Testing for Stray DC in a Marina to save your Anodes.

A metal hull in water will inevitably have the potential to become corroded. Add a little stray direct current (DC) and this can become devastating.

Careful owners will take the necessary precaution of employing some cathodic protection by attaching Sacrificial Anodes, usually Aluminium, Magnesium or Zinc. Others will simply protect the hulls with underwater coatings of some description. Larger vessels tend to apply Impressed Current systems (ICCP) where a DC current is applied in a controlled fashion to protect the structure.

The Anodes employed to protect the metal Hull of a boat are the first items to be attacked and lost to stray DC. The source is normally external but can be caused by badly installed or unearthed electrical appliances on the boat.

Using a Boat Meter Kit will enable the owner to test for the presence of any stray direct current (DC) but will also help identify the location of the source. If this happens to be a pontoon with a faulty earth connection or an errant vessel it is then possible to relocate your boat to avoid further issues.

The test is a simple one. Simply connect the REDOX electrode to the RED terminal and the 9999 Cathodic Protection Reference to the black terminal of the Boat Meter. Lower the Electrodes into the water and note the Water REDOX reading. Normally this is around +80-250 mV.   In the presence of stray DC the result can be negative or positive depending on the proximity of the REDOX electrode to the source of the Stray DC.  The closer to the source the higher the reading.  Move the electrodes around the Boat or along the pontoon to see where the largest result is.

To check if there is any stray DC perform the BUCKET TEST.  This is where you measure the water in the Marina then remove a Bucketful and test the isolated water.  If the result is different you have stray DC!!

Take a look at the Boat Meter Kit