The application of sacrificial anodes in ships
First, the role of sacrificial anodes
The sacrificial anode "sacrifices" itself and is consumed to "replace" the propeller, propeller, rudder, engine or other important metal parts, and the sacrificial anode is "eaten" due to galvanic corrosion. Sacrificial anodes are made of relatively inexpensive metal and are specifically designed to prevent corrosion of the ship's more expensive metal components. Sacrificial anodes, known as "reactive" metals, are commonly used in marine corrosion.
Traditionally, sacrificial anodes were made of a zinc alloy, hence the name "zinc block", but they can also be made using magnesium or a special aluminum alloy. Sacrificial anodes are essential for ships to help prevent damage from corrosion to very expensive onboard equipment, generally referring to the underwater metal parts of a ship.
Sacrificial anodes come in all shapes and sizes, but they work on the same principle and must be connected "electrically" to the hull being protected, usually by metal-to-metal, to the precious metal parts of the ship that need to be protected. So, if you get close to the ship, you'll see pieces of metal attached to the rudder, outboard motors, and propeller shafts, among other things. The sacrificial anode constitutes the negative electrode of the battery and is electrically connected to the metal to be protected.
Because the sacrificial anode is more electrically active in metal, it is dissipated, forming the negative electrode (anode) of the battery in the electrolyte. For example, in seawater, the anode is connected to other metals that need to be protected and is completely immersed in water, so the anode will always corrode. The positive electrode of the "battery" must be the metal (cathode) to be protected, such as a propeller, propeller, engine, etc. The saltier or more polluted the water, the more conductive it is and the faster the sacrificial anode will be corroded.