Use of Sacrificial Anodes on CB-Series Data Buoys
are recommended for use on CB-Series data buoys any time they will be used in
saltwater environments. This helps to prevent corrosion on the stainless steel frame, as zinc is a more
active metal that will be consumed while protecting the stainless steel.
Anodes sourced from NexSens are sized specifically for installation onto buoy frames and instrument
cages using a pair of screws provided with the anode. They will typically need to be replaced
approximately every 6 months, though this may vary depending on factors such as the temperature and
salinity of the saltwater environment. Buoys should be regularly inspected and anodes replaced any
time it appears they will be consumed before the next scheduled maintenance. It is often a good idea to
have two anodes installed onto a buoy – one on the frame and one on the cage – and replace them
intermittently to ensure that there is always sufficient protection for the stainless steel. Anode
replacement will require a 4-mm Allen wrench to remove the pair of screws connecting the two anode
halves.
Zinc is chosen for the anode material because it is a readily-available metal with a
(-0.76V) than the steel of the buoy frame. This offers the steel what is known as
, where oxidation reactions are transferred away from the steel to the zinc when placed in
highly ionic environments such as saltwater in the case of a buoy. The zinc is slowly consumed by the
process, hence the term sacrificial anode.
In theory, other materials besides zinc can be used as the anode as long as they rank lower on the
reduction potential scale than the stainless steel. Generally speaking, the larger the difference between
the metals on the scale, the faster the rate of the oxidation-reduction reaction. Materials with lower
reduction potential than zinc may therefore be consumed more rapidly and require more frequent
changes. Regardless of anode material chosen, frequent inspection and replacement of anodes as
needed can extend the life of a data buoy significantly in saltwater.
Sacrificial anodes are normally not necessary for buoys used in freshwater except in special
circumstances. It is therefore generally recommended only to order anodes with buoys intended for use
in brackish or saltwater.
Sacrificial zinc anodes.
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