Anodes

slab tech 1

Works overrated- lets go fishing
Apr 1, 2011
99
74
18
Ferndale
Name
Eric
Boat
Parker 2520 XL
I have been using aluminum anodes all around for the last two years. I was told they last longer and are good in the salt and freshwater. Most of the anodes seem to last quite a while (1 plus year) but the ones on my trim tabs seem to only last about 6 months. I assume this is because they are on stainless steel? They crumble apart. I pull my boat out and trailer home typically unless I plan on fishing every couple of days then I leave on the dock. Is zinc better than aluminum? Would I have stray current possibly even though it’s not affecting the outboard zincs?
 
Last edited:

tacklejacked

Capt./ Ho if I get to drive
Jun 2, 2009
2,584
2,407
113
Seabeck
Name
Greg
Boat
22 Hewescraft Searunner ET HT

This is a good read.

I just stick with zinc.. seems to work good for me on my tin boat.
 

tacklejacked

Capt./ Ho if I get to drive
Jun 2, 2009
2,584
2,407
113
Seabeck
Name
Greg
Boat
22 Hewescraft Searunner ET HT
And that's pretty fast to burn up zinc's in 6 months.. something is hot on your boat. IMO
 

Omakase

Well-Known "Member"
Apr 19, 2009
742
713
93
Kitsap
www.facebook.com
Name
Bob
Boat
24 LaConner
What kind of boat, aluminum or fiberglass? If aluminum hull then keep using aluminum on your trim tabs, hull and outboard. The stainless tabs are kept in check from attacking your hull by the aluminum anodes you are using. If you switch to zinc the tabs will focus more of their galvanic potential against your hull and the hull anodes. If you have a fiberglass hull switching your tab anodes to zinc will be ok.
 

Odin7

Doug Fir
Apr 19, 2008
1,483
1,230
113
Beverly Hills
Name
Elizabeth Warning
Boat
Space Shuttle
My last two boats were glass so I never gave much thought to protecting the hull.

I've been running my Aluminum boat in salt water for the past three years. Is there a particular place on the hull of aluminum boats that gets attacked first?
 

Omakase

Well-Known "Member"
Apr 19, 2009
742
713
93
Kitsap
www.facebook.com
Name
Bob
Boat
24 LaConner
Fiberglass boats don't need hull protection. Aluminum hulls should be equipped with a sacrificial anode, typically on the transom and made of mil spec aluminum which is alloyed to be slightly more reactive than zinc meaning that it will be more protective of your hull than zinc anodes. Aluminum boats that are most susceptible to galvanic corrosion are those with chine extrusions and other non-marine grade alloy components used below the waterline. Those are the areas that pitting will show up first if anodes are not used or are made of zinc. Stainless trim tabs attached directly to hull structure can also cause hull pitting if aluminum hull anodes are not used.
 
Last edited:

sgwill122

I've posted enough I should edit this section
Feb 21, 2011
1,685
1,748
113
Redmond/WA/USA
Name
Stephen
Boat
'Lady Karen' 28 Duckworth Offshore

This is a good read.

I just stick with zinc.. seems to work good for me on my tin boat.
Hey Greg do you notice any wear on your Zinc's? You might want to replace them with aluminum anodes as your outboard anodes will probably burn up a lot faster. From what I understand all outboards come with Aluminum anodes and being more reactive than zinc will go first. I did not know anything about aluminum anodes till I read a bunch of Bob's threads @Omakase . My boat came with big welded zinc anodes that I cut off and replaced with aluminum. Mine now show quite a bit of wear even though she is a trailer queen.
 

slab tech 1

Works overrated- lets go fishing
Apr 1, 2011
99
74
18
Ferndale
Name
Eric
Boat
Parker 2520 XL
My boat is fiberglass. Parker 2520 with offshore bracket that is aluminum. The Yamaha anodes are aluminum and they are mounted on similar metal which is why they last several years, but the tabs are not aluminum and I’m assuming that’s why they go quicker. But I have read that you don’t want to use zinc and aluminum. So I was wondering if anyone uses zinc on their outboards instead of aluminum? The offshore bracket also has aluminum anode on it. I suppose it’s doing it’s job anyways and that the tabs react quicker due to the dissimilar materials.
 

LeeMajors

Member
May 20, 2014
259
216
43
Washington
Name
Lee
Boat
40' Tiara 35 Open
I have been using aluminum anodes all around for the last two years. I was told they last longer and are good in the salt and freshwater. Most of the anodes seem to last quite a while (1 plus year) but the ones on my trim tabs seem to only last about 6 months. I assume this is because they are on stainless steel? They crumble apart. I pull my boat out and trailer home typically unless I plan on fishing every couple of days then I leave on the dock. Is zinc better than aluminum? Would I have stray current possibly even though it’s not affecting the outboard zincs?
On my Striper the trim tab anodes always burned the fastest. I preferred that because they were the cheapest and easiest ones to replace.

