SILVER SPOONS AND HULL POTENTIAL
Can I measure Hull Potential with a
Silver Spoon?
Monitoring the condition of your Boat Hull is a very
straightforward process yielding a quick result which can indicate if there is
a corrosion problem necessitating the replacement of Sacrificial Anodes,
checking of DC leakage sources or just giving peace of mind knowing that
preventative measures are working.
Silver/Silver Chloride Reference Electrode
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.
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!!
