View Full Version : Electrolysis--

Frantically Relaxing
07-06-2015, 10:02 AM
First off, this first pic was taken in 2011---

The boat's been out a couple of weeks now. The hull has several thru holes surrounding corroded areas. Only one of the holes was the leak, the others opened up easily with my finger or the pressure washer.

The first 2 pics show the difference between March 2011 and now.

Note the circled areas, and some small spots down the length of the hull. These areas were just starting to show missing metal back then, very little, like .01" or so. I treated and primed painted these and a few other areas.

Also note the tracking fin, specifically that it's bottom edge is still all there...


this is now I've circled the same area I fixed in the first pic. Notice the bad area didn't spread out. None of the areas I fixed in '11 got larger. But they got deeper. And a whole slew of other areas have cropped up.


and compare the tracking fin, this pic is in the same area as the first pic...


--this pretty much explains the whole story: Rust didn't do this, this is purely an electrolysis issue. Rust is just a by-product...

Frantically Relaxing
07-06-2015, 10:03 AM
Pics start from the starboard rear, there's 4 holes in this pic, but barely visible.


This is the first 3 holes, back within the engine room (which was dry)


The 4th hole-


Frantically Relaxing
07-06-2015, 10:03 AM
Moving forward towards the bow-





Frantically Relaxing
07-06-2015, 10:04 AM


--The pic above is right below my steering wheel. There's also a non-visible pinhole farther right, that IS visible easy enough from inside the boat. I have some pics I need to download off my wife's phone (but she's using it at the moment ;) ) They're not very good, but they'll help explain that the phrase "steel boats rust from the inside out" doesn't apply to this boat. While I don't have much access to the bottom proper, I have nearly 4" between the edge wood floor and the sides. Enough room to weld from the inside if necessary...

I inspected the entire length of the starboard side, same as in the pics. And aside from the holes and all the daylight they let in, the hull looks brand new. There's not even a HINT of rust anywhere inside. Not even the edges of the holes are rusty. They look like they've been drilled thru and deburrred. No rust or soft spots anywhere outside either. All the bad spots on the outside pass the hammer test.

I'm no expert by any means, but it appears to me that my missing steel was not caused by or is rust cancer. Rust just seems to be the byproduct of the severe electrolysis.

I haven't had time to fully inspect the bottom, although a little surface rust is showing thru in many places....

SO-- what are my options? (other than finding and fixing a severe electric issue with my AC power)...

Frantically Relaxing
07-06-2015, 10:34 AM
Got a couple of pics off the wife's phone--

From my door in the floor (pardon the mess, moving weight out to help the crane was a bit frantic)...
the pinhole I mentioned is visible at the left...


And this is the only halfway good pic that shows the hull from the inside. No rust whatsoever, just holes.
The entire length of the starboard side looks exactly like this.


07-06-2015, 12:55 PM
Ugh. I feel your pain. I am in an aluminum boat and corrosion is a constant worry with me and my boat. My kingscraft didn't have any pin holes but another season without fixing the issue and she would have had it.

I only know a bit about Aluminum boats so that is what I will base my response off of.

1. Annodes
-Do you have any on the boat anywhere?
-If you do, what state are they in?
2. Electrical
-Do you have a galvonic isolator or an isolation transformer?
-You would need to check your hull potential in the water so we can do that now but a reference electrode would be a great tool to have. boatzincs.com

I don't have anything to help on repair options. Unfortunately, I believe that insurance doesn't cover issues from Galvonic corrosion.

Frantically Relaxing
07-06-2015, 03:38 PM
this is the only pic from out back--


I have the hull anodes circled, however, and I'm feeling pretty dumb after checking them closely last weekend, I believe they're just anode mounting plates--

Because I had to put the boat against the dike for the crane, I knew I was going to lose the port prop. I also lost the trim tab anode above it. But the one on the SB prop is still there, and it's in better shape than the prop is. The drive housings are pretty bad. The rams are REALLY bad. The anodes under the drives at the transom are somewhat corroded, but not all that bad. The only anode that looks like it should is one of the drive-to-transom mounting nut covers, it almost looks like someone took a welding torch to it.

