The outer components of marine and defense vessels are constantly being threatened by the surrounding water. Over time, corrosion can lead to a loss of integrity in the structure, hence the use of marine anodes.
Most metals immersed in water are subject to rust and disintegration caused by electrochemical corrosion. Marine anodes are designed to fight electrochemical corrosion by using the process of galvanic corrosion.
Essentially, galvanic corrosion is caused by placing less-active metals near highly active metals. The process requires the active metal to “sacrifice” itself, attracting the galvanic corrosion to it while protecting the critical components. In this instance, the sacrificial active metal acts as the anode, and the valuable metal the cathode.
Marine Anode Optimization
Anodes aren’t meant to last forever – their purpose is to absorb natural wear, thus protecting surrounding valuable metals from the threat of corrosion.
Marine and defense vessels and structures require the consultation of a marine surveyor during their design. The process of balancing anodes and cathodes in a unit is delicate; too many anodes, and the vessel’s electrical current per anode will be too low, leading to passivation of the anodes due to a decreased rate of dissolution. Anodes consumed too slowly will invariably passivate, losing their function entirely.
Types of Metals
All marine anodes must be suited to the type of water they are meant to be used in. Zinc is suitable for use in saltwater and is not recommended for freshwater use; aluminum is suitable for salt, fresh, and brackish water and has been shown to outlast zinc due to its increased capacity.
Styles and Uses
Plate anodes are used to protect components of marine vessels and structures from corrosion. At Canada Metal, zinc and aluminum anodes are available in teardrop, streamlined, and semi-streamlined format in “bolt-on” and “weld-on” styles. The inserts on either style are made from aluminum or steel.
From marine vessels medium-sized and large, anodes have many water-based applications. These include: bottom plates, sea tanks, bilges, rudders, keels, cargo tanks, ballast tanks, and rudders.