The answer is rusting of metal such as iron. Iron is the most common metal in the world and has been mined and used in numerous construction of economic importance such as buildings , boats, water pipes, and etcetera. However, the redox reaction between iron and oxygen weakens the metal through rusting (which makes the metal brittle).
4 Fe2+ + O2 → 4 Fe3+ + 2 O2−
One way to lessen the effects of rusting is through galvanization (which is the application of a thin protective layer of metal such as zinc on the iron) or by painting the iron metal.