Dave S
Active Member
Weight is much different between zinc and aluminum. That can help you determine what's what. OEM yamaha anodes are aluminum.
Sacrificial Anode: Zinc vs Aluminum
- Thread starter Peahead
- Start date
Weight is much different between zinc and aluminum. That can help you determine what's what. OEM yamaha anodes are aluminum.
I was told never to mix the two..all zinc or all aluminum. BTW zinc will break down faster than aluminum being a softer metal. Zinc therefore makes a better sacrificial anode, so long as they are kept in good shape. I also bond all underwater metals into one bonded system and have zincs on my tabs, pod and engines. The largest is a bar type on the pod...it gets welded onto some tabs on the bottom of the pod. I replace all the bonding wires and connections each spring with new, clean up all the contact surfaces and protect the connections with heat shrink and LPS3. I use a green 10 gauge copper/tin marine grade wire for bonding wire.
Peahead
Well-Known Member
So by "better" can I assume you mean that because they break down faster that means they are better because they have a higher protection ?
Ok now I am just as confused ...........so why do I keep seeing suggestions that Aluminum offers higher protection AND lasts longer ?
Eg:
Navalloy Sacrificial Anodes from Performance Metals:
" Specifically designed for preventing corrosion on Yamaha engines, the versatile Aluminum Yamaha Anode Line provides a higher protection voltage than zinc and lasts 30 to 50% longer"
http://www.off-road.com/dirtbike/tech/new-line-of-anodes-protect-yamaha-engines-35374.html
This place claims the Aluminum (Navalloy) anodes they market are up to 50% longer lasting but also have higher protection voltage than zinc ? Is this possible or are these just marketing claims that are simply untrue scientifically (and in practice) ?????
Ok now I am just as confused ...........so why do I keep seeing suggestions that Aluminum offers higher protection AND lasts longer ?
Eg:
Navalloy Sacrificial Anodes from Performance Metals:
" Specifically designed for preventing corrosion on Yamaha engines, the versatile Aluminum Yamaha Anode Line provides a higher protection voltage than zinc and lasts 30 to 50% longer"
http://www.off-road.com/dirtbike/tech/new-line-of-anodes-protect-yamaha-engines-35374.html
This place claims the Aluminum (Navalloy) anodes they market are up to 50% longer lasting but also have higher protection voltage than zinc ? Is this possible or are these just marketing claims that are simply untrue scientifically (and in practice) ?????
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Dave S
Active Member
Hey Rollie, you have any proof of this? I have been told the opposite and according to the anodes on my motor, the aluminum broke down much quicker than the zinc.
Wwunder
Member
I'm no expert, but I read that you shouldn't mix the zinc and aluminum anodes because the higher protection voltage of the aluminum (over the zinc) will then use part of its capacity to protect the zinc. The result being that the aluminum breaks down first. Seems consitent with Dave's experience...
Peahead
Well-Known Member
I am bringing back this 9 month old thread because I have learned more about anodes and found a very good link to share. Edit - It was posted earlier in this thread by Foxsea post #19 but worth reposting !!!
Absolutely Wwunder, mixing anodes is NOT efficient ! I have experienced this too. A local yamaha dealer sold me mixed metal anodes accidently or was oblivious to them. At the time I installed them I didn't pay attention to their weights and was unaware at that time that they were different. They were both OEM yamaha parts but the skeg anode was zinc ( probably older stock) and the "handlebar" outboard bracket anode was aluminum. In use the aluminum anode was protecting my outboard but also protecting my zinc skeg anode! The result was that my aluminum anode was working harder and desinigrated quite quickly while the zinc anode being protected by the aluminum anode looked almost new after 8 months of full time moorage with my leg always kept down !!!
As I said I am bringing this thread back after 9 months because I am repacing some anodes today and recently read from this great link originally posted by Foxsea . I wanted to share this link again about aluminimum anodes and why they are highly recommended over zinc ( and magnesium) . Alot of other questions and confusion in the above posts are answered via the link to this metals company. They explain why zinc and magnesium can be poor choices for salt water applications and a simple explanation of how aluminum anodes protect aluminum legs and welded aluminum hulls.
YES YOU CAN USE ALUMINUM ANODES TO PROTECT ALUMINUM hulls and legs.
