Cathodic-polarization effects on the long/short corrosion-fatigue crack growth rate of an offshore steel

We study the cyclic crack growth rate of an offshore steel. Compact specimens with long cracks and cylindrical specimens with short surface cracks were tested in air (at frequencies of 5-10 Hz) and in a 3.5% aqueous solution of NaCl (0.2 Hz). In the presence of cathodic polarization (-950mV/SCE), the growth rate of long cracks is higher than under the conditions of free corrosion. The plateau appearing in this case in the da/dN-DeltaK diagrams indicates the presence of hydrogen embrittlement. For DeltaK > 10 MPa, the growth rates of short and long cracks coincide.