Sigma phase leads to deterioration of corrosion resistance of super duplex stainless steels (SDSS) and its volume fraction increases as the time which the materials is exposed in determined temperature increases. In the present study, the effect of the short aging time on the formation of the sigma phase and on the corrosion behavior of UNS S32520 SDSS at 3.5% sodium chloride solution was evaluated using microstructural characterization, linear potentiodynamic polarization curve and electrochemical impedance spectroscopy. The results indicated that the SDSS sample solution-treated at 1150ºC and aged at 850ºC for 5 min may improve the corrosion resistance in comparison with the as-received and solution-treated conditions, due to the better partition of the elements Cr, Mo and dissolution of certain amount of sigma phase in the microstructure. However, results also showed that when SDSS solution-treated at 1150ºC is aged at 850ºC with the aging time slightly superior (10 min), the precipitation of sigma phase increases leading to a rapid deterioration of the corrosion resistance of the material.

Corrosion of AA7075-T73 aluminum alloy during machining process was studied. An experimental device was proposed in order to simulate machining procedure. A design of experiments - DOE was used in order to evaluate what process parameter is significant. Some electrochemical tests based on open-circuit potential vs time measurements and potentiodynamic polarization were performed in machining fluid of low and high chloride concentrations. Results from DOE showed that the chloride concentration in machining fluid and the presence or not of a zinc coating on the bench vice jaw material in the machining system, along with the interaction between these both factors are significant. OCP results showed oxide growth with time in low and high chloride concentration machining fluid. Passivity breakdown was only observed in high chloride concentration machining fluid. Best fitted parameters were applied to a large scale aeronautical manufacturing company, achieving 95 % reduction in corrosion appearance on the manufactured parts.

The work aims the study of the corrosion behavior of nitride plasma-assisted PVD coated Ti-6Al-4V alloy in 2 M NaOH at 25 and 60°C, using open-circuit potential (OCP) versus time measurements, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The uncoated Ti-6Al-4V alloy showed a passive behavior. The TiN and TiAlN/TiAlCrN coated Ti-6Al-4V alloy also presented a passive behavior and the corrosion potential remained at the same range when compared with the potential of the uncoated alloy. The TiN hard coating showed a superior corrosion resistance, which was evidenced by lower corrosion current densities and higher impedance values. The increase in temperature decreased the corrosion resistance of both uncoated and coated alloy in NaOH.