The effect of cyclic loading on smooth and pre-pitted type 316LN stainless steel and its weldment in acidified chloride environment is investigated in this study. The onset of fatigue cracks at the bottom of the pit is brought on by the maximum stress concentration effect in acidified chloride environment. Pre-pitted specimens exhibit a more pronounced fatigue life reduction compared to smooth specimens at lower stress amplitudes. The growth of a microscopic crack from an artificial pit, which is influenced by the combined effects of the pit electrolyte and stress concentration factor, is vital for maintaining structural integrity.