The site even goes to the extent of saying in some cases equipment warranties can be void if using zinc anodes instead of Aluminum and that in the early nineties outboard manufacturers began switching to aluminum anodes because zinc as an anode was proving to not be sufficient enough protection as many corriosion issues were appearing while using zinc. They suggest aluminum as the a safe anode to use in all applications (as long as it is not cheap poor quality and not to the published naval specs)
http://www.performancemetals.com/anodes/AnodeFAQs.shtml
Here's a quote from the site that your warranty could be void if using zinc anodes !!! ....and why in saltwater MAGNESIUM ANODES ARE NOT A GOOD CHOICE due to risk of "overprotection" - the site explains the problems "overprotection" can have:
"Initially the anodes for these units [outboards and sterndrives] were made of zinc, but in response to corrosion problems, Mercury and Johnson/Evinrude/OMC started selling the aluminum anodes in the early 1990’s. Other manufacturers are switching to aluminum too. The small increase in protective voltage helps ensure that the sterndrive is protected. If you use zinc anodes you may even invalidate your warranty! Again, be careful using magnesium anodes since you can overprotect your sterndrive or outboard "
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I'm still reading--a quote from that website--
Magnesium generates -1.6 Volts, i.e. negative 1.6 volts.
Aluminum sacrificial anode alloy generates -1.1Volts
Zinc, -1.05 Volts
In order to provide protection, the highest practicable voltage difference possible is required between the sacrificial anode and the metal to be protected
is causing me some confusion so I will go to the links and learn more- thanks again!
Magnesium generates -1.6 Volts, i.e. negative 1.6 volts.
Aluminum sacrificial anode alloy generates -1.1Volts
Zinc, -1.05 Volts
In order to provide protection, the highest practicable voltage difference possible is required between the sacrificial anode and the metal to be protected
is causing me some confusion so I will go to the links and learn more- thanks again!
Peahead
Well-Known Member
My understanding from my readings it that aluminum anodes protect aluminum hulls the same way aluminum anodes protect aluminum outboard legs and sterndrives. The aluminum anode is actually manufactured with other metals in it which allows it to be a succesful and efficient as a sacrifical anode protecting aluminum outboard and sterndrive legs and aluminum hulls. The aluminum of a hull and outboard is more noble than the aluminum anode so hence why it works.
Peahead
Well-Known Member
That will happen when both the zinc and aluminum anodes are installed (mixed) at the same time. The aluminum anodes were doing all the "sacrificing" (corroding) and protecting metals with more nobility such as the motor leg and the zinc anode itself..... hence the zinc anode in Dave's photo looking clean and intact.
Quote from my readings: "Aluminum alloy anode provides more protection than a zinc anode because it has a small increase in protective voltage [ -1.03V for zinc and -1.1V for Aluminum] . Aluminum is the only anode that is safe for all applications"
Desdemona1995
New Member
Reading this link compelled me to respond with more information on anode. One link that's attached above is from a company that only makes aluminum anodes and they're pushing these anodes for ALL bodies of water. While aluminum does perform well in salt water, there's drawbacks in certain cases and anode mfr's aren't either don't know or aren't sharing this info. As a leading mfr of zinc (ZN), aluminum (AL) and magnesium (MG) anodes, this year we are receiving a substantial increase of inquiries in wanting to switch from ZN to AL anodes. This has been induced partly by a couple anode mfrs pushing Aluminum. We take the stance of not pushing any type of them, but giving out information so customers can make an informed choice of protection.
AL anodes are being marketed as an anode that performs well in all situations, is cheaper, is lighter and lasts longer. Is there truth in this? Yes, and NO.
Al is more negative (electrochemically) than ZN by 50mv. In saltwater and upper levels of brackish waters "both" anodes will protect the basic metals that vessels use. In the lower brackish levels and fresh water, AL out performs Zn electrochemically. While ZN looses an edge here, it makes this up in the sloughing dept. Zn sloughs it's consumed metal much better than AL. Without sloughing, the consumed metal can film over and form a crust (barrier) which can cause passivation in the anode. The "partial" protection of ZN is then a welcomed advantage over the now reduced or inactive AL anode. Both of these anodes bow to magnesium (MG) anodes in freshwater. The high current output of MG is needed in the high resistivity fresh waters.
In salt water the same scenario can also occur. As a vessel increases in speed, corrosion rates are increased and anodes work harded. When the boat is moored, the anodes settle down (without a current demand on them) they can film over. This occurs when a vessel is moored and the longer it sits, the higher the chance of anode passivation. This however, occurs predominantly in AL anodes. When the vessel moves again, anodes react by once again putting out more current, therefore re-activating themselves. Cutting through the water also cleans any soft film off the anode, exposing new anode material to be consumed. The longer a vessel sits, the bigger the chance of filming over, followed by having a crust form. If a vessel remains active in salt water, both ZN and AL work. If a vessel sits for periods of time, it's at risk of loosing anode protection with AL.
