Galvanic corrosion

[gcboat]

Or better known as electrolysis. Had a set of Lenco electric tabs installed two years ago on my Pursuit. Have had the boat out of the water several times since then to do basic cleaning, etc. The other day I was pressure washing the bottom and literally blew off the top of a bolt head securing the tabs to the actuator.
The boat is moored in salt water at a ( what I thought ) safe dock.
So today, after really getting into the whole mess I discovered several of the screws attaching the tabs to the boat hull were pretty eaten up. Four of them were completely gone, just the screw heads showing.
Is the dock "hot", do I have a really bad grounding problem? And now after sanding the bottom of the tabs I can also see some pitting going on there as well. Where do I start looking to fix this problem?

 

[HONKER1]

Re: Galvanic corrosion

Saw this while looking for an anode in the West Marine catalog.
http://www.westmarine.com/webapp/wc...=true&storeNum=5000&subdeptNum=4&classNum=593.
Of course you still have to replace the screws and have a talk with the dock owners.

 

[dingbat]

Re: Galvanic corrosion

I would first check to make sure that the bolts where 316 SS then start looking around for other damage. If it was a "bad dock" you're zincs would have been the first to go followed by any aluminum in the boat.

IF you find no other damage then either the hardware wasn't 316 or most likely you have a serous grounding issue in the tabs. Either an improper ground or one or both of the armatures are leaking current to ground somewhere.

Problems like this are the reason why you'll never find a set of Lenco tabs on any boat I own. Don't belive a word they say. Electric motors and water don't mix.

 

[gcboat]

Re: Galvanic corrosion

Thanks all -

Dingbat, I'm heading off to talk with the installer this morning. Got an electrician heading to the boat dock first of next week. Really would like to solve this little mystery.
Talked with customer service at Lenco this a.m. and she basically said they were internally grounded so nothing else ( such as supplemental anodes ) were really necessary. But I do tend to side with your thoughts on the electrical issue - . Guess I'll just have to deal with these for a bit.

Thanks again,

jerry