In situ Raman spectroscopy study of corrosion products on the surface of carbon steel in solution containing Cl^- and SO₄^2-

Corrosion products of carbon steel in a simulated solution containing Cl^- and SO42- were investigated by in situ Raman spectroscopy with a self-designed device. The results of Raman test and the SEM/EDS analysis of samples in different immersion times indicate that the corrosion products on the surface of the carbon steel consist of double rust layers, i.e. a porous outer layer (lepidocrocite γ-FeOOH) and a compact inner layer (magnetite Fe₃O₄). Aggressive ions such as Cl^- and SO42- promote corrosion leading to the formation of lepidocrocite γ-FeOOH. Weight loss vs. time curve was also measured to study the effects of corrosion products. Corrosion products on a parallel sample were tested by Raman spectroscopy in air environment, which shown a distinct result from the one of in situ test.