Thermal cycles of conventional galvanizing and galvannealing processes were applied to low carbon martensitic steels to examine the mechanical property of martensitic steels after their processing in conventional Continuous Galvanizing Lines (CGL). During the thermal cycle simulation, tempering phenomena occurred resulting in changes of microstructure and mechanical properties. In this study, the tensile deformation behavior of martensitic steels was studied in detail in order to understand the tempering phenomena occurring during their processing. It was found that, after tempering, the strain hardening ability decreased drastically and that the plastic flow became localized. An experimental analysis of this phenomenon will be presented based on TEM microstructural observation and Internal Friction measurements.