Many boat owners will have read that to measure the Hull potential they require a Silver/Silver Chloride (Ag/AgCl) reference electrode. This is correct, the key thing here is not that it contains Silver but that is a reference electrode. 

The Hull potential is the Potential Difference in mV between your boat Hull and a stable reference electrode. To do this the reference part of the cell must not change regardless of the environment it is put in. If the Boat and the Reference change you cannot know the Boats Hull potential with any degree of accuracy.   The Ag/AgCl reference electrode provides a conducting medium to allow the completion of the circuit but its potential does not change. Therefore any mV potential is solely representative of the Hull.

The Silver Spoon

The Silver spoon is very useful if you want to stir your tea or control the amount of Sugar you take but it is not a reference electrode. If used as the other half of the circuit to your Boat Hull you will get a reading. It will however not be accurate or consistent.  You get a result because a Silver Spoon will conduct.  Unfortunately Silver itself oxidises pretty quickly. You will notice how quickly it loses its shine as a Silver Oxide layer becomes visible. This is oxidation and is a similar process to the one going on with the Boat Hull.  During this process the mV reading changes and you may attribute the change to the Hull when it could as easily be the Spoon that is changing!!

Solution.

To measure a Hull potential you must use a Reference electrode. 

Required Equipment

ps: If you must use a spoon use a solid Platinum or Gold one. The result will still not be as good as a Reference electrode but it beats a Silver one!!

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