While some claim never to use MG in saltwater, it works. The cautions are over-voltage because of the high voltage it puts out. If done correctly, there's no issues, however, Joe Boater likely doesn't know the in's n out's of cathodic protection, so beware. Another drawback is the lifespan of MG. Very short to ZN and AL, with AL lasting about 30% longer than ZN.
Bottom line: look at vessel habits before making a choice. If the vessel sits for periods of time, either use zinc anodes and / or do maintenance on the anodes, especially aluminum anodes which involves cleaning them.
On Aluminum hull vessels: Over-voltage is a concern. Both zinc and aluminum anodes have enough capacity to protect aluminum hulls which are generall made from alloy 5086 series. Installing excessive amounts of anodes likely will create a release of hydrogen from the metal's surface, which causes deep pitting. This over-voltage easily occurs with magnesium anodes high current output of nearly 50% high capacity and zinc and aluminum. Only use magnesium to protect aluminum if you know what your're doing.
Sometimes Magnesium is the correct choice, sometimes Aluminum, sometime Zinc. There's a place in corrosion protection for all three of these anode types, depending on the many variable factors.
AL anodes are being marketed as an anode that performs well in all situations, is cheaper, is lighter and lasts longer. Is there truth in this? Yes, and NO.
Al is more negative (electrochemically) than ZN by 50mv. In saltwater and upper levels of brackish waters "both" anodes will protect the basic metals that vessels use. In the lower brackish levels and fresh water, AL out performs Zn electrochemically. While ZN looses an edge here, it makes this up in the sloughing dept. Zn sloughs it's consumed metal much better than AL. Without sloughing, the consumed metal can film over and form a crust (barrier) which can cause passivation in the anode. The "partial" protection of ZN is then a welcomed advantage over the now reduced or inactive AL anode. Both of these anodes bow to magnesium (MG) anodes in freshwater. The high current output of MG is needed in the high resistivity fresh waters.
In salt water the same scenario can also occur. As a vessel increases in speed, corrosion rates are increased and anodes work harded. When the boat is moored, the anodes settle down (without a current demand on them) they can film over. This occurs when a vessel is moored and the longer it sits, the higher the chance of anode passivation. This however, occurs predominantly in AL anodes. When the vessel moves again, anodes react by once again putting out more current, therefore re-activating themselves. Cutting through the water also cleans any soft film off the anode, exposing new anode material to be consumed. The longer a vessel sits, the bigger the chance of filming over, followed by having a crust form. If a vessel remains active in salt water, both ZN and AL work. If a vessel sits for periods of time, it's at risk of loosing anode protection with AL.
While some claim never to use MG in saltwater, it works. The cautions are over-voltage because of the high voltage it puts out. If done correctly, there's no issues, however, Joe Boater likely doesn't know the in's n out's of cathodic protection, so beware. Another drawback is the lifespan of MG. Very short to ZN and AL, with AL lasting about 30% longer than ZN.
Bottom line: look at vessel habits before making a choice. If the vessel sits for periods of time, either use zinc anodes and / or do maintenance on the anodes, especially aluminum anodes which involves cleaning them.
On Aluminum hull vessels: Over-voltage is a concern. Both zinc and aluminum anodes have enough capacity to protect aluminum hulls which are generall made from alloy 5086 series. Installing excessive amounts of anodes likely will create a release of hydrogen from the metal's surface, which causes deep pitting. This over-voltage easily occurs with magnesium anodes high current output of nearly 50% high capacity and zinc and aluminum. Only use magnesium to protect aluminum if you know what your're doing.
Sometimes Magnesium is the correct choice, sometimes Aluminum, sometime Zinc. There's a place in corrosion protection for all three of these anode types, depending on the many variable factors.
Interesting; we were talking about this the other day. It would seem there is more profit in pushing Al because it is cheaper and you can change almost as much as zinc and is much lighter so shipping/handling charges from say China is also a factor. My uninformed opinion is that zinc protects better on my boat with a large Al pod and half submerged Al lift but the outboard manufactures really seem to be pushing AL anodes. I wonder if it has more to do with making more money than which is best in a given situation. I have tried them both and for my boat the zinc seems to get eaten faster than AL and I would assume therefore offer better protection.
