ANODES... SACRIFICIAL


By David Pestridge MIMMS


David is a yacht and small craft surveyor based in the UK south west region. He founded White Hat Marine Surveying in 2008 when he retired from the British Army after a 17 year career with the Royal Electrical and Mechanical Engineers.


Building on 20 years’ experience as a sailor and boat owner he completed the highly respected IIMS Diploma in Yacht and Small Craft Surveying.


David is a Chartered Engineer, has a Master’s Degree in science and is a member of the IIMS management board.


Sacrificial anodes are something every boat owner should be aware of, yet not every boat owner will need them. The principle is quite simple; the material that the boat is made of and the environment in which it is kept has the propensity to cause serious metal loss through corrosion if things get out of balance. Sacrificial anodes are there to help mitigate minor imbalances in this situation but cannot in


themselves fix a problem that is out of control. That all sounds rather nebulous doesn’t it?


The process we are concerned with here is galvanic corrosion; the corrosion of one metal in the presence of another where both are electrically connected by a conducting medium. The variables here are the types of metal involved and the medium in which they


92 | The Report • September 2020 • Issue 93


are used (fresh, brackish or salt water). We can deduce which metals are more susceptible to galvanic corrosion by considering their relative potential in a series known as the Galvanic Series. Here is a simplified galvanic series for a selection of typical marine metals in salt water (the relative order of the metals may change slightly in different marine environments).


...a waste of money?


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