes in the heat exchanger. Can you over zinc the heat exchanger? After being unable to find the recommended zinc one year, I used a larger zinc and have continued to do so as it would last my whole cruising season. I put new ones in before I leave the boat for the winter. I find a buildup of white powder around the bung for the zinc as well as the edges of the endcaps and the edges endcap bolt when I return in the Spring. As the exchanger sits higher than the sea level it seems hard to attribute it to saltwater leakage.

Tator

 

[Al]

Zinc consumption has nothing to do with dock wiring or "hot marinas" see https://stevedmarineconsulting.com/wp-content/uploads/2019/09/Hot-Marina-Myth-CW-AugSept-2019.pdf for details on that subject. With very few exceptions corrosion is a DC phenomenon.

A vessel adjacent to yours can be an issue, it can increase the consumption rate of your anodes, if you have no functioning galvanic isolator, or it can extend the life of your anodes, although that's less common.

When ever the question of zinc consumption rate comes up, my response is the same, carry out a reference cell test, it is the only way to know if you are properly protected, and check integrity of your bonding system, that needs to be done while hauled.

Do you have a galvanic isolator that meets current ABYC A-28 standards? If it's original to the boat it probably does not.

If anodes aren't being consumed it could be indicative of a bonding system issue, or the anodes haven't been installed properly, over clean surfaces, that's easy to test with a multimeter while hauled.

The anodes used for the engine/gen and other internal heat exchangers are completely unrelated to those on the hull; for corrosion purposes they are in a different body of water and thus have no interaction with each other.

Aluminum anodes are ideal as they work in fresh, brackish and salt, magnesium should only be used in fresh water.

If you do hire someone to analyze this, they should have an ABYC Corrosion Certification. It's a subject that's poorly understood even by those in the industry, that certification ensures they at least understand the basics of corrosion.

Thanks Steve, appreciate you being knowledgeable and willing to share.
As I indicated, and believe fortunate, to have a marine electrical fellow who is employed by our local Vigor ship yard, who has a side gig assisting boaters.
"

That I had no issue with annual replacement of my zincs and did so knowing I was accomplishing the intent. Now, that NONE of the zincs are showing corrosion, I am concerned as I have not found any indication anywhere on the boat fittings or engine. The diver confirmed no pink or reddish on the wheel. said it cleaned up shined with a brushing.


There has never been any continued connections between any of the zincs.
There has been no modifications to the boat in this period.
Per earlier post to "C"- There is no large external zinc plate mounted on the stern with proper thru bolts. and no "Feather" on the shaft.


No matter, The boat is scheduled this fall for a haul. For sure the surface's will be bare, still the hanging question is that the hub zinc too is showing no corrosion. This is clearly a zinc to bronze/stainless application and in the past when ware is positive, almost eaten away annually,now clean??



Putting some faith in the engineer , and asking my boat yard if they can do the current checking gismo.


Cheers, will post first the outcome with the engineer, and as that result, the fall zinc change.


Al-Ketchikan

 

[Steve DAntonio]

Al:
Keep us posted.
Your prop is probably manganese bronze, which is actually brass is it contains zinc, it can dezincify if not protected by an anode, so worth checking the voltage on the shaft using the reference cell.

 

[Steve DAntonio]

A question concerning anodes in the heat exchanger. Can you over zinc the heat exchanger? After being unable to find the recommended zinc one year, I used a larger zinc and have continued to do so as it would last my whole cruising season. I put new ones in before I leave the boat for the winter. I find a buildup of white powder around the bung for the zinc as well as the edges of the endcaps and the edges endcap bolt when I return in the Spring. As the exchanger sits higher than the sea level it seems hard to attribute it to saltwater leakage.

Tator

Some kind of accretion or calcareous deposit. Reaction with hydroxides released at cathodes. Likely a combination of calcium carbonate and magnesium hydroxide. All kinds of ions floating around in the electrolyte, and the cathodes are very negative so all kinds of ionic activity at those sites. It’s a coating by Mother Nature.

They actually use this process to protect the underwater metals on oil drilling structures. They use mag anodes on the steel with no coating. The calcareous deposits become the coating. Of course there are anodes to protect the steel. But as the coating develops less and less anode loss occurs (like the difference between painted and unpainted metal….the painted metal requires less protection which means the anodes start lasting longer and longer.)

