Role of air pollutant for deterioration of Taj Mahal by identifying corrosion products on surface of metals

Abstract

Deterioration of metallic and non-metallic structures and monuments is largely controlled by their surrounding environment. The Taj Mahal, a UNESCO (United Nations Educational, Scientific and Cultural Organization) world heritage situated in Agra of India built in seventeenth century using white marbles, is famous for its aesthetic look. Gradual yellowing and blackening of the monument are matter of great concern, and if not controlled, the heritage structure may lose its glaze and beauty. Extensive studies available on deteriorating effect of the monument miss a vital point related to the pollutants coming from severely polluted River Yamuna which flows very close to the Taj Mahal. To ascertain the possible effects of the pollutants carbon steel, copper and zinc samples were exposed for four years at the premise of Taj Mahal. The surface characterization of the exposed metals with electrochemical impedance spectroscopy, Raman spectroscopy and X-ray diffraction reveals the formation of respective sulphides of the studied metals. The findings suggest that the hydrogen sulphide from the polluted Yamuna River had damaging effect. The wind rose diagram developed at site of exposure further supports the above findings. The corrosion rate of copper was found to be 2.46 mu m/year. This observation as well as identification of corrosion products formed on the metal surface (strong peaks of copper sulphide) provided strong evidences that the hydrogen sulphide evolved from the polluted river accelerated the deterioration of the metal.