EFFECT OF POTENTIAL ON THE CORROSION FATIGUE CRACK-GROWTH RATE OF FE-AL-MN ALLOY IN 3.5-PERCENT-NACL SOLUTION

The corrosion fatigue crack growth (FCG) behavior of the austenitic Fe-8.87 Al-27.9Mn-1.04C alloy in 3.5 wt% NaCl solution has been investigated. Corrosion fatigue crack growth rates at different electrochemical potentials were measured using compact tension specimens (CTS) at room temperature. The potentials applied ranged from -200 to -1200 mV(SCE), which included the transpassive, passive, and open-circuit potential (E(op)), and cathodic potentials. Sinusoidal loads at an R ratio of 0.1 are applied with frequencies of 1.0, 5.0, and 10 Hz. The results indicated that the FCG rates depend on the frequency and applied potential. The environmental effect became evident as the testing frequency decreased from 10 to 1.0 Hz. The FCG rates were decreased as the applied potential fell in the cathodic region. The FCG rates could be decelerated when the potential is in the passive potential. However, the FCG rate was slower at -200 mV(SCE) (transpassive region) than at E(op). A possible explanation for this observation was discussed in this study.