Electrolysis on Pacific Skiff 22 DV

[flyingfisherman]

First time poster. I've been the happy second owner of a 1999 Pacific Skiff DV. I don't believe this specific model is currently in production. Long story short, the boat has always been kept on a trailer or stored on a lift at my house since I purchased it from the original owner in 2003. This past week while the boat was being serviced it was discovered that electrolysis had occurred on several spots on the aft end of the boat along the center keel running four feet forward from the aft end of the boat. When checked with a probing awl it was discovered that the electrolysis had penetrated completely thru the hull and approximately 50 gallons of water ran out. The water smelled like sulfur and it was also not visible from the round inspection plate located in the transom of the boat. We've attempted a temporary fix with brass plugs covered with Teflon tape and sealant prior to arranging for an aluminum plate to be welded over the area in the fall as a long term have a situation that repair. My question concerns what might have caused the electrolysis to occur. The boat has never been bottom painted and with the exception of two 0ne-week long trips per year for the past 12 years this boat has never spent an entire day in the water. The trips were always to the same fishing location at a private pier and the boat was never connected to shore power. I'm trying to discern how the electrolysis happened so that I don't repeat the same mistake again. Is it essential to bottom paint these boats if 99 % of its life is spent stored out of the water? Also water inside of the boat that drained out when the electrolysis areas were punctured had to come from somewhere and I'm at a loss as to how the water got into the other compartments of the boat, any suggestions? At this point we're surmising that the electrolysis is starting on the outside of the hull and working in rather than originating from the inner surface of the hull and working out. Would this be an accurate assessment? The aluminum that came out of the three holes that went completely thru the hull were black oxidation in color. Lastly, when I purchased the boat from the original owner in approximately 2004 there was a small stainless plug in the extreme aft end of the boat where the transom meets the hull, I had always understood that dissimilar metals shouldn't be used this way and I'm curious if this would be indicative of a cause of the electrolysis problem or perhaps an indication of an earlier stray current issue that may have eaten away the original drain plug that may have been there. I'm hoping that someone with more expertise and knowledge than my friends and I can offer some suggestions to solving my dilemma and long term fix for the problem. I love the boat but I am seriously concerned that I have an issue that will result in a completely compromised hull.

[capesteve]

Others have reported similar problems with corrosion in areas where the hull was in prolonged contact with trailer bunks, which often are made of pressure treated lumber. Not sure if this would apply to your situation. Doesn't seem likey that the bilge drain plug would be related. Can you post pictures?

[kmorin]

fly'fish'
You'd best not put that boat back in salt water with brass plug taped or not... you're making one serious battery and will loose and perhaps flood your boat. Whoever suggested that is short any understanding of the galvanic table!!!

Cheers,
Kevin Morin
Kenai, AK

[flyingfisherman]

The boat will be back in my possession this evening, I will post pix tomorrow. Interesting suggestion regarding the bunks, my lift has pressure treated lumber bunks and small pads front and rear along the center line of the boat. The pads aren't in contact with the boat but the rear pad is directly in line with the electrolysis holes that are in the exact last 4 feet of the center line keel of the boat. Thanks for the help.

[kmorin]

Fly'fish'

Were your aware that the impregnation solution for pressure treated lumber is a copper solution? If the lift comes out of the water wet, and has the wt. of boat on a keel/hull centerline piece that means: salt water + copper+ aluminum= a several volt battery. Most people cover the raw wood with 'bunk covers' to get a ridged plastic material in contact with the aluminum to #1 allow drainage, and #2 to allow inert plastic to be supporting the metal hull.

I'd say the keel or centerline of the boat could trap salt water on the copper infused plank and make the problem you've described.

Seems like you may have found the problem?? are the holes that show, which were plugged, conic from the outside or tiny pin holes that could be conic inside? That will go quite a ways toward explaining the source of your corrosion? Likely the problem began where the holes are largest and worked/corroded through to the small (pin hole) side.

Brass is not even a temporary fix, little SS plugs, while still dissimilar metals would be better, 316L and passivated. Brass will (from the heads and base inside the bilge) create a ring around each fitting site that will begin to really get aggressively corroded.

Cheers,
Kevin

[welderbob]

I just saw the same problem on a similarly constructed boat. The corrosion was from the inside. The boat was trailered on a roller style trailer so wooden bunks was not an issue. The boat is ten years old and has 560 hrs on it original engine. There is very little access to the inside of the boat.What little I could see showed a lot of corrosion with some deep pitting. There was 10 -1/2" holes at the keel in the last 4 foot of the boat. The customer was very upset and looking for a way out of the boat. We reassured him that this was not a usual thing for an aluminum boat and that it could be fixed and could still live a very long life.

