Question

Why presence of CO2 in water increases rusting?

Answer 1

If excess of CO2 is present in water then the oxygen present in CO2 oxidises the element present in water. Thus an oxide layer is formed resulting in rusting. This method is called oxidisation. For example iron oxidises from Ferrous to Ferric i.e, Fe^+2 to Fe^+3 when it is kept in water containing excess of CO2