How to determine the severity of HCN-H₂S-H₂O corrosion

Thread Content

Taking into account the background of formation, corrosion morphology, and monitoring methods of HCN-H₂S-H₂O corrosion as described earlier, the severity of corrosion can be assessed comprehensively from the following perspectives: Medium parameter assessment – If the CN⁻ concentration is greater than 500 mg/kg, the H₂S concentration is greater than 50 ppm, and the pH value of the system is less than 6, it indicates that the corrosion activity is in a high-risk range, and corrosion will accelerate rapidly. Corrosion rate assessment: A corrosion rate measured by resistance/inductance probes of >0.5 mm/a, or an annual thinning of the equipment’s wall thickness exceeding 10% of the designed wall thickness, indicates a severe corrosion condition. Corrosion pattern assessment: The appearance of obvious pitting on the equipment surface, hydrogen bubbling, or the detection of microcracks through metallographic testing indicates that corrosion has progressed to a stage where cracking is a risk, which constitutes severe corrosion. Hydrogen permeation assessment: If the hydrogen permeation value measured by the hydrogen flux sensor is greater than 10 ml/(cm²·s), it indicates a very high risk of hydrogen-induced cracking, and corrosion has reached a severe level.