I follow battleship New Jersey on YouTube. One of the recent topics is how the hull around the propellers can corrode more than other areas of the hull. Because of this, the navy installed sacrificial anodes.
Why would a large ship corrode around the propellers more. How to anodes prevent this?
In: Chemistry
Water corrodes steel because of atomic forces that make iron and oxygen want to bond together. These forces are magnified in salt water. A sacrificial annode works by pulling those forces from the metal you want to save to the small block of zinc metal. This works because zinc wants to form zinc oxide more than steel wants to form iron oxide.
However the alloy that makes up ship propeller create forces closer to the ones zinc experiences when attached to normal steel. So you need more zinc to create a greater attraction for oxygen to bond with the zinc rather than the propellers.
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