CAPAC and Hull Potential question

[Tranquilo]

Thanks! Got enough of the other stuff around to make a few

[Fastjeff]

..."For those that keep their boats in fresh water year around... I highly recommend the use external mag. anode."

Right on!

Jeff (happily "Deplorable and Irredeemable")

[barkleydave]

Jeff is right on! I have used the external mag. anode for years... Not only are my readings good... I have little wear on the fixed anodes on keel etc. Last year when we took her back to bare there was NO corrosion on the hull, rudders etc.

safe boating,
dave

[Tranquilo]

I've been adding new anodes to the boat and it isn't making a difference on my CAPAC. Still reading 0.1. Might it be busted? My oil gage just busted so maybe I have an issue in the panel?

Added another 6ft keel anode (I have 2 on there) 2x new shaft anodes, 5 dangling anodes, new trim anodes, new rudder anode coming this weekend (swapping the prop underwater - should be interesting) - I still believe I have a corrosion issue, just can't find the source and the 5 electricians I contacted who could help me, laughed and said "no thanks" when I told them what size and age my boat was. They wouldn't even accept $300 just to come out for an hour..

[barkleydave]

One an electrician who specializes in AC will have no idea what you are talking about. AC is not a significant source for galvanic corrosion.

1. You must have continuity between your anodes and the hull. Also the Silver Silver Choride cathode may have been sanded. If it was or has been painted or both it will destroy the cathode. The coating is VERY thin!

Optimum reading should be between -.95-1.05 neg. millivolts A reading around .80 + is acceptable in fresh water.

For the $300 dollars you were willing to spend.... a suggestion would be to buy the portable Silver Silver Choride cathode from Boatzincs.com. You can then check for your self and can use in the future. You can also verify shaft coupler isolation with the unit. etc.

http://boatzincs.com/corrosion-referenc ... specs.html

safe harbors,

dave

[jralbert]

What Dave said. If you are adding zinc and the Capac reading doesn't change, suspect the Capac (you can also contact them and discuss with a tech person). Jeff built a meter himself and if you offer him donuts here, he might be willing to tell you how he did it. I used it successfully many years ago when we both boated the Chesapeake Bay

[MarinetteBud]

After reading all four pages of information on the protection of our aluminum boat hulls and how to keep corrosion under control.....(I still have a lot to learn).... I got wondering why I never see aluminum hull pontoon boats with badly corroded hulls in my fresh water lake? I have never seen any corrosion monitors on them either. I am not saying they can not have corrosion problems...I just hardly ever see it. I have been cleaning many pontoon hulls for over 25 years. Why are our boats more problematic that aluminum pontoon hulls? This includes outboard and I/O pontoon boats. They all have DC power, no AC power. Very few of my customers know anything about having the proper anodes.

Does a two part epoxy barrier coat protect our hulls from corrosion.....or make little difference?
I also noticed that my 29ft Family Cruiser had tiny whitish spots (corrosion?) on either side of my engine area on the inside / bilge side of the hull...no where else did I see it. Is that an indicator of eletrolisis or just normal pattern of corrosin for aluminum?
Bud

[barkleydave]

A short answer:
Unpainted aluminum hulls (houseboats especially) Have large surface areas when left bare the electrons are spread out over a large area and that reduces galvanic corrosion. In fact aluminum coast guard patrol boats (the smaller 41 footers etc) do not paint the hull bottoms. Instead they pull and clean the bottoms more frequently.

Pontoon boats have few sharp edges chines etc. Again the large surface are dissipates the electrons. Also few if any dissimilar metals from thru hulls etc. Outboards do have anodes on the lower units.

If you ran a bare bottom Big M you would also have less chance of corrosion but the trade off would be a dirty bottom and less efficient hull. Large aluminum houseboats do not plane and more times than not spend 99 percent of their time at a dock.

safe harbors,

dave

[Fastjeff]

Excellently said!

Jeff