TWI Industrial Member Report Summary 254/1984
By G S Booth and T lwasaki
In air, the fatigue threshold stress intensity factor was similar to that reported in the literature. Under freely corroding conditions the threshold was reduced by approximately 20%, whereas cathodic protection at -850mV (Ag/AgCl) restored the threshold to its in-air value. Crack propagation rates in air were in good agreement with existing data but under free corrosion the growth rate was accelerated by a factor of between 7 and 10, somewhat more than previously observed. The growth rate under cathodic protection was slightly slower than under freely corroding conditions. For corrosion fatigue, it has been shown that a relationship exists between the constants in the Paris growth rate equation, similar to that found in air.