I started a new thread per OHB's request. OHB, the annodes look in ok shape. They don't look brand new, but they look to be getting eaten away. They look to be doing their job but I only have 3 anodes on the boat. There is a large one on the rear keel and two at the rear of the boat. There is some pitting towards the rear, but nothing like the front. The closest anode to the front of the boat is the large one on the keel. Where could I place some anodes towards the front of the hull?

If I don't find that the issue is me, since the boat has now been moved from its previous location, what would you do? I know to get the deep pits welded, but would you get it sandblasted and coal tar epoxy it? Should I look to fill in the pitting with epoxy and use coal tar or do I just use the coal tar and not worry about the pitts?

Bamby,

I was wondering the same exact thing about which bottom paint was being used. What is the time frame that this kind of damage would take if it was electrolysis/Galvanic Corrosion?

jtalberts, Are we assured that whoever painted the boat utilized the right and proper paint for aluminum application? I've read other horror stories of folks unknowingly utilizing improper bottom paints resulting in horrendous and devastating results..

The Question below was lifted From Here.

Q - What is wrong with using a copper-based antifouling paint on my aluminum boat?

A - Placing dissimilar metals in proximity to each other on a boat is a very, very bad idea. When aluminum and copper are in the presence of an electrolyte such as salt or freshwater (yes, freshwater is also an electrolyte) a great battery is created, galvanic corrosion takes place and the aluminum hull becomes the sacrificial anode. Damage from galvanic corrosion can be severe to your boat and your wallet. Do not be misled into thinking that applying a thick layer of primer between your aluminum hull and copper-based antifouling paint will provide permanent protection from galvanic corrosion. Paint systems on hulls are easily compromised when striking flotsam and jetsam in the water (or a neighbor with an axe to grind). The US Coast Guard and US Navy take the potential for galvanic corrosion seriously and this is the main reason that ePaints are the only copper-free antifouling paint specified for use on their aluminum fleets. New copper-organic hybrid biocides (i.e. copper-omadine and copper-thiazole) have become popular of late but these materials will also promote galvanic corrosion on aluminum in the presence of an electrolyte.

-------------------------
Respect Our Outdoor Recreational Resources
Leaving Only "Footprints in the Sand"

2003 5.3 Chevy P/U
1972 35' Crest Pontoon Houseboat
2007 90 hp. Yamaha

OHB,

After doing some reading about the Zincs, when the boat was pulled they were completely covered on all sides with a white goo. It was about an inch thick. Could they have been basically neutralized being completely covered?

It was kind of a white crust. It was different than any of the other build up on the boat. It almost looked like corrosion on it. Should I look to add zincs to the front sides of the keel?

Never heard of Goo covered zincs. If you have an "on board" electronic cathodic protection system (Capac or other) DON'T use it without it being checked out. Most Kings Craft didn't have electonic protection systems and didn't have your problem. May or may not have a bearing on the goo. Ike - chime in here. Have you seen this condition?

Remove the zincs before sand blasting. Sand blast the them to provide a virgin surface. Make sure the mounting surface under the zincs is bare and clean before remounting. My Kings Craft had zincs foreward on the each side of the keel as well as the back of the boat.

For sure sandblast and do the Coal Tar Epoxy bit. 2 coats.

The Coal Tar is thick and should take care of all but the worst pits.

After your back in the water get an expert to do a stray current survey of your boat and your slip area.

My opinion is that the problem is recent. The splotchy appearance with depressed centers can't last long before putting holes in the boat. Suggest you inform the marina, where the boat came from, that they might have a peroblem.

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OLD HOUSEBOATER

Edited: 03/12/2012 at 09:38:34 AM by OLD HOUSEBOATER

OHB's advice is right on the money and I would like to add a few points.

Surface prep is VERY important. Do Not scrimp with the blasting. If not prepped correctly the paint will not adhere properly. Make sure to clean all the dust and residue from the blasting off before painting.

Make sure the coal tar you get is a 2 parts product with a part b catalyst. There is a single part out there that is not as good.
Apply 2 liberal coats right after blasting. You don't want to leave the bare hull exposed for weeks before painting.

I would suggest you call the folks at www.boatzincs.com a call concerning anodes. They can give advice as to the type and size of anode's you should use. A friend with a steel boat used them and they were very helpful. Sold him some plastic coated bolt on magnesium anodes along with a test probe and instructions for testing. The idea is that after anode installation and back in water you test your exposure. Then you can cut away plastic exposing more of the anode to get the correct reading from the test probe for your conditions.

I know this is a big job. I did this myself on a 40' Riverqueen I used to own. The boat is still at my marina with 15 yr old coal tar still on the bottom.
It was out last year and still looked very good with only touch ups needed from beaching.

