How do ocean (or underwater) support beams for a bridge resist corrosion/erosion/rust from water?

Question

I never understood how underwater bridges never collapse. Like they are constantly submerged under water, how do they resist rust? Like ships and other man made objects in the water always het destroyed so how do they do it with bridges?

In: Engineering

Answer 1

Water causes chemical corrosion, particularly salt water. Engineers know this, and choose materials that are corrosion resistant, or coat materials in protective paint/concrete/… so they are not exposed to as much water.