Electrolysis Issue on Center Console

[mbevins]

Finally getting around to putting my center console in the water. Better late than never I guess.
As I was prepping and cleaning I came what looks like an electrolysis problem. The swim platform is supported from 1" sq aluminum tubes. If you look at the picture you'll see the paint and the anti fouling is blown through and it looks like pitting on the surface. This is in the Great Lakes so it's freshwater.
I've owned the boat for about ten years and this is the first time something like this has shown up.
It's a straight i

nboard, technically I do keep shore power on the boat. I have a built in battery charger that I have plugged into a 15amp recpt on the dock.
The starboard side which is against the dock seems to be worse than the Port.

I'm thinking it might be an external issue, likely the boat on the other side of the dock.

Does anyone have any thoughts?

 

[Comodave]

Does it have sacrificial anodes?

 

[mbevins]

I was thinking about that. The shaft was changed last year and I see that the new one doesn't have an anode. There is one on the rudder, it appears to be well used up. I've put a new on and I'm trying to locate a shaft anode as well, but none in stock.

 

[Donna]

Electrical current is more likely at a marina and especially if you are next to a boat that does not keep up with maintenance. Check the grounding/bonding on the entire boat. Replace as necessary.

 

[foggysail]

My guess is that there is no bonding on that or those metals. I had a similar thing happen to my boat that I noticed before last season began. I replaced those that were badly corroded and bonded them on the inside of the transom.

 

[mbevins]

My guess is that there is no bonding on that or those metals. I had a similar thing happen to my boat that I noticed before last season began. I replaced those that were badly corroded and bonded them on the inside of the transom.

You're correct, there is no bonding on the boat at all.

 

[Ski in NC]

If you are not going to protect it with an anode, then don't paint it. Anodic activity will find flaws in the paint and concentrate corrosion in the flaws and create pinholes. Either zinc it or leave it bare metal.

 

[foggysail]

You're correct, there is no bonding on the boat at all.

If the mounting bolts are accessible from the inside of your boat and again "if" you can attach lugged wires to those bolts that hold the exterior mounting bracket, you might be able to find a nearby place to bond the wire.

Gees, very unusual for your boat not to have a bonding circuit but you know your boat better than I.

I use only one anode on my boat, a 6X12X1" aluminum divers plate mounted onto the transom. But that anode is attached to my boat's bonding circuit. Even so, my trim tabs although bonded inside of the hull, had a poor bond to the actual tabs themselves. So I ran short lengths of SS aircraft cable from the trim tabs to the mounting bolts that secure the aluminum anode. That resolved my problem.

Eliminated shaft anodes by using shaft brushes to keep them bonded or I would have required anodes on them. Shafts are poorly grounded/bonded because they attach to the engines by way of an oil bath in the transmissions.

 

[mbevins]

If you are not going to protect it with an anode, then don't paint it. Anodic activity will find flaws in the paint and concentrate corrosion in the flaws and create pinholes. Either zinc it or leave it bare metal.

I think this makes sense. I'll put an anode on each bracket plus reinstall one on the shaft.

 

[mbevins]

If the mounting bolts are accessible from the inside of your boat and again "if" you can attach lugged wires to those bolts that hold the exterior mounting bracket, you might be able to find a nearby place to bond the wire.

Gees, very unusual for your boat not to have a bonding circuit but you know your boat better than I.

I use only one anode on my boat, a 6X12X1" aluminum divers plate mounted onto the transom. But that anode is attached to my boat's bonding circuit. Even so, my trim tabs although bonded inside of the hull, had a poor bond to the actual tabs themselves. So I ran short lengths of SS aircraft cable from the trim tabs to the mounting bolts that secure the aluminum anode. That resolved my problem.

Eliminated shaft anodes by using shaft brushes to keep them bonded or I would have required anodes on them. Shafts are poorly grounded/bonded because they attach to the engines by way of an oil bath in the transmissions.

Being in Freshwater and not really having any shore power there has never been an issue in the past. The only thing that has changed was the shaft last year, and I suspect that because the mechanic didn't put the anode back on that might be the cause of this.

