A Study on Flow-Accelerated Corrosion Mechanism of Low Alloy Tip- in Alkaline Solution using Rotating Cylinder Electrode

摘要

Activation and mass transfer process was studiedusing rotating cylinder electrode regarding the flow-acceleratedcorrosion of low alloy steel (ASME SA106 Grade C) in roomtemperature alkaline solution. The reducing agent diffusedeasily as rotating speed increased, and caused corrosionpotential to shift upward. Passive film formed from pH 9.8according to the mechanism of oxidation and subsequentprecipitation of ferrous species. Above pH 10.4, film formationprocess was active and stable. Corrosion current showedincrement with rotating velocity in pH 6.98, while it soonsaturated in above pH 9.8. On the other hand the limiting current,which governs pure mass transfer phenomenon of reducingspecies, increased with the rotating speed regardless of pH value.This indicates that activation reactions, which constituteoxidation of ferrous ion and formation of passive film on thebare metal surface, controls the entire corrosion process.