As for galvanic isolators and transformers-- I WILL be getting an isolation transformer before this boat ever goes back into the water. I've known about GI's, just too bad they've never been high on my priorities list. Never heard of an isolation transformer until 2 weeks ago. Just hate learning things the hard way.

But I may get some local help with this finally. My 'welder guy' who helped me build the trailer for this boat hasn't returned my calls (yet). But one of my customers stopped by today, needing some work for his son's race car. He's going to put me in touch with the guys who do all their welding, hopefully I'll get some options and real world price guesstimates..

07-06-2015, 05:27 PM
I believe you have a SEVERE STRAY CURRENT problem. Your boat or some one near you or your dock is leaking DC and it ate your boat. Your boat should be equipped with substantial anodes fore, aft and on the keel. My 55 Pluckebaum had 3 footers foreward a 3footer on the keel 2 1 footers on the transome and 4" round on the rudders as well as the round ones on the shafts. Also had an Isolation transformer.

After you replace the bottom plating I would STRONGLY suggest 2 or 3 coats of COAL TAR EPOXY.

For sure you have to identify the source of the stray current thats eating your boat.

You may be interested in the following:


Turn your insurance claim siteing Stray Current Corrosion, not Galvanic Corrosion. 2 different animals.


07-06-2015, 07:37 PM
Is the corrosion all over or mainly one side? If contained to one side I would start looking at the boats on that side of you for the stray current.

07-07-2015, 06:55 AM
Are your anodes made of magnesium or zinc? Magnesium is necessary for fresh water while zinc or aluminum typically only work in salt.

It's amazing your boat was still floating with all this mess!

07-07-2015, 07:44 PM
If the picture of the transom shoews the size of the anode it was window dressing. You need a LOT more than that little bitty thing. All that being said you could have had a ton of anodes and your boat would have still been eaten alive. You will need a GOOD marine electrician to sort this one out.

07-08-2015, 08:40 PM
The difference between Galvanic and stray Current corrosion is discussed in this article.


07-09-2015, 08:27 PM
Good article. I have one on my website too. http://newboatbuilders.com/pages/corrosion.html

Frantically Relaxing
07-14-2015, 03:42 PM
As for good articles about this stuff, I found and read this page last night:


-- The way it's written was very easy for me to make sense of electricity in general, I really learned a lot from it!

One issue that was reinforced was the fact that I do have an AC issue since I can't plug the boat into a GFI without tripping it. Another issue is that yes, DC rather than AC power caused my problems...

So what I did was think real hard about what exactly could be causing a DC power leak? My bilge pump is not automatic, so it's never powered up. I don't have any wires dangling in the bilge, which is bone dry btw, I haven't added any DC options. I HAVE been trying different electric fuel pumps on the generator lately, but I know the hot is connected right, and it's not hot anyway unless I'm running the genny, which I hardly do...

Then last night it dawned on me....


I'll bet a buck my solar panel killed my boat... it's mostly unused since the power it makes-- 27 volts IIRC- never makes it to the batteries because the charge controller is bad. But it's never been disconnected. Sadly, I've never given it much thought. The wires are connected with twisties, and I'm not even sure they're both there now (these pics are 2 years old). Even if they are, the wires may be squished between the slide and bracket and rubbed bare. Either way, I have plenty of DC power within mm's of the metal mounting bracket...


To look at where the mounting bolts are, the upper hinge bracket doesn't appear to be connected to my railing...


But I only have the pics to go by for now. The lower folding hinge is connected to plenty of metal, but it's insulated from the upper hinge. But if the upper bracket is bonded to or is connected to my metal railing in any way, I think I've found my answer...

-- and the slide is mounted to far starboard, right next to this, which is the worst corrosion by far anywhere on the SIDE of the boat....


