Spectroscopic identification of protective and non-protective corrosion coatings on steel structures in marine environments

Corrosion research, and the need to fully understand the effects that environmental conditions have on the performance of structural steels, is one area in which Mossbauer spectroscopy has become a required analytical technique. This is in part due to the need to identify and quantify the nanophase iron oxides that form on and protect certain structural steels, and that are nearly transparent to most other spectroscopic techniques. In conjunction with X-ray diffraction and micro-Raman analyses, the iron oxides that form the rusts on steels corroded in different marine and other environments can be completely identified and mapped within the rust coating. The spectroscopic analyses can be used to determine the nature of the environment in which structural steels have been, and these act as a monitor of the corrosion itself. Mossbauer spectroscopy is playing an important role in a new corrosion program in the United States and Japan in which steel bridges, old and new, are being evaluated for corrosion problems that may reduce their serviceable lifetimes. Mossbauer spectroscopy has been used to characterize the corrosion products that form the protective patina on weathering steel, as well those that form in adverse environments in which the oxide coating is not adherent or protective to the steel. Mossbauer spectroscopy has also become an important analytical technique for investigating the corrosion products that have formed on archeological artifacts, and it is providing guidance to aid in the removal of the oxides necessary for their conservation. (c) 2005 Elsevier Ltd. All rights reserved.