Lead is a bright and silvery metal with a very slight shade of blue in a dry atmosphere. Upon contact with air, it begins to tarnish by forming a complex mixture of compounds depending on the conditions. The color of the compounds can vary. The tarnish layer can contain significant amounts of carbonates and hydroxycarbonates. The dull gray color of lead pipes and cables is caused by the oxygen of the air combining with the metal so as to form a very thin film or skin composed of an oxide of lead. Lead is not at all easily corroded, or eaten away. Unlike iron and steel, it does not need protection by painting.