A little further reading indicates that a true sacrificial anode system can never
cause overprotection - you need an impressed voltage for that to happen, i.e., you have to apply
a potential. So if the Electroguard 208 is truly sacrificial, what the heck does an overprotection region on the meter mean? Another claim is that in fresh water, zinc will form a zinc hydroxide layer effectively isolating the zinc from the water and rendering the system useless. Apparently that's why aluminum is the anode of choice (and can be used in both fresh and salt
waters). Perhaps my first experiment
should be to don mask and flippers and wire brush the zincs to see what happens? And is the Electroguard 208 sacrificial or impressed voltage? I was under the impression it is sacrificial. The other issue is the use of a silver/silver chloride reference elctrode in fresh water - appropriate for salt water
but not for fresh (I seem to remember the correct electrode is based on sulfate, but not for sure). So if the reference elctrode is wrong the voltage reading will be wrong. Is this part of the problem. This is something I really want to understand, and electrochemistry was never my best subject.