Potentiodynamic anodic polarisation and dynamic electrochemical impedance spectroscopic (DEIS) measurements were carried out on type 316L stainless steel (SS), alloys 33 and 24 in natural sea water environment in order to assess pitting corrosion resistance. The results revealed that the pitting corrosion resistance was higher in the case of alloys 33 and 24 than 316L SS; due to the higher contents of nitrogen, chromium and molybdenum. DEIS measurements were performed over a wide range of potentials covering the corrosion potential, passive region, breakdown region and dissolution region. It was shown that the impedance measurements in potentiodynamic conditions allow simultaneous investigation of changes in passive layer structure. The impedance spectra of various potential regions were also discussed. The Nyquist plots were fitted using non-linear least-square (NLSS) method for different potential regions.