It does make sense...

03-08-2016, 06:55 AM
Have you had any luck tracking this down?

Frantically Relaxing
03-17-2016, 09:53 PM
Haven't done much with it during the winter, but I need to GET it tracked down. With the boat on blocks, I've measured 440mA DC from the hull to a ground rod. (I just noticed the ground rod is visible in the first pic, in the gravel area below the drive) And the batteries are still connected... I shot some rust converter over all the exposed metal before winter. Everywhere I sprayed looks pretty much the same except here on the starboard rear around those holes (the worst part of the boat, same area as the last picture above). That white powdery crust doesn't happen during simple oxidation, pretty sure that's electricity still at work.



03-18-2016, 06:33 AM
Here is what I would do. Have someone keep the volt meter in hand doing a constant measurement. I assume you have multiple batteries. One at a time disconnect each battery and check the reading. Determine which battery looks to have the issue attached to it and trace back all the leads. If this battery is what feeds your house DC panel, monitor the voltmeter as you pull each 12v fuse. If the reading goes down for a specific device, trace out the wires and see what device it is.

03-19-2016, 03:54 PM
Some how you are getting current on the hull. You need to eliminate that. JT's suggestion is a good way to track it down. It could be as simple as a piece of equipment that has a metal enclosure touching the hull. Or it could be someone actually ran a ground wire to the hull (bad). There are other scenarios, but you are not going to stop this corrosion until you find it. Frankly I would suspect the engine/sterndrives but it's better to trace it down.

03-20-2016, 08:16 AM
Zinc also work in fresh, however you need more of them. Mag anodes are a more recent product.

Frantically Relaxing
03-26-2016, 01:02 PM
"Agreed" and "I know!" to all the above! :)

Also of note about this, is that there's evidence this problem was a problem before we bought the boat in '06. In this pic, taken at Lake Powell the weekend we removed everything up top so it could be towed, notice the rust at the lower rear corner, and all down the sharp lower edge of the hull. That's exactly where all the bad spots on the port side are now. And there's no indication that any of this rust or the corrosion that's present on the port side ever began via simple oxidation. This boat's had an electrical leak forever.


--on the starboard side, the hull IS rusting from the inside-out, due to some oil absorbers I didn't know were there, that trapped water along the hull edge. There, and 2 thru-hulls on the starboard side are the only places I've found on the entire hull with rust started by oxidation...

05-11-2016, 07:32 AM
What is the latest on this?

Frantically Relaxing
05-22-2016, 01:27 PM
The latest is, due to my engraving business keeping me working 17 hours a day, and continually crappy weather- not WINTER weather or DURING the winter when we could use the snow to fill up our empty lake-- has been hindering my repair efforts, so not much has been happening yet.

I have found that while there's much pitting in some areas, and a little pitting in quite a few areas, aside from the engine room issue noted above, I've found only one small area about 4" x 6", on the bottom but near the edge, that could be considered a 'structural' issue. There are several small holes, most average less than 1/8" diameter. There's 2 holes I can almost fit my pinky finger in, and maybe a half dozen holes half that size. The rest, and all holes on the bottom proper, are essentially pinholes. The "fins" under the boat near the edges (which are actually seams in the steel construction), due to being the path of least electrical resistance, got brunt of the damage. Fortunately. :)

As for the electric issue that caused the problem, I haven't had the time to delve into that. Since it's a DC voltage issue, I don't think it'll be all that hard to track down. I can almost guarantee the problem lies somewhere under the lower helm:


I didn't do it!!! That's the result of 3 previous owner's installing stereos, marine radios, cellphones and all the antenna's they require, plus who knows what else. I've since removed all the cellphone wiring, which was substantial. But that was 5 years ago. If ANY ground under there is in contact with ANY hot, regardless of how minimal the contact, it would cause the damage. I've read where 1 volt of DC power can eat an entire aluminum I/O drive within a month, so it doesn't take much...

More to come! :)