Effect of Cathodic Protection Potential on Corrosion Fatigue Crack Growth of High-Tensile Strength Steel in Synthetic Sea Water

Abstract

Corrosion fatigue crack growth rate (da/dN) of 80kgf/mm2 grade high strength steel HT80 has been investigated in synthetic sea water under the open circuit, anodic and the various cathodic potentials at a frequency of 0.17Hz.The effect of cathodic potential on da/dN as a function of 4K or 4Keff was examined and the crack closure effect caused by corrosion reaction products within crack was discussed.The arrangement by the effective stress intensity factor range 4Keff, which was taken from the crack closure effect of white cathodic reaction deposits (a mixture of CaCO3, MgCO3 and Mg(OH)2), was useful to evaluate the influence of cathodic potential on the crack propagation.The daldN under the cathodic protection potential of -0.7-0.9V (Ag/AgCI) became smaller than that in open circuit, while cathodically polarized potential more negative than -1.0V gave rise to the large acceleration of crack growth rate due to hydrogen embrittlement.