Janis Heuer & Andreas Lüttge
npj Materials Degradation (2018) 2, 40
The corrosion and degradation of materials, such as pipeline steel, have a strong effect on both the environment and the economy. The quantification of these processes can therefore provide important information needed to manage their impact. In this study, a concept for the characterization and quantification of corrosion is demonstrated on API X70 steel immersed in 3.5 wt.% NaCl solution. Due to the difficulty of quantifying corrosion rates, e.g., through single mean values, a unique system is applied that directly couples Raman spectroscopy with vertical scanning interferometry to assess the physical and chemical aspects of steel corrosion kinetics. Vertical scanning interferometry allows the quantification of the topographical evolution of corrosion product formation and material dissolution in combination with the direct measurements of the respective rates. The Raman spectroscopy provides additional information about the (mineral) phases. Rate variations ranging from uniform corrosion to areas of high pit densities are quantified and analyzed in rate maps and subsequently visualized in rate spectra. The rate distribution is classified into different domains and pitting rates. Thus, a comprehensive quantitative assessment of the characteristic corrosion behavior is discussed.