Cathodic Protection against Propagation of Corrosion Fatigue Cracks of a Mild Steel

Abstract

Fatigue tests of pre-cracked specimens of a mild steel have been conducted in 1%NaCl solution at various cycle frequencies, and an application basis of cathodic protection to decrease crack propagation rate and the damage due to hydrogen embrittlement have been discussed. The efficiency of cathodic protection depends extraordinarily upon stress cycle frequency. At a high cycle frequency the application of cathodic protection does more harm than good. The benefit of cathodic protection can be expected at a frequency lower than 100 c/min. However, there exists an optimum potential for cathodic protection, that is E =-0.8 V vs. SCE, to suppress the crack rate in corrosive environment. The application of excess cathodic current which was beneficial in a smooth specimen should be avoided to prevent corrosion fatigue of a cracked material even if it is ductile.