ABSTRACT
Super duplex stainless steel UNS S-32760 is one of the most commonly used alloys in several industrial applications, due to its high corrosion resistance. However, this characteristic is affected when the alloy is exposed to aggressive environments.
In this work, the effect of temperature on the critical potential of super duplex stainless steel was studied through the implementation of electrochemical techniques such as Cyclic Potentiodynamic Polarization (CPP), and Potentiodynamic-Galvanostatic-Potentiodynamic Polarization (PD-GS-PD) at 25°C,60°C and 80°C in 3.5% w/w NaCl solutions. Moreover, Tafel extrapolation, linear resistance polarization and Electrochemical Impedance Spectroscopy were used to measure corrosion rates. Furthermore, nonelectrochemical techniques such as Optical Microscopy and Scanning Electron Microscopy (SEM) were applied to observe pitting morphology and size.
The results show that an increase in temperature leads to a higher susceptibility to pitting corrosion and to an increased corrosion rate. Alloy critical Potential values were obtained within a range of 0.85 to 0.94 mV for pitting potential and -0.13 to 0.88 mV for repassivation potential. For temperatures around 80oC, the corrosion rates obtained were lower than 22 μm/year at 24 hours.
Keywords
Super duplex stainless Steel UNS S-32760; pitting corrosion; critical potentials; CPP; PD-GS-PD
