About Corrosion

What is Cathodic Protection and 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:

The 902 Test Instrument is used to dermine Effectiveness of Cathodic Protection on your boat or yacht. Check Bonding System Integrity, AC Shoreline Interference and Trouble Shoot AC and DC Electrical Systems.


  • Galvanic Corrosion -- occurs 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 Corrosion -- occurs 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 Wood -- damage 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 Aluminum -- damage 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.

Electro-Guard, The First Choice in Cathodic Protection


For over thirty years, the Electro-Guard product line has provided a reliable and cost-efficient method of cathodic corrosion prevention. A constant protection level is maintained by an electronically controlled system. Accurate, easy-to-use monitors measure cathodic protection performance and indicate influences by a stray electrical current should an electrical fault occur.


Electro-Guard's models are specific to boat size and hull construction--including fiberglass, wood, aluminum and steel boats to more than 300 feet long. Installation at the time of construction or purchase, or as an add-on is as easy as a phone call.


Electro-Guard is committed to providing the best cathodic protection systems to the recreational boating and yachting industries. From research and development to product design to responsive customer service, Electro-Guard, Inc. is the reliable source for cathodic protection. We grew up in the recreational boating industry--we are proud of our responsiveness to the boat owner's needs. Our extensive experience and technical knowledge ensures that each Electro-Guard product protects boats from all types of electrochemical corrosion.


Electro-Guard's unique Cathodic Protection Systems are the yacht owner's answer to successfully preventing expensive damage to underwater metals. Our innovative product line is easier to use, more cost-efficient, and less polluting than traditional systems. Electro-Guard's systems work full-time protecting your boat.


A modern corrosion prevention system saves time, money, and provides a constant level of protection throughout the life of your boat. Investment in an Electro-Guard Cathodic Protection System is the logical choice.