Zinc

Galvanising works because zinc is more readily oxidised than iron, so a zinc coating protects steel even where it is scratched through — the exposed iron becomes the cathode and the surrounding zinc corrodes instead. Roughly half of all zinc produced goes to that single job. India was smelting zinc at Zawar in Rajasthan by the twelfth century, centuries before Europe managed it, and Alessandro Volta's 1800 pile — the first battery — was a stack of zinc and copper discs separated by brine-soaked cloth. Biologically zinc is second only to iron among trace metals: about 300 enzymes require it, and the zinc finger, a small protein fold organised around a zinc ion, is one of the most common DNA-binding motifs in the genome. Dietary deficiency is a major cause of stunted growth in children worldwide.