internal frame rust protection. feedback on idea

[MickinOz]

Ok the OP is in
How about freshwater and controlling the power down the cable's of downriggers using zinc.
Freshwater guy's have deep water too especially here.

What?

[twisted lines]

By using a voltmeter with a scale from zero to one volt, a series of measurements can be taken which indicate whether or not the boat is being protected from harmful electrical corrosion and if the downrigger cable has the proper positive field to attract fish.

I don't much like to clean or smell like fish, but i learned a lot about it.
.7 to .8 volts is one recommendation for the proper voltage, using cables fishing in deep water to attract fish

[MickinOz]

I'd never heard of this charging the down rigger thing, so I went off and did a little reading.
At least one website I found was a strange mix of psuedo science and sales talk.
It didn't have any explanation as to why they thought zinc could be expected to protect aluminium boats in freshwater.
And they seemed to think fibreglass is such a poor insulator that 0.5 volts would overcome said poor insulation and cause a current to flow.
At least they showed zinc, aluminium and magnesium in the right order for saltwater.
They did warn not to clamp zinc directly to the stainless steel cable.

Apart from what my lecturer told me in chemistry class, my own information mostly came from a book we had at work, the Handbook of Marine Corrosion Prevention. Written by a Lieutenant in the British Royal Navy.
That contained a science based explanation of why you need magnesium in freshwater to protect aluminium, but could get away with much cheaper zinc in saltwater.
It pretty much backed up what my lecturer said.

All a touch irrelevant to protecting a steel trailer frame though.
Zinc will do nicely for that.