-------------------------
1991 70' Pluckebaum Baymaster
10' AB RIB 25hp Suzuki

Edited: 03/12/2012 at 01:22:00 PM by boatlover

It seems that the Coal Tar is also cheaper than the bottom paint method I have been reading about. It was close to $3600 in just supplies to get it all patched up. OHB I have read before that you prefer Sherwin Williams coal tar? The only issue I have to figure out now is where to block the boat and get it sandblasted. I don't mind getting in the water a little late if if means I am not going to sink in July.

Another question regarding how much coal tar I am going to require. I have taken an estimate that my boat would be 480 sq/ft (40x12). Below is what Sherwin Williams states for the coal tar:

Recommended Spreading Rate per coat:
Minimum Maximum
Wet mils (microns) 11.0 (275) 22.0 (550)
Dry mils (microns) 8.0* (200) 16.0* (400)
~Coverage sq ft/gal (m2/L) 74 (1.8) 148 (3.6)
Theoretical coverage sq ft/gal
(m2/L) @ 1 mil / 25 microns dft 1184 (29)
*See Performance Tips section </pre>

So is it saying that at 1 mil I will get 1184 sq/ft of coverage? Taking loss into account, I should be able to get 2 mil out of a gallon. So I would need 8 gallons to get to the max of 16 Dry mil?

Sorry if I ask so many questions. I am trying to get up to speed with all this and if anything this will be a great learning experience.

Edited: 03/12/2012 at 05:58:27 PM by jtalberts

It's been awhile but I think my 47 took (2) 5 gallon packages and my 55 Pluckabaum took 3 or 4.

I really have no preference on brands of Coal Tar Epoxy. Sherwin Williams was the brand I ended up with.

2 points that need repeating:

1. Apply as soon after blasting as possible. Raw Aluminum starts to form protective oxides when combined with moisture in the atmosphere. These oxides can reduce adhesion applied coatings. In other words apply the Coal Tar the next day.

Be sure to have enough help. You aren't going to mix this stuff with a stick. A 1/2 inch drill motor and a big mixer tool is a must. The 1/4 drill that you mix your gallon of ceiling paint won't cut it. If your going to roll it on you need 2 guys rolling and 1 guy chasing material and doing touch ups.

2. IMPORTANT !!!!!!! apply the 2nd coat within 24 hours. Adhesion is the reason.

Spraying is the way to go but most yards don't like too because of overspray concerns.

Are you having this done or doing it yourself?

Normally this stuff comes in 5 gallon packages (4 gallons of stuff and 1 gallon of hardner) GET AN EXTRA PACKAGE THAT YOU CAN RETURN IF YOU DON'T NEED IT.

Putting this stuff on too thick is not a sin and God won't punish you for it.

Normally anti fouling paint is NOT applied over CTE. In any event it won't stick untill you have at least a year of ageing on the bottom.

On an Aluminum boat you should be set for 5 to 10 years or more if you do touchups every 2 or 3 years.

Coal Tar Epoxy was designed to protect underwater concrete and steel structures. It is used world wide on dams bridges and other structures needing maximum protection. Hard stuff to beat.

-------------------------
OLD HOUSEBOATER

You've been a tremendous help. I am hoping to have at least 4 people workin on the boat and having the wife be our gopher. Hopefully I can get the marina to put my boat in a good enough spot for blocking and blasting.

It would be a GREAT service to the community if you would do a PHOTO record of the project. Not many people have even heard of Coal Tar Epoxy. Many that have think it's something out of history.

There are some things out of the past that are just as good or even better than current high dollar materials. The Coal Tar System is one of them.

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OLD HOUSEBOATER

I will certainly do that.

So I was poking around the boat this weekend and I was looking at the Galvanic Isolator. It appears that one side is connected to the shore power ground and the other is connected to the hull. From reading, about the isolators, the isolator should be connected to the same ground as the batteries? I will get some pictures tonight as I will be heading to the boat.

UPDATE:

Here are the pictures



Here is where it connects to the hull



Here is the whole thing:





Edited: 03/19/2012 at 06:12:49 PM by jtalberts

That is not right. The shore power ground should go through the galvanic isolator not spurred off to the side - the picture on the side shows that. I am sure others can explain it better. Look at www.yandina.com for schematics.

I believe it should be from shore ground to house ground. I would say this galvanic isolator is doing nothing good. Additionally, it is my understanding this galvanic isolator is for shore power only and should be connected to your house ground (110v).

It is definitely not wired where it can do its job. It is wired to where it can be a potential bridge between AC ground and DC ground. The best case scenario is that nothing happens. The worst case is that you have a short to ground on the AC side and your hull gets electrified.

Does this look like a smoking gun for the pitting issues that I have?

This is lifted from Ike's site which is an extremely informative site on practically anything "Boating" anyway...