That said, did I read that correctly that they are burning that quick and you're not moored? If so, you probably have stray current somewhere. Check your wiring and install a galvanic isolater.
 

tacklejacked

Capt./ Ho if I get to drive
Jun 2, 2009
2,584
2,407
113
Seabeck
Name
Greg
Boat
22 Hewescraft Searunner ET HT
Hey Greg do you notice any wear on your Zinc's? You might want to replace them with aluminum anodes as your outboard anodes will probably burn up a lot faster. From what I understand all outboards come with Aluminum anodes and being more reactive than zinc will go first. I did not know anything about aluminum anodes till I read a bunch of Bob's threads @Omakase . My boat came with big welded zinc anodes that I cut off and replaced with aluminum. Mine now show quite a bit of wear even though she is a trailer queen.
No more wear than aluminum really. But I'm a trailer queen to. So in short .do whatever Bob says cause he's the man when it comes to this stuff.
 

slab tech 1

Works overrated- lets go fishing
Apr 1, 2011
99
74
18
Ferndale
Name
Eric
Boat
Parker 2520 XL
On my Striper the trim tab anodes always burned the fastest. I preferred that because they were the cheapest and easiest ones to replace.

That said, did I read that correctly that they are burning that quick and you're not moored? If so, you probably have stray current somewhere. Check your wiring and install a galvanic isolater.
Yes they get replaced probably 2x a year. Usually once now and again in July. I do keep my boat in the water usually for a few months in winter, then out, then back in for shrimp and Hali, then back out, then July for a month then out except random weekends. But the outboards and transom pod do not degrade at all comparatively. I have looked over and at all my wiring and cleaned all grounds or replaced if needed, but does seem like the trim tab anodes will degrade even on the trailer over time and leave a chalky white residue on the tabs.
 

Omakase

Well-Known "Member"
Apr 19, 2009
742
713
93
Kitsap
www.facebook.com
Name
Bob
Boat
24 LaConner
These anode discussions can get sideways pretty quickly because there are lots of different boat set-ups. Just to focus for a second on stainless trim tabs, if they are bolted onto an aluminum boat they will want to eat your boat. The normal defense is to put some anodes on your hull that will sacrifice themselves when the trim tabs come looking for dinner. So the question is, what kind of anodes should I use, zinc or aluminum?

There is one other important consideration when deciding what kind of anode you are going to put on your aluminum hull. If you have outboard motors the anodes that the factory installs on them when they are new and recommend they be replaced with when they are used up are aluminum. The reason for this is the sensitive aluminum castings in outboard motors aren't protected very well by zinc replacement anodes, motors start having problems when owners start using zinc anodes like seizing bolts, stuck and pitted parts, peeling paint, etc.

Bottom line, your outboard motors should only be equipped with aluminum anodes. So what does that have to do with hull anode choice? Well, on an aluminum boat the engine and its anodes are mechanically bonded to the hull and its anodes and both of those are also bonded to all the high nobility underwater metals on the boat such as SS props, motor shafts, trim tabs, nuts & bolts, etc.

So in that situation since everything is bonded together all the high nobility metals start looking for dinner as soon as the boat is dropped into salt water. If the boat has zinc anodes on the hull but aluminum anodes on the engine the engine anodes will get all the attention and will require frequent replacement meanwhile the zinc anodes on the hull being of slightly higher nobility than the aluminum anodes on the engine will basically contribute very little effort to protecting the boat hull (that is until the engine anodes are totally shot and the zinc anodes finally step up and do something). Keep in mind that the engine anodes are designed to just protect the engine they are attached to, no way are they able to properly protect an entire aluminum boat even if they are still in good shape.

So, the decision is obvious, if you don't want to overwork or prematurely wipe out your engine protection use the same kind of anodes on your hull that you have on your engines (mil-spec aluminum)so you have balanced protection.

And finally, getting back to the trim tabs on this hypothetical tin boat, you can keep their aggressiveness at bay by giving them their own set of anodes (again, aluminum) to chew on. Remember, on an aluminum boat keep all the anodes the same material as what is used on the motor, aluminum. They will all wear at the same rate and relatively slowly.

BTW, everyone likes to point to "hot marinas" when something strange is going on like suspected stray current corrosion but most problems are actually, ultimately confined to the boat with the issues.
 
