Effects of Fe and Al ions during hydrogen sulphide (H2S)-induced corrosion of tetracalcium aluminoferrite (C4AF) and tricalcium aluminate (C3A)

Highlights: • Based on multiple investigations, the effects of Fe and Al ions in C₄AF and C₃A corroded by H₂S were clarified. • In C₄AF, Fe ions acted as catalysts for elemental S oxidisation under an H₂S-rich corrosion condition. • AlO_x moieties in C₃A were modified by H₂S, resulting in microstructure degradation. With high concentration and toxic H₂S gas found in sewage facilities, it has ultra-high leakage risk and great environment impact, once the sealing material failure. In this study, hydrogen sulphide (H₂S)-induced corrosion effects of tetracalcium aluminoferrite (C₄AF) and tricalcium aluminate (C₃A) phases of cement were evaluated during the initial stages of reaction. Both phase changes and bond structures were examined by techniques including Fourier transform infrared spectroscopy (FTIR). The results indicate that corrosion occurred through a stepwise reaction promoted by Fe ions. The effects of Fe and Al ions were further quantitatively investigated by X-ray photoelectron spectroscopy (XPS) and ²⁷Al solid-state nuclear magnetic resonance (SSNMR). Compared with hydrated samples, the Fe ions were changed with Fe(II) ions increasing and Fe(III) ions reducing, and the AlO_x group was observed to be transformed form AlO₄ to AlO₆ after H₂S corrosion. Changes obtained will be benefit the further development of hazardous H₂S control material and risk management operations.