Iron oxidation, known as rust formation, causes enormous loss in term of property damages and associated economic risks. Depending on the degree of formation, rust consists of several layers of iron in different oxidation states. The brownish top layer is mostly iron (III) oxide-hydroxide [FeO(OH), Fe(OH)3] while the deepest black layers possess iron oxide (Fe2O3.nH2O). The flaky nature of surface rust meditates diffusion of oxygen and water to inner material sections which can lead to total disintegration of iron mass. As a result, it is desirable to remove rust and protect fresh surface from oxidizers. The common rust removal reagents are mainly based on complex formation of ferric ion with organic and inorganic acids such as citric acid, oxalic acid, and phosphoric acid. Rust removal ability is typically a qualitative observation which makes direct comparison between treatment options cumbersome if not impractical. In our recent work (Ahmadi et al., 2015), we have developed a colorimetric assay to measure ferric concentration in rust removal treatment media using a bacterially-produced siderophore (yersiniabactin) in comparison to a commercial rust removal reagent. In this approach, ferric concentration is correlated to the mass of rust being dissolved in the presence of different removal agents. This assay is based on a modification of the 1, 10-phenanthroline assay (Skoog and West, 1979) to enable detection using a 96-well plate format for higher throughput screening and assessment.
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