Effect of inorganic anions on the corrosion behavior of UNS S32750 duplex stainless steel in chloride solution

Abstract

The present study explored the electrochemical behavior of UNS S32750, a super duplex stainless steel which was not commonly researched in previous studies. The effect of bicarbonate (HCO À 3 ) and sulfate (SO 2À 4 ) on the electrochemical behavior of UNS S32750 duplex stainless steel in the chloride (Cl À ) solution was investigated using potentiodynamic polarization, scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS), and Mott-Schottky analysis. The electrochemistry behavior shows that with the addition of HCO À 3 and SO 2À 4 , pitting potential increased and passive current density decreased, indicating that bicarbonate or sulfate can reduce sensitivity to pitting corrosion of UNS S32750 duplex stainless steel in Cl À solution, and film resistance (R 1 ) and lower charge transfer resistances (R 2 ) increased, and the carriers density (N A and N D ) values are about 10 20 cm 3 , and the carriers density decreases. The results may provide theoretical guidance for material-choosing in the wastewater treatment industries containing high chloride concentration such as nonferrous metallurgical wastewater.

Corrosion Performance of 201 low-Nickel Stainless Steel Anchor in Cl–Contaminated Underground Water with Various Concentrations of SO42−and HCO3−

“…− addition in the underground water solutions. 7,[10][11][12] In previous studies, some indices, such as LSI, 18,32 RSI, 18,19 and LSCI, 20 were proposed to estimate the corrosive tendencies of underground water for carbon steels. These indices were calculated from Eqs.…”

“…According to previous studies, Cl − in the underground water aggravated the corrosion of 201 and 304 austenitic stainless steels, 26,33 whereas SO 4 2− and HCO 3 − inhibited the degradation of 304, 316 austenitic stainless steels, and 32750 duplex stainless steels. 7,[10][11][12] Based on the aforementioned information, a parameter that was termed the composite corrosiveness index (CCI), which included the solution pH information, was proposed to evaluate the corrosive tendency of the underground water on the widely applied austenitic and duplex stainless steels, and the CCI can be calculated from Eq. 5…”

“…HCO 3 − and SO 4 2− addition increased the pitting potentials and reduced the corrosion current densities and carrier densities. 10 The corrosion behavior of AISI 304 stainless steel was investigated by Drogowska et al 11 in NaCl solutions with different concentrations of HCO 3…”

“…In general, there was inconsistency in the conclusions regarding the effects of SO 4 2− and HCO 3 − on the corrosion of stainless steels in various underground waters. Many studies 7,[9][10][11][12][13] have indicated that SO 4 2− and HCO 3 − inhibited the pitting corrosion on stainless steels, whereas others 8 have suggested that the two types of anions doped the passive film heavily, and facilitated the pitting growth on stainless steels. 12,14 The discrepancy could be ascribed to the different types of stainless steels and the different solution chemical compositions.…”

Corrosion behaviour of 2205 DSS in the artificial industrial-marine environment

“…As a widely used material presenting high strength and corrosion resistance, the corrosion behaviour for 2205 DSS performed in an oceanic atmosphere containing sulphur element, which was due to pollution from industrialisation, plays an important role in marine industrial development. Previous researches [1,5,8,[15][16][17][18][19] found that if there are acid ions containing sulphur such as SO 4 2− , HSO 3 − , etc. in the solution or a thin electrolyte layer, it will hinder the formation of the passive film of steel, because the sulfides synthesised by the S and metals can reduce the stability of the passive film, thus increasing the sensitivity of pitting corrosion for stainless steels.…”