We ground out the holes and welded them closed. We than bent a strip of 5086 to the shape of the hull and continuous welded it to the boat. The repair took a little more than 2 hours. (we removed the boat from the trailer to make life easier .)

A pilot friend recommended that we looked as spraying the inside of the boat with "CORROSION- X ". He said they spray the inside of airplanes with the stuff. He recommend that I look for a applicator/ supplier at my local airport.

So from the Corrosion X website I found a local supplier, very nice guy,his shop was just a few miles from my shop. He said "I stop by within the hour to take a look". He came a looked, he said that he had seen planes that looked like our customers boat. He said he had been using Corrosion X on planes for 20 years and it works. He said the whole job could be done with a gallon of the stuff. He offered to loan me a long wand that would spray to spots you normal can't access.

I explained this all to the customer, he agreed to try this at the end of the season when we can get everything dry and to give the corrosion x time to dry. . A little moreresearch is needed, but it sound like a feasible solution.
Welderbob

[kmorin]

welderbob,
Have to say after reading the Corrosion-X website that this stuff looks like it should be in the under deck area of every welded boat? I'd not heard of it before your post, but, from what I read- looks like the armed services use it on their aluminum equipment.

Thanks for posting, the client's boat you mention sounds like bilge water was allowed to stand aft and form the pits you describe. I didn't learn from the OP if his holes came for inside, or were grown from the outside in? I think this C-X would work in the bilges or under deck if his holes did come from acidic/corrosive bilge water?

cheers,
Kevin Morin
Kenai, AK

[welderbob]

Kevin,
I'm shocked no one commented on this stuff. This stuff sounds like a great solution to internal corrosion. Looking forward to using Corrosion X on the customers boat this fall.

welderbob

[goatram]

I have a couple of cans of Corrosion X on had that I have sprayed on my Engines and Electrical contacts and wires.

What We have used on Commercial Aircraft Internal Structure is Dinatrol on Northwest Airlines, UPS, Hawaiin, as well as Alaska Airlines. Fed Ex uses LPS -3. Both are a LITTLE GIRL to clean due to the Wax. Still had corrosion in the Bilges on Alaska Aircraft. Lots of it. We started to strip it out to redue it. a week of MEK and and plastic tooth brushes to clean both fwd and Aft Cargo Bays gang of ten guys cleaning in Respirators. The corrosion might have started before the Dinatrol was the Norm. Bilges had Alodine, Zinc Chromite Primer and White Epoxy paint applied.

[AlloyToy]

I've used in on the internals of my fishing reels for years

Curios to why they are applying the stuff internal of the airplanes and the inside of the hull on the boat??? Doesn't the problems begin on the outside of the hull? If so what good would coating the inside do? Not trying to be an A-hole just wondering the thoughts on this???

I had the pressure treated front bunk problem about 3/32 deep........why aluminum boat builders don't put a HUGE warning placard someplace in the boat is beyond me

[kmorin]

AlloyToy, corrosion can begin inside the bilge or below decks area if
#1 water is left in the bilge (ambient humidity, in some locations, can collect as bilge water);
#2 that water becomes acidic (several means to do that including being left sealed for a long time once introduced to the bilge area)
#3 acidic water is left to stand while a boat is stored out of the water on a trailer.

Cure #1 is to put baking soda or ammonia in the bilge to neutralize the acid- short term solution - still needs rinsed and drained.
Full cure (#2) is to rinse the entire bilge area with acid first to clean, then a long rinse and drain finally drying out and installing seals and a vent tube arrangement.

Maintenance wise, all welded aluminum hull should have a drain fitting as close to the bottom of the bottom plate as possible and if the boat is hauled seasonally this should be opened to allow the void to dry out, and to eliminate any water accumulation. If there is water when she's drained its best to test is with Litmus paper ( ph strips ) and make sure it was not acidic or 'too acidic' other wise there is potential for corrosion inside the below decks (bilge) of the boat and a flush with a neutralizing base solution of water should be used.

NOWWWWW... having said all that, this product makes claims that using it's various different components could reduce or eliminate the potential problems of acidic bilge water so these may be as good or better product and method to solve the internal corrosion that can come from oxygen starved water in the bilge. Acidic bilge water can also happen from a mixture of organic material that composted into acid in the bilge OR, galvanic corrosion can begin where carbon or metallic ions are dissolved or suspended in the bilge water.

If the boat is designed to have a sealed bilge, then a dry bilge is the best of all worlds. But if the deck fittings are sealed and there is no vent fitting like a tube inside the hull that runs up and hooks at the sheer line to allow the day's heat cycle expanded or contracted bilge temp air to "come and go"- the deck will vacuum water and organics in the deck hatch seals down into the bilge. This has already been shown to start the interior corrosion cycle.

