Products of corrosion were obtained from low alloy steels submitted to total immersion tests in solutions containing sodium chloride at different concentrations, during seven days. In order to properly characterize the adherent (AR) and the non-adherent rusts (NAR), a methodology including room temperature Mössbauer spectrometry, diffuse reflectance infrared Fourier transform spectroscopy, Raman spectroscopy, scanning electron microscopy and X-ray diffraction was addressed. The techniques showed that the AR samples were composed of non-stoichiometric magnetite, goethite, akaganeite and lepidocrocite. The composition of the NAR samples was the same, but with very small amounts of magnetite. Different cell parameters and mean crystallite sizes were found for all phases presented in AR and the NAR samples. The corrosion rates were higher than 580 μm/y. The ratio of the abundances of goethite to the sum of lepidocrocite, akaganeite and magnetite were less than one.
Bibliographical noteFunding Information:
Authors greatly acknowledge to CODI-Universidad de Antioquia (Projects E01248CE and Sustainability Programs during 2007–2008 for both the Solid State and the Scientific Instrumentation and Microelectronic Groups) and CIDI-Universidad Pontificia Bolivariana (Project 889-05/06-27) for financial support. Thanks go to M. Pérez of Universidad Nacional of Colombia Sede-Medellín for the SEM measurements.
- Corrosion and protection
- Mössbauer spectrometry
- Raman and infrared spectroscopy
- X-ray diffraction