Last edited:

Omakase

Well-Known "Member"
Apr 19, 2009
742
713
93
Kitsap
www.facebook.com
Name
Bob
Boat
24 LaConner
Now in the case of a glass boat with stainless tabs, an aluminum offshore bracket and an outboard motor you would want the motor to be equipped with the normal aluminum anodes and the offshore bracket to be equipped with an aluminum anode because it is bolted up and bonded to the motor but the stainless tabs could be left bare or equipped with zinc anodes (or aluminum anodes) because they are not connected to the engine package so a galvanic corrosion cell does not exist between those items. The tabs are on their own and not able to cause anyone any trouble. Now if you paint those tabs with copper bottom paint now you have a galvanic cell and you should install zinc anodes on bare spots on the tabs otherwise corrosion pitting in the tabs can get started.
 
Last edited:

liltrouble

Well-Known "Member"
Jun 9, 2012
410
457
63
ShillCreek, WA USA
Name
Shari
Boat
Mr. Buttercup
Probably going to see governmental intervention soon on the zinc anodes. The cadmium in the zinc is going to be the driver on that.
 

G-Spot

Captain
Mar 14, 2008
4,316
1,437
113
Salem/OR/USA
Name
John
Boat
53’ Hatteras STEEL N TIME
These anode discussions can get sideways pretty quickly because there are lots of different boat set-ups. Just to focus for a second on stainless trim tabs, if they are bolted onto an aluminum boat they will want to eat your boat. The normal defense is to put some anodes on your hull that will sacrifice themselves when the trim tabs come looking for dinner. So the question is, what kind of anodes should I use, zinc or aluminum?

There is one other important consideration when deciding what kind of anode you are going to put on your aluminum hull. If you have outboard motors the anodes that the factory installs on them when they are new and recommend they be replaced with when they are used up are aluminum. The reason for this is the sensitive aluminum castings in outboard motors aren't protected very well by zinc replacement anodes, motors start having problems when owners start using zinc anodes like seizing bolts, stuck and pitted parts, peeling paint, etc.

Bottom line, your outboard motors should only be equipped with aluminum anodes. So what does that have to do with hull anode choice? Well, on an aluminum boat the engine and its anodes are mechanically bonded to the hull and its anodes and both of those are also bonded to all the high nobility underwater metals on the boat such as SS props, motor shafts, trim tabs, nuts & bolts, etc.

So in that situation since everything is bonded together all the high nobility metals start looking for dinner as soon as the boat is dropped into salt water. If the boat has zinc anodes on the hull but aluminum anodes on the engine the engine anodes will get all the attention and will require frequent replacement meanwhile the zinc anodes on the hull being of slightly higher nobility than the aluminum anodes on the engine will basically contribute very little effort to protecting the boat hull (that is until the engine anodes are totally shot and the zinc anodes finally step up and do something). Keep in mind that the engine anodes are designed to just protect the engine they are attached to, no way are they able to properly protect an entire aluminum boat even if they are still in good shape.

So, the decision is obvious, if you don't want to overwork or prematurely wipe out your engine protection use the same kind of anodes on your hull that you have on your engines (mil-spec aluminum)so you have balanced protection.

And finally, getting back to the trim tabs on this hypothetical tin boat, you can keep their aggressiveness at bay by giving them their own set of anodes (again, aluminum) to chew on. Remember, on an aluminum boat keep all the anodes the same material as what is used on the motor, aluminum. They will all wear at the same rate and relatively slowly.

BTW, everyone likes to point to "hot marinas" when something strange is going on like suspected stray current corrosion but most problems are confined to the boat in question.
Bob
You discuss aluminum boats, but I think the OP was about anodes on a fiberglass boat. I would like your thoughts as well on the glass boats and which anode to use.... I always used zinc, because it has always been that “you change your zincs”...... until last year I was reading an article that actually suggested Aluminum anodes even on a fiberglass boat are better. I switched to the aluminum anodes. They last twice as long, they are Supposed to be good for salt and brackish water, and they are better for the overall health of the harbor/ocean.

You suggest in your post that zinc is superior to aluminum and therefore that is why you use aluminum and aluminum gets attacked first and then zinc, but the literature suggest the aluminum lasts longer than zincs which would suggest the aluminum alloy used for anodes may be superior to zinc?
 

Omakase

Well-Known "Member"
Apr 19, 2009
742
713
93
Kitsap
www.facebook.com
Name
Bob
Boat
24 LaConner
Bob
You discuss aluminum boats, but I think the OP was about anodes on a fiberglass boat. I would like your thoughts as well on the glass boats and which anode to use.... I always used zinc, because it has always been that “you change your zincs”...... until last year I was reading an article that actually suggested Aluminum anodes even on a fiberglass boat are better. I switched to the aluminum anodes. They last twice as long, they are Supposed to be good for salt and brackish water, and they are better for the overall health of the harbor/ocean.

