Pitting Corrosion Resistance and Repassivation Behavior of C-Bearing Duplex Stainless Steel

Abstract

The effects of C-substitution for part of the N content, on the pitting corrosion resistance and repassivation tendencies of duplex stainless steels (DSSs) were investigated. For this investigation, normal UNS S32205 containing N only (DSS-N) and the C-substituted DSS (DSS-NC) were fabricated. Microstructural analyses confirmed that the two DSSs had dual-phase microstructures without precipitates, and they possessed similar initial microstructure, including their grain sizes and phase fractions. Polarization and immersion tests performed in concentrated chloride solutions revealed that the DSS-NC was more resistant against stable pitting corrosion and possessed a higher repassivation tendency than the DSS-N. Furthermore, the corrosion pits initiated and propagated to a less corrosion resistant α phase. Polarization tests and corrosion depth measurements conducted in an HCl solution indicated that the DSS-NC exhibited lower galvanic corrosion rate between the α and γ phases than the DSS-N. Therefore, the growth rate of pit embryo was lowered in the DSS-NC, which shifted the potentials for the stable pit initiation and the pit extinction to the higher values.

Corrosion Behavior of Sensitized AISI 304 Stainless Steel in Acid Chloride Solution

“…E p values were determined as the potentials of strong permanent increase of the current density in the passivity region, which indicates a breakdown of the passive film and the onset of the stable pit growth. The higher E p value means the higher resistance to the pitting corrosion [ 3 , 4 , 6 , 19 , 20 , 22 ]. E corr values were determined as the potentials of the transition from the cathodic to the anodic branches.…”

“…The protective passive film on the SS surface ensures high resistance to the uniform corrosion in common oxidation environments, but under special conditions local corrosion forms can be initiated [ 1 , 2 ]. The presence of aggressive substances can evoke local breakdown of passivity and dangerous pitting corrosion [ 3 , 4 , 5 , 6 , 7 ]. An exposure of austenitic SS in the temperature range of 500–800 °C (“critical temperatures”) with consequent slow cooling in the air, e.g., during welding, is related to their susceptibility to another form of local corrosion—intergranular.…”

Improvement of the Corrosion Resistance by Addition of Ni in Lean Duplex Stainless Steels

“…Uniform (or general) corrosion behavior of the LDSSs was examined through polarization tests in a 1 M HCl solution at 40 • C. After the OCP reached a steady state, the potential was scanned at a rate of 0.17 mV s −1 in the potential range for the active-passive transition. Then, the galvanic corrosion rate between the α and γ phases in the LDSS was quantified by measuring the corrosion depth between the two phases [10,17,[23][24][25]. The polished specimens were immersed in a 1 M HCl solution at 40 • C, and after 20 min of immersion, the three-dimensional corroded morphology and the corrosion depth were examined using a surface optical profiler (Wyko NT8000, Veeco, Plainview, NY, USA).…”

Analysing the Effect of Thermal Treatment With an Aid of Brine Quenching on Microstructural Characteristics and Physical Properties of Aisi-304 Plates

“…AISI 304 steel has been widely utilized for corrosion testing. Under the influence of oxidative chemicals, mainly carbide dissolution [16], intergranular corrosion [17], and pitting corrosion [18] have been reported in some previous works. In this work, an attempt has been made to analyze the possible variation of tensile strength, hardness, toughness, and intergranular corrosive phenomena in the AISI 304 steel samples after heat treatment.…”