ELCI: Electrical Leakage Circuit Interrupter

Combined with the main circuit breaker should be an ELCI (Electrical Leakage Circuit Interrupter). An ELCI detects current leaking into the water. It does this by measuring the current in the black (hot) wire and the return current in the white wire (neutral). If everything is ok the difference between the two should be zero. If there is an imbalance, that is less coming back than is going, and this imbalance is 30 ma or more for 100 milliseconds then the ELCI trips and shuts off all power. This is to protect people in the water, or touching metal that is in contact with the water. See Page ten for more on ELCIs.

From the main breaker the wiring should go to a distribution panel, with circuit breakers for each separate branch circuit. The main breaker can be combined with this distribution panel. This panel should be rated for marine use. In 1995 a houseboat manufacturer who used a distribution panel designed for household use, had to recall several thousand houseboats and replace the panels. Several people died from being shocked, some while swimming near a houseboat. So as well as resulting in deaths, this cost the manufacturer so much he ended up having to sell the company. So do it right the first time.

The wire should be triplex, marine rated UL 1426 boat cable. This cable contains three wires, the black, white and green. See the cable here. This looks very much like standard romex cable used in homes but is much better suited for the marine environment. In addition to meeting all the chemical and oil resistance requirements, it is stranded tinned copper, which is very corrosion resistant. It is rated for 600V. Additionally, the outer plastic sheathing is abrasion resistant. This is the only wire the Coast Guard allows to be used without grommets or other abrasion protection where it passes through holes in bulkheads or other structure. However, you should still provide this protection for safety.

But before you wire up the boat you should be aware of several problems that can occur. If the green wire is connected to the ground on the engine block, as it should be, along with the DC ground, then it is possible for stray DC currents to exist on the metal fittings in the boat. These DC currents are not enough to cause a shock or fire hazard, or trip any breakers, but they will result in galvanic corrosion. If you recall my discussion of how a battery works, you will remember that a battery is two dissimilar metals in an electrolyte. If you use the grounding bus and connected all the metal together and then accidentally introduce a DC electrical current, then you start the current flowing between the dissimilar metals. One of them is going to be eaten away. The number one victim is aluminum lower casings of stern drives and outboards. So, by protecting yourself and everyone on your boat from shock you have aggravated the problem of galvanic corrosion. See Corrosion On Boats. Do not under any circumstances cut the green wire, there is a solution! It is called isolation and can be done several ways.

ISOLATION

Galvanic Isolators:

One way of isolating the AC on the boat is a galvanic isolator. In the ABYC standards the green wire is not allowed to be broken by any device, except a galvanic isolator. The galvanic isolator prevents stray DC currents from passing through the green wire, while at the same time it will pass AC if a ground fault occurs. So, you still have ground fault protection and have now added protection against galvanic corrosion. A galvanic isolator is a small electronic device made up of diodes. It is inexpensive, but the isolator can fail and even with a monitor for the isolator you won't know it has failed. But this is better than no isolation.

A-28 Galvanic Isolators 07/08 http://www.nmma.org/assets/cab...Isolators_Standard.pdf (an old version of the ABYC Standard.

Note the Bold emphasis above "is mine" on topic...

-------------------------
Respect Our Outdoor Recreational Resources
Leaving Only "Footprints in the Sand"

2003 5.3 Chevy P/U
1972 35' Crest Pontoon Houseboat
2007 90 hp. Yamaha

Hopefully Endurance will chime in - he seems to have more knowledge about this sort of stuff. I do not know if it is a "smoking gun" or not. If you are carrying voltage on your AC ground and if the galvanic isolator is passing that voltage through, then you are electrifying your hull and that electricity has to go somewhere. And, in the process of going somewhere, it could take pieces of your hull with it.

If it was in the water, I would tell you to disconnect it from the hull and put a good voltmeter between the wire and the hull and see if you are carrying any voltage.

I would say it is highly probable that this is your culprit.

No matter what, it needs to be tested and installed correctly.

Just for reference I found this article as well that pretty much confirms this thing is setup wrong.

http://www.sailmail.com/grounds.htm

AC Ground
See Practical Sailor August 15, 1995 for a detailed treatment of the green wire. The best solution is a heavy and expensive isolation transformer. The acceptable solution (for the rest of us) is to install a light and inexpensive Galvanic Isolator in the green wire, between the shorepower cord socket on your boat, and the connection to the boat's AC panel. Then, connect the grounding conductor (green) of the AC panel directly to the engine negative terminal or its bus. Note that this meets ABYC's recommendations. In choosing Galvanic Isolators, make sure that you select one that has a continuous current rating that is at least 135% the current rating on the circuit breaker on your dock box. Certain Galvanic Isolators (e.g. Quicksilver) include large capacitors in parallel with the isolation diodes, which in certain situations theoretically provide better galvanic protection. Unfortunately, these units cost substantially more than conventional Galvanic Isolators. If you feel like spending real money on galvanic isolation, you might as well do it right and buy an isolation transformer.