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Desdemona1995
New Member
I have seen many passivated aluminum anodes from different mfrs and the general consensis is anodes that are in calm water situations, mainly with coated materials. What I mean by coated materials is this: The actual wetted surface area that need protection for bare piece of steel that's 10' x 10' is 100 square ft. If it's coated and has a few stratches and the coating is somewhat degridated, there may be 5' of steel that's exposed to seawater. The attatched anode now is protecting a much smaller area requireing less current, so the anode isn't as active. Under this situation, passivation can occur of the anodes are allowed to film over, so maintenace is required to keep them clean.
Which protects best? With steel and aluminum boats, both types of anodes provide enough current to protect it in saltwater. Al is slightly more negitive, which is a good thing, but once the vessel is at a stable point it's protected. Adding any extrta current does not protect it "better". Al will last longer, but that doesn't mean it's not working as hard. Looking at the "electrochemical" properties of each anode and the math is done, )Al and Zn equivalents of the same size, not weight), Al has an output that results in longer life. So in your case, Rockfish, don't assume the aluminum anode is not working as well, just because it's lasting longer.
Which protects best? With steel and aluminum boats, both types of anodes provide enough current to protect it in saltwater. Al is slightly more negitive, which is a good thing, but once the vessel is at a stable point it's protected. Adding any extrta current does not protect it "better". Al will last longer, but that doesn't mean it's not working as hard. Looking at the "electrochemical" properties of each anode and the math is done, )Al and Zn equivalents of the same size, not weight), Al has an output that results in longer life. So in your case, Rockfish, don't assume the aluminum anode is not working as well, just because it's lasting longer.
smokedvw
Active Member
Bringing this baby back from the dead.
I went to buy zincs today for my boat. 80's double eagle with a yamaha 150 and trim tabs. The boat sits at the marina all year on the inside area closest to a grassy field and main fresh water run off. I've noticed my hull and engine is way cleaner at this marina location compared to another spot with I'd assume a higher degree of saltwater and no run off.
I pulled it after 1.5 years. The anode above the prop and the bar below the engine are both fairly worn. I believe these are aluminum. The zinc ones on the trim tabs has 1 that needs replacing.
When I was there I was told about the aluminum and that's what everyone uses now. I thought maybe it's some environmental bs and also because they make more money on it.
Since this thread is 10 years old. I'm curious for those that Moore their boats how its gone for them? What also concerns me about aluminum is the film buildup that dies not slough off. I can leave my boat for up to a month without using it at certain time and I'm wondering if that will be too long?
Another question when you guys attach your trim tabs to the engine via wire are you hooking it to the rear bar or which location?
Thanks
I went to buy zincs today for my boat. 80's double eagle with a yamaha 150 and trim tabs. The boat sits at the marina all year on the inside area closest to a grassy field and main fresh water run off. I've noticed my hull and engine is way cleaner at this marina location compared to another spot with I'd assume a higher degree of saltwater and no run off.
I pulled it after 1.5 years. The anode above the prop and the bar below the engine are both fairly worn. I believe these are aluminum. The zinc ones on the trim tabs has 1 that needs replacing.
When I was there I was told about the aluminum and that's what everyone uses now. I thought maybe it's some environmental bs and also because they make more money on it.
Since this thread is 10 years old. I'm curious for those that Moore their boats how its gone for them? What also concerns me about aluminum is the film buildup that dies not slough off. I can leave my boat for up to a month without using it at certain time and I'm wondering if that will be too long?
Another question when you guys attach your trim tabs to the engine via wire are you hooking it to the rear bar or which location?
Thanks
BC Coast Pilot
Well-Known Member
It's mostly related to the density of water you are in.
Saltwater, use Zinc 100%
Pure freshwater us Magnesium
In brackish water which is any where inbetween and probably where you are at Aluminum is recommended and yes it is better for the environment.
Try the martyr website
Why Zinc-less?
martyranodes.com
zurk
Well-Known Member
ive always run 100% aluminum anodes. they work well. test it out with a multimeter when installing (one probe to anode one to protected surface i.e. hull) to ensure no overprotection ( > -950mV and < -1200mV ).
i use commercial aluminum anode bricks i cut into 4 pieces and use 1 piece at a time.
i use commercial aluminum anode bricks i cut into 4 pieces and use 1 piece at a time.
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