Corrosion Product Identification
X-ray diffraction is a powerful tool for the identification of corrosion products and often supplements information obtained by chemical analysis. For example, Calcite, Aragonite and Vaterite are three distinctly different crystalline structures, but all have the same composition - CaCO3. As a result, chemical analysis would not be able to differentiate among the three polymorphs, but XRD can. Many other common examples exist such as FeO(OH), CuO and Al2O3.
Phase analysis (as opposed to chemical analysis) is of fundamental importance in controlling the devastating effects of corrosion. Variations in pH, temperature, dissolved oxygen and pressure can all play a role in determining which phase forms during a corrosion process. Thus, identifying the exact crystalline form that is present is often the first step in solving the problem.
Among the many areas where identification of corrosion products can be useful are:
• Boiler tubes and pressure vessels
• Flue stacks
• Storage containers and vessels
• Pipelines and valves
• Mechanical components
• Furnaces and surfaces exposed to high temperature