(a) The Statue of Liberty is covered with a copper skin, and was originally brown, as shown in this painting. The formation of the protective layer is a form of passivation, which is discussed further in a later chapter.įigure 1. Fortunately, formation of the patina created a protective layer on the surface, preventing further corrosion of the copper skin. These three compounds are responsible for the characteristic blue-green patina seen today. ![]() As a result, sulfur trioxide, carbon dioxide, and water all reacted with the CuOĢCuO( s) CO 2( g) H 2O( l) ⟶ Cu 2CO 3(OH) 2( s) (green)ģCuO( s) 2CO 2( g) H 2O( l) ⟶ Cu 2(CO 3) 2(OH) 2( s) (blue)ĤCuO( s) SO 3( g) 3H 2O( l) ⟶ Cu 4SO 4(OH) 6( s) (green) Copper metal is oxidized to copper(I) oxide (Cu 2O), which is red, and then to copper(II) oxide, which is black.ĢCu( s) \fracO 2( g) ⟶ 2CuO( s) (black)Ĭoal, which was often high in sulfur, was burned extensively in the early part of the last century. The oxidation-reduction reactions of copper metal in the environment occur in several steps. The copper that is the primary component of the statue slowly underwent oxidation from the air. It was brown, the color of its copper “skin.” So how did the Statue of Liberty change colors? The change in appearance was a direct result of corrosion. When this statue was first delivered from France, its appearance was not green. The Statue of Liberty is easily identified by its height, stance, and unique blue-green color (Figure 1). The Statue of Liberty is a landmark every American recognizes.
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