The grain boundary of Armco Iron in liquid lithium, under the influence of steady-state creep, was investigated and showed a parabolic time dependence. An observed delay time for the grain boundary attack was correlated with the nucleation of a grain boundary corrosion product. The activation energies for creep and grain boundary penetration kinetics were found to be the same. Grain boundary penetration behavior under the influence of compressional stresses is the same as under the influence of tensile stresses, suggesting that plastic deformation controls the penetration kinetics regardless of the stress state that causes the plastic deformation.