I worked on a boat that had pitting in the bilge water areas, and it was found to have exposed copper hydraulic lines which were run low in the hull to get to a foredeck area. The bilge (not a sealed deck boat) was salt water and when the waves were big enough her motion sloshed the bilge enough to wet the lines. That got some copper ions into the bilge and in a period of 2 yrs. she pitted from this last gallon or two of water being below the pump suction location... When the copper was pulled and replaced with hose, and the pitting cleaned and welded (major pain the stern) the bilge remained less corrosive and the boat is in use today.

So, corrosion can come from inside the boat if conditions are right to allow bilge water to remain and become corrosive.

Hope this helps to see that there are a couple of mechanisms, all easily avoided, that can cause corrosion?

Cheers,
Kevin Morin
Kenai, AK

[MacGyver]

More questions than answers.

Will corrosion-x attach it self to aluminum if wet?

What if you can't get the corrosion-x into all the areas like the inside top of the hull stiffener? If not you will have a false sense of protection.

I have read corrosion-x does not dry and remains sticky and need to be redone over time, would this be a problems?

If it not possible to keep the inside of the hull dry I would think putting a zinc or aluminum anode inside the hull in the water would be a better solution? It's done in water cooling systems all the time.

[AlloyToy]

More questions than answers.

Will corrosion-x attach it self to aluminum if wet?

What if you can't get the corrosion-x into all the areas like the inside top of the hull stiffener? If not you will have a false sense of protection.

I have read corrosion-x does not dry and remains sticky and need to be redone over time, would this be a problems?

If it not possible to keep the inside of the hull dry I would think putting a zinc or aluminum anode inside the hull in the water would be a better solution? It's done in water cooling systems all the time.

Camper aluminum hot water tanks as well.....a simple anode attached to the hull drain plug seems to be an extremely simple solution

[kmorin]

MacGyver, AlloyToy,

I don't know about Cor-X application uses or durability from using it.. So I'd remark about a few other points.

First zincs inside the bilge won't anything to protect the hull because the corrosion is not known to be stray current (battery induced galvanic corrosion) which pretty much what the sacrificial zinc does for a bare hull or engine in salt water. Engines create a small charge and the alternator a larger one, and the engine's leg is in the water so.... the zincs go/decay/sacrifice molecules first as the point where 'metal is given up' to carry the current to the water.

(Bare) hulls with electrical systems can easily have some stray charge and the hull zincs to the same job- give up the less noble metal to keep the aluminum in tact. So we could say that galvanic corrosion (different metals) and stray current corrosion may ACT the same by removing molecules of the metal as the current flows to the water.... BUT we can't say the all bilge corrosion is galvanic and it can hardly ever be stray current in the bilge since there's a much bigger (infinite) zero potential (earth/ground/sink) just outside that (conductive) metal hull! so why would the current ever stray to the bilge as 'earth'?

cooling or storage system tanks are not in water (hull) they're only lined with liquid so they may 'inside out hulls' but they're not marine hulls unless they're wetted outside AND inside--- like the boat. So a zinc in those one-sided aluminum structures is like hull zincs not like bilge water. If you knew there were different metals in the bilge (cooper pipes, brass fittings, even constantly immersed SS fasteners, then a galvanic cell could have developed but... instead of putting zinc in that bilge- isolating or eliminating the galvanically different metal seems better practice?

Chemical or acid corrosion in the bilge, also carbon rubber products can make the bilge into a 'hot solution' (belts that wear and leave shavings and dust in the bilge water could do this with inboards), is the main cause of the bilge corrosion and zincs won't neutralize acidic ph of that water.

Will Cor-x stick? well the prime location for the corrosion being discussed in at the low point, where (A) potentially acidic bilge water or (B) metal particles might be int he bilge water.... so the low point corrosion reduction/protection/elimination is most important. We have seen some rebuilds here, where the boat is opened up and there's more corrosion or more widespread corrosion than just the bottom along the keel but most of the really deep pitting is along the keel or the very bottom of the boat's lowest points.

So pouring the stuff in, and putting a heater under the bottom (even on the trailer with a tarp ) should mean that there's a way to get this material to the most critically impacted location AND it could be dumped in, wait a bit, and pull the bottom drain and what's left recovered? Then vent the entire area as best possible and "build a fire under the boat" to dry the Cor-x onto the flooded areas?

I have no idea is this is valid in regard Cor-X but the other remarks are valid to my knowledge.

welderbob, remember that the majority of builders don't even etch their boats (even early Pacific Skiffs look like they had mill scale not the new ones) so if those builders won't even go to the simple step of removing a known and easily seen future corrosion cause (!! ) from their metal... I'm not very confident that Corrosion-X would be welcomed by that group of builders- even if it works miracles in corrosion resistance.

Cheers,
Kevin Morin
Kenai, AK