electrolysis

[anchorout]

A question on electrodes. My understanding of electrolysis is that it is caused by current passing through metal in a salt water environment. The current could be caused by contact of dissimilar metals or electrical current from batteries or other onboard devices, or badly designed shore power.

I have hydraulic trim tabs with plastic cylinders. The stainless steel tabs are mounted to the fiberglass transom and to the cylinders with stainless steel screws. Is there any reason would I have to add anodes to the tabs?

 

[Sunbeam]

I'm sure others can explain in detail, but Tabman (fantastic Bennett representative) recommends putting zincs on the trim planes when in salt water (and perhaps in other specific situations such as certain marinas).

I haven't had my boat in salt water yet, but before I installed the trim planes I drilled a hole to accept one half of a lozenge shaped anode on top of the plane (as recommended by Tabman). I carry them along to install when needed. I'll see if I have a photo.

(He didn't recommend the zincs that go on the angle bracket plane-to-actuator fastener, because then if/when the zinc wears down or falls off the trim plane could become loose.)

Edited to add: Here are a couple of photos (not that you exactly asked how to mount an anode, I realize, but figured you might like to take a gander at them since you very well may add them).

This shows the holes I drilled so that I could add "half lozenge" anodes later - you can see it just forward of the bracket where the actuator attaches. Ignore the big snaggly spring! I was in the process of installing the trim tabs when there was a sudden "bang" and parts went flying.... ran to the transom and found the bottom of the actuator had basically exploded :shock: Some of the parts were pretty far away. Bennett promptly sent me a new one (said it must have been defective as there was nothing I could have done to cause it). The position it ended up in just made it a good photo for showing the hole I drilled for future anode installation.



Here is another type of tab (Lenco?) with a sightly different shaped anode than the ones I have, but similar idea:



This is the type of anode I have to put on the tabs. Just one half of it on the top of the plane (as per Tabman's recommendation). I think it's usually called a rudder anode.

 

[bridma]

I have the half lozenge zincs as mentioned by Sunbeam. It is installed as recommended by Tabman. I change them every Dec when I pull the boat out of the water after 8 months in the chuck. The zincs are about 50% done for, but I still put new ones on for the coming season.

Martin.

 

[thataway]

Galvanic action is due to different metals. Electrolytic corrosion due to stray currents and miss wiring. The difference between them is significant as is the prevention. If you are leaving your boat in the water significant periods of times, you need to take precautions for each. If your boat is improperly wired, then it needs to be fixed.

 

[anchorout]

Thanks to all. By your definition of electrolysis and galvanic corrosion, you have answered my question.