 

[foggysail]

Being in Freshwater and not really having any shore power there has never been an issue in the past. The only thing that has changed was the shaft last year, and I suspect that because the mechanic didn't put the anode back on that might be the cause of this.

I agree with you!!! Fresh water is a poor electrical conductor. That is what makes it dangerous if one is swimming in water where there is an electrical current. That danger is much less n salt water because of its conductivity.

 

[Art]

We also dock in fresh water.

I isolate all my batteries via Perko on/off switches. I also do not leave any shore power plugged in when we leave boat. And, I make sure that the boat is tied in slip so it touches nothing. It basically becomes an island with little to no electric current ever coming in contact. My boat's anodes deplete very slowly.

 

[Turner]

Hang a grounded zinc "fish" over the rail, just don't forget to pull it up go out in the boat. We are in a marina with quite a few livaboards around us, this zinc fish does the trick.

 

[Lou_tribal]

You wrote that your support is made of aluminium. If I am not totally wrong and out of understanding you should ensure to use magnesium anode and not aluminium if you add any anode.

L.

 

[mbevins]

You wrote that your support is made of aluminium. If I am not totally wrong and out of understanding you should ensure to use magnesium anode and not aluminium if you add any anode.

L.

Right you are. I added a magnesium anode to each support. Now I've got to check the dock area to see if it's me or the boat next to me causing the problem.

 

[boatpoker]

The most likely cause is your antifouling paint. I/O manufacturers will void the warranty if antifouling paint touches your i/o due the the metal compounds in many paints. It is quite common to create a galvanic cell between AF paint and aluminum with the aluminum becoming the sacrificial anode.Same thing applies to your aluminum struts. Do not paint and leave a 1.5" unpainted border around the mounting point on the transom. Do not take advice from anyone using the term electrolysis. Use of that word is a clear indication of lack of knowledge on this topic.

ABYC Certified Marine Corrosion Analyst.

 

[mbevins]

The most likely cause is your antifouling paint. I/O manufacturers will void the warranty if antifouling paint touches your i/o due the the metal compounds in many paints. It is quite common to create a galvanic cell between AF paint and aluminum with the aluminum becoming the sacrificial anode.Same thing applies to your aluminum struts. Do not paint and leave a 1.5" unpainted border around the mounting point on the transom. Do not take advice from anyone using the term electrolysis. Use of that word is a clear indication of lack of knowledge on this topic.

ABYC Certified Marine Corrosion Analyst.

Now you tell me right after I launched the bugger.
Seriously though.

So what your saying is that the paint that was on the bracket broke down somewhere allowing the antifouling that was on top to create this condition.

So what I did probably was create a bigger problem. I cleaned it up and applied a new coat of antifouling on the clear aluminum. I added a magnesium anode to each bracket as well.

Do I need to pull the boat or will the anodes save the bracket for the season?

 

[boatpoker]

Now you tell me right after I launched the bugger.
Seriously though.

So what your saying is that the paint that was on the bracket broke down somewhere allowing the antifouling that was on top to create this condition.

So what I did probably was create a bigger problem. I cleaned it up and applied a new coat of antifouling on the clear aluminum. I added a magnesium anode to each bracket as well.

Do I need to pull the boat or will the anodes save the bracket for the season?

The anodes may help as long as there is good continuity between the anode and the aluminum. i.e. less than 1ohm

 

[mbevins]

There should be, sanded the bracket clean then through bolted an anode 1"x3"x3" with a couple of 10-32 screws and nuts.

Must admit being in Freshwater I've never given these brackets much thought and until this year they've been trouble free.

 

[Lou_tribal]

There should be, sanded the bracket clean then through bolted an anode 1"x3"x3" with a couple of 10-32 screws and nuts.

Must admit being in Freshwater I've never given these brackets much thought and until this year they've been trouble free.

I did the same before splashing this year as the PO was just ignoring the anodes state. I cleaned up the brackets clear of any paint, bolt anodes and checked continuity with the ohm-meter. I would recommend to always do a check as may have some surprise. On one of my anode some paint chips remained stuck in the back and continuity was not good it is an easy check that allow to see if they are correctly installed or not.

L.