The galvanization of steel is a chemical process of applying a protective coating of zinc only to the steel.For galvalume steel, it undergoes the same process, except the coating is a combination of aluminum, zinc alloy and silicon.Both steels serve to give a unique look to your home, and increase its curb appeal. The choice between galvalume vs. galvanized really depends on preference, however, as far as longevity, galvalume will very often outlast galvanized.