What is Cathodic Protection?
Why Does Your Boat or Yacht Need It?
Electrochemical corrosion of metals is one of the most destructive processes that affects a boat during its lifetime. Cathodic protection is designed to prevent corrosion by altering a metal's electrochemical characteristics through the application of electrical current.
Your boat's underwater metal fittings such as propellers, shafts, struts, thru-hulls, as well as the hulls of steel and aluminum, are susceptible to electrochemical corrosion. There are several types of corrosive influences:
Galvanic CorrosionOccurs when two or more metals with different galvanic voltages are electrically connected and wetted by water. It is the result of the more active metal's natural tendency to give up electrical current to the less active metal. Galvanic corrosion may occur in fresh or salt water.
Stray Current CorrosionOccurs when underwater metals are energized by an electrical current that has strayed from an electrical conductor or device powered by a battery, generator or dock power. It is the result of an electrical fault.
Caustic Attack to WoodDamage to the wood occurs from excessive cathodic protection. It is the result of a lack of proper control of cathodic protection or an electrical fault.
Caustic Attack to AluminumDamage to an aluminum hull, stern drive or other aluminum parts occurs from excessive cathodic protection. It is the result of a lack of proper control of cathodic protection or an electrical fault.
The first attempt to control underwater corrosion was developed in the 19th century. This method strategically placed zinc sacrificial anodes on metal fittings. Incredibly, about 98% of the world's pleasure boat owners still use this preventive method! There is no accurate means of controlling the anode's effectiveness using this method. Too little protection results in corrosion. Too much protection can result in caustic attack to wood, a loss of anti-fouling paint or other underwater coatings on metal fittings, caustic corrosion on aluminum boats, and the embrittlement of high strength steel. Using this arbitrary, old-fashioned method, boat owners are never guaranteed 100% protection; they spend more time and money replacing zinc plates; the system's inefficiency causes more zinc and cadmium ions to be released into the water--possible pollutants. The typical zinc wastage for boats ranges from fifty to several hundred percent. There is a better method available.