You suggest in your post that zinc is superior to aluminum and therefore that is why you use aluminum and aluminum gets attacked first and then zinc, but the literature suggest the aluminum lasts longer than zincs which would suggest the aluminum alloy used for anodes may be superior to zinc?
Everyone says "zincs" because until recently that was the only metal that anodes were made of since the beginning of the battle against galvanic corrosion and since most underwater boat parts have been bronze and steel for most of that time zinc has served the purpose and will continue to do so for the time being.

BTW I don't see anywhere in my posts a suggestion that zinc is superior to aluminum, I actually feel quite the opposite. Aluminum is superior to zinc particularly in situations where zinc doesn't do the job properly. Aluminum is also less polluting and it is likely that at some point zinc anodes will be legislated out of existence.

As far as the ad literature stating that aluminum lasts longer that is very misleading and my only major beef with the aluminum anode manufacturers. If you read the fine print you'll see that what they are really saying is that pound for pound aluminum anodes last longer. However, when comparing two equal size anodes in the same service, one being aluminum and one being zinc the zinc anode lasts far longer but if the zinc doesn't protect what you want to protect then it doesn't matter, zinc is a bad choice no matter how long it might last.

As far as what anodes to use on a glass boat, assuming you are talking an outboard boat, use aluminum anodes on the motor. Granted, lots of older 2 strokes came with zinc anodes from the factory and anyone who has wrenched on older engines will agree that any of them that have spent much time in salt water can be horrible to work on because the factory anodes didn't prevent the castings and hardware from seizing up very well which required everyone to become experts at broken bolt removal. Practically all the motor manufacturers equip their engines with aluminum anodes now. You can buy aftermarket anodes for modern outboards made out of zinc but I strongly advise against using them. They never wear out which is why some people seem to like them but they don't properly protect the engines. They are not reactive enough and they don't work. The companies that make them should be horse whipped.

If your glass boat is an inboard/outboard use aluminum anodes on your outdrive. Your drive will be better protected. Yes you can find lots of zinc outdrive anode kits, aluminum better for the drive IMO.

If your glass boat is a straight inboard with a wired bonding system throughout to your through hulls, strut, rudder, etc. with a big anode on the transom traditional zinc is still a good choice but lots of boaters are switching to aluminum for the environmental reasons.
 
Last edited:
  • Like
Reactions: G-Spot and NW Dex

G-Spot

Captain
Mar 14, 2008
4,316
1,437
113
Salem/OR/USA
Name
John
Boat
53’ Hatteras STEEL N TIME
Everyone says "zincs" because until recently that was the only metal that anodes were made of since the beginning of the battle against galvanic corrosion and since most underwater boat parts have been bronze and steel for most of that time zinc has served the purpose and will continue to do so for the time being.

BTW I don't see anywhere in my posts a suggestion that zinc is superior to aluminum, I actually feel quite the opposite. Aluminum is superior to zinc particularly in situations where zinc doesn't do the job properly. Aluminum is also less polluting and it is likely that at some point zinc anodes will be legislated out of existence.

As far as the ad literature stating that aluminum lasts longer that is very misleading and my only major beef with the aluminum anode manufacturers. If you read the fine print you'll see that what they are really saying is that pound for pound aluminum anodes last longer. However, when comparing two equal size anodes in the same service, one being aluminum and one being zinc the zinc anode lasts far longer but if the zinc doesn't protect what you want to protect then it doesn't matter, zinc is a bad choice no matter how long it might last.

As far as what anodes to use on a glass boat, assuming you are talking an outboard boat, use aluminum anodes on the motor. Granted, lots of older 2 strokes came with zinc anodes from the factory and anyone who has wrenched on older engines will agree that any of them that have spent much time in salt water can be horrible to work on because the factory anodes didn't prevent the castings and hardware from seizing up very well which required everyone to become experts at broken bolt removal. Practically all the motor manufacturers equip their engines with aluminum anodes now. You can buy aftermarket anodes for modern outboards made out of zinc but I strongly advise against using them. They never wear out which is why some people seem to like them but they don't properly protect the engines. They are not reactive enough and they don't work. The companies that make them should be horse whipped.

If your glass boat is an inboard/outboard use aluminum anodes on your outdrive. Your drive will be better protected. Yes you can find lots of zinc outdrive anode kits, aluminum better for the drive IMO.

If your glass boat is a straight inboard with a wired bonding system throughout to your through hulls, strut, rudder, etc. with a big anode on the transom traditional zinc is still a good choice but lots of boaters are switching to aluminum for the environmental reasons.
thank you! The “zinc being superior to aluminum” statement was only referring to your post where you said it would attack aluminum first and then zinc since zinc was the stronger. Was meaning you felt it was superior in all applications.

you nailed it for me... I didn’t realize the lasts twice as long was based on pound for pound comparison.... That’s good info! Thanks!

Sounds like if I will need to go double thick on the aluminum to get similar time...