Corrosion And Passive Behaviour Of Super Duplex Stainless Steel 2507

2507 super duplex stainless steel gradually displaced austenitic stainless steel 304 / 304 L, 316 / 316 L to become important marching mateiral of some key equipment and parts. How is the corrosion resistance in environments of duplex stainless steel is one of the problems to be considered first in application. Study about the corrosion behavior of 2507 super duplex stainless steel in actual situation has provide theoretical guidance for widen the range and fields of applications.The effect of inorganic anions, temperature and p H value on the corrosion behavior and passivation performance of 2507 duplex stainless steel was studied by weight-loss method and electrochemical method.The corrosion rate of austenitic stainless steel and dulex stainless steel is about 10-1 mm/a, 10-3 mm/a respectively, which differed two orders of magnitude, indicating that the pitting corrosion resistance of austenitic stainless steel Obviously weakened, while the standard duplex stainless steel 2205 and super duplex stainless steel 2507 remains excellent resistance to pitting corrosion. So, duplex stainless steel can be used as candidate materials of equipment which was running in situaltion with the concentrations of Cl^- was 0.5 M.With the addition of 0.05 M HCO3- and 0.05 M SO₄^2- in 0.5 M Cl^- solution, pitting potential increased, passive current density decreased, polarization resistance value increased and the donor or acceptor level density decreased, which suggested conductive of passive film decreased and the performance of corrosion resistance increased. HCO₃^- or SO₄^2- can reduce sensitivity to pitting corrosion of UNS S32750 duplex stainless steel in chloride solution. However, when concentration of HCO₃^- in solution increased?> 0.05 M?, adsorption of HCO3- in the interface would also increased, leading to the generation of Fe CO3 and Fex?OH?y?CO3?z which had loose structure and lower densification. Using point defect model?PDM? can be well described the effect of HCO3- concentration on the semiconductor properties of passive film. With the increase of HCO3- concentration in Cl^- solution, donor level density of passive film increased, point defects diffusion coefficient increased, indicating increase of HCO3- concentration will lead to an increase of defect in passive film and the diffusion rate of defects, corrosion resistance of passive film on 2507 duplex stainless steel in solution decreased.With the increase of temperature and decrease of p H value, donor levels density of passive film and point defect diffusion coefficient increased. It was also found that 2507 duplex stainless steel was more sensitive to temperature. It was not suitable to use 2507 duplex stainless steel as a machining material in the situation with high temperatures?above 60 ?? and high concentrations of Cl^-.