As the most common failure mechanism in industry, corrosion of materials costs hundreds of billions of dollars annually to the U.S. economy.1 It is critical to implement optimal corrosion control practices to improve lifecycle and asset management. Accelerated corrosion tests can substantially increase the measurement speed compared to those carried out in natural weathering. Laboratory corrosion tests that closely simulate the atmospheric effects on the corrosion mechanism of materials significantly facilitate the quality control and R&D of new materials and protective coatings for applications in aggressive environments.
The mechanical properties of materials deteriorate during the corrosion process. For example, lepidocrocite (g-FeOOH) and goethite (a-FeOOH) form in the atmospheric corrosion of carbon steel. Their loose and porous nature results in absorption of moisture and in turn further acceleration of the corrosion process.2 Akaganeite (b-FeOOH), another form of iron oxyhydroxide, is generated on the steel surface in chloride-containing environments.3 Nanoindentation can control the indentation depth in the range of nanometers and microns, making it possible to quantitatively measure the hardness and Young’s modulus of the corrosion products formed on the metal surface (Figure 1). It provides physicochemical insight in the corrosion mechanisms involved so as to select the best candidate material for the target applications.