Corrosion resistance of the Dhar iron pillar |
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| Authors: | R Balasubramaniam AV Ramesh Kumar |
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| Affiliation: | a Department of Materials and Metallurgical Engineering, Indian Institute of Technology, Kanpur 208 016, India
b Electrochemistry and Corrosion Division, Defense Materials and Stores Research and Development Establishment, Kanpur 208 013, India |
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| Abstract: | The corrosion resistance of the 950-year old Dhar iron pillar has been addressed. The microstructure of a Dhar pillar iron sample exhibited characteristics typical of ancient Indian iron. Intergranular cracking indicated P segregation to the grain boundaries. The potentiodynamic polarization behaviour of the Dhar pillar iron and mild steel, evaluated in solutions of pH 1 and 7.6, indicate that the pillar iron is inferior to mild steel under complete immersion conditions. However, the excellent atmospheric corrosion resistance of the phosphoric Dhar pillar iron is due to the formation of a protective passive film on the surface. Rust analysis revealed the presence of crystalline magnetite (Fe3−xO4), α-Fe2O3 (hematite), goethite (α-FeOOH), lepidocrocite (γ-FeOOH), akaganeite (β-FeOOH) and phosphates, and amorphous δ-FeOOH phases. The rust cross-section revealed a layered structure at some locations. |
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| Keywords: | A Iron B Polarization B IR and Mö ssbauer spectroscopy B SEM C Rust |
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