Cathodic protection and the thickness effect. The interactions

Recently additional fatigue results from an Italian collaborative research program have become available, permitting a re-evaluation of both the effect of cathodic protection and the so-called 'thickness effect'. This data defines the fatigue life of 50 mm base member plate-to-plate and tubular joints in both air and sea water with cathodic protection (CP). When combined with previously presented data for 32 mm base member joints, it permits an assessment of the thickness effect for plate-to-plate joints in air and CP, and for tubular joints in CP. The derived thickness effect in air is of similar magnitude to that reported in the literature. However, the thickness effect for the tubular joints appears significantly less than for the T-but in air. The thickness effect associated with crack initiation life and crack propagation life is also derived. It is notable that the thickness effect associated with crack initiation is markedly reduced in the case of the tubular joints with respect to the plate joints. The effeciency of CP in restoring total life is assessed for both types of joints and both thicknesses. Further analysis on the plate-to-plate data allows an assessment of the effect of CP on crack initiation and crack propagation.