 

[Al]

To Steve and forum- Update- The young fellow (any under 80) contacted me and assured me that assistance was possible. He came on board and proceeded to confirm that he was ABYC and NMEA certified. He was employed by VIGOR to be involved with the electrical wiring on the two new Alaska State ferries, a two year job. He proceeded as well in (1) find the bonding system I never knew existed. He traced it by instrument
and advised that while there was signs not enough to provide protection, least of the rudder area where there is no sign of any bonding. He projects that he cab redo the system as the internals allow. Hopefully that will suffice. Yes, he is recommending aluminum over zinc. As I have a tentative date to haul in the late summer in Wrangell, a inspection of the shaft for pitting will take place,

However, my local diver indicates that he can provide a "ProGo" (I think that is what he called it, a video of any other word) and of course, would be available for changing the aluminum units. I have to cross reference with the diver and the electrical fellow
to confirm agreements.
On a side note- I advised the technician that I was underway of finding the fault on not being able to engage the starter or panel accessories due to my having inadvertently crounded the positive of a new battery with the ground cable in the dark of the engine compartment using a small flashlight. I had been a couple of part days seeking out the error without success at this point. He casually said he'd take care of that in couple of minutes following the research on the ground issue.
When he did look into it, I would say that he found the fault within 10 minutes. So if nothing else, the time paid was worth every nickel.
Now, I will continue the update following the completion of this fellow' efforts in the coming days as I come back up on his busy schedule.
Al-Ketchikan

 

[Comodave]

Sounds like you found a great electrician. Don’t loose his number!

 

[Art]

Al... !!

Did you discuss with the expert "why" anode zinc metal on your boat was not being eaten-up... yet no corrosion noted on metal diode portions?

I believe my question is formed correctly regarding some items in your previous posts.

 

[Al]

Al... !!

Did you discuss with the expert "why" anode zinc metal on your boat was not being eaten-up... yet no corrosion noted on metal diode portions?

I believe my question is formed correctly regarding some items in your previous posts.

Art, My attempt to answer would only prove the use and need for acquiring a qualified person to answer. His explanation at the time seemed reasonable, but darn if I am able to translate. We will just have to wait till he returns and goes to work.
Al

 

[Art]

Art, My attempt to answer would only prove the use and need for acquiring a qualified person to answer. His explanation at the time seemed reasonable, but darn if I am able to translate. We will just have to wait till he returns and goes to work.
Al

Al, as you, I too have been around marine doings for many decades... and, it seems I'm just as confused as you! Also appears, others on TF are in a holding pattern waiting for explanation.

Maybe in our latter years God gives us a break regarding metal corrosion! Yeah right... LOL :lol:

 

[Al]

C- Thanks to your post and the recommended "Listen to Clectric's" I employed a certified marine electrical fellow who recently moved to Ketchikan and has established his business. He came to Ketchikan three years past employed by our shipyard to wire the two new Alaska State ferries. So- C, He about quoted you in total. He has totally replaced the bonding system and the remaining need is to do as you and others suggested, wire brush each zinc's medal surface prior to replacing each zinc. while he didn't do a over the side with a test zinc at this time, he will upon my return from having the bottom painted and zincs replaced. Will keep the forum posted.
Al-Ketchikan

When you install zincs do you check the electrical continuity between the zinc and the metal it is supposed to protect?

I always use my ohmmeter after the installation. If the meter shows over 1 ohm then I pull the zinc and redo it. Ideally the meter will show 0 ohms or in the few 10ths of an ohm.

All zincs get a wire brushing of the contact area before installing.
All installation areas on the part are also sanded or wire brushed.
My drill with some rotary wire brushes see good use at this time.

Even light corrosion will insulate the zinc and the part.

I have had zincs that lasted the normal change out interval in great shape.
When checked the resistance was way to high meaning the connection was no good.

Bonding will not help if the zincs are not mounted properly.

 

[C lectric]

Agree on all counts except the wire brush, use a non-metallic abrasive such as a ScotchBrite pad instead, a wire brush can introduce another metal to the interface between anode and cathode.

Steve,

I will be properly prepared next time. Scotchbrite wheels. I had some, just didn't think of the steel particles left on the zinc.