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Hyuksang Kwon - One of the best experts on this subject based on the ideXlab platform.

  • Effect of Nickel and Tungsten on Repassivation Rate of Stainless Steels in Chloride Solution by Potential Step Chronoamperometry
    Passivation of Metals and Semiconductors and Properties of Thin Oxide Layers, 2020
    Co-Authors: Hyuksang Kwon
    Abstract:

    Abstract The recent development of the method for analyzing Repassivation rate by a rapid scratch test and high field conduction model makes it possible to predict SCC susceptibility more quantitatively but it impossible to distinguish the Repassivation rates with a little difference due to the inaccurate measurement of scratched surface area. From the scratch test and the potential step chrono- amperometry (PSC) test, the function of nickel and tungsten affecting Repassivation rate is explained as blocking the passivation by metal not participating in the formation of passive film and stabilizing the film by molybdenate (MoO42-) with accelerating the dissolution rate of iron by tungsten, respectively. In addition, a PSC test can be approved by a technique for simulating Repassivation rate by the comparison of the results from two tests. The details in test conditions are mentioned in the paper.

  • a study on the localized corrosion and Repassivation kinetics of fe 20cr xni x 0 20 wt stainless steels via electrochemical analysis
    Corrosion Science, 2015
    Co-Authors: Kkochnim Oh, Hyuksang Kwon
    Abstract:

    Abstract Effects of Ni on the film breakdown, Repassivation and dissolution processes of Fe-20Cr- x Ni ( x  = 0∼20 wt. %) stainless steels (SSs) were examined in a chloride. Among the SSs, Fe-20Cr-10Ni is the weakest to meta-stable pitting corrosion, due presumably to the highest defect density in its passive film. Scratch electrode tests reveal that the Repassivation rate of the SSs increases with an increase or a decrease in nickel content from 10 %. Pit growth rate of the SSs decreases with Ni