Which of the following metals would act as a sacrificial anode (cathodic protection) for iron? Check all that apply.
Sn
Mg
Zn
Na
Cu
We need to choose those elements who preferrebly oxidise(i.e. more eager to loose electron than iron and so its oxidation potential must be higher than iron. Now check the electrochemical series and pick the elements from table below Fe and compare with your available four options). These are: Na, Mg and Zn. In principle Na qualifies but due to its high reactivity with water(Na+H2O=H2+OH-) is a proble. So Na is not used and Zn,Mg are available options with us.
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