In this research, the stainless steel AISI-SAE 630 was studied under two conditions: manufacturing condition and after a thermal treatment, with the purpose of eliminating stress possibly produced during the service time, in an environment simulating the sea water conditions, in order to analyze the behavior of this material under these conditions, during 35 days. the techniques used were spectroscopy of impedances (Eis), cyclical polarization, and differential aeration test and critical pitting temperature (cpt), in order to determine the corrosion rate by pitting, and the cpt. the results showed that the techniques of Eis and Rp are not the most adequate for measuring the corrosion rate by pitting. the test specimen without treatment presented a highest susceptibility to the pitting corrosion with Ep value smaller, which was confrmed by the profle depth, giving as a result a higher rate, probably for absence of tantalum in this material. the cpt for the stainless steel was of 29±1°c, which is very close to the temperature of service, bein this variable (temperature) the cause of the deterioration of the material.