Corrosion and Cracking Behavior of the API X-52 and API X-65 Steels with Cathodic Protection

摘要

Cathodic protection is one of the most useful methods to stop corrosion when the deterioration process has started. When applying cathodic protection, the efficiency of this protection method under different experimental conditions is always a concern. High pH environments generally induces stress corrosion cracking (SCC) phenomena which occurs only in a relatively narrow cathodic potential range in the presence of a carbonate/bicarbonate compounds and for pH's greater than 9. In this work, the resistance to the stress corrosion cracking, of the API X-52 and API X-65 steels, was investigated using a modified wedge opening loading (WOL) fracture mechanics specimens. The specimens were loaded with 95% of the yield strength. The resistance of crack growth and the corrosion were evaluated under different protection potentials (-850 and -650 mV). The used electrolytes were simulated soils (carbonate-bicarbonate solution). Evidence of crack propagation of the API X-52 and API X-65 steels were obtained by scanning electron microscopy. The results showed susceptibility to SCC on specimens even with cathodic protection. The applied protection potential (-850 mV vs Cu/CuSO_4 electrode) decreases considerably the corrosion rate on the evaluated steels. Out the context, because Stress is one of the three factors influencing SCC.