Why gold never rusts: Scientists uncover its atomic secret

The Statue of Liberty has stood at the entrance to New York Harbor for nearly 140 years, instantly recognizable by its green color. But when the monument was unveiled in 1886, it looked very different. Its surface was the warm metallic color of copper, the material from which it was made. Over nearly three decades, oxidation gradually covered the statue in a thick layer of patina, a term for compounds that form on materials during prolonged oxidation. The exact chemical composition of such layers depends in part on surrounding humidity. New Yorkers eventually became accustomed to Lady Liberty’s green appearance, especially once it became clear that the patina was acting as a natural protective layer, preventing the copper beneath it from corroding further. But there is one metal that would have avoided the color change altogether: gold. Gold is not only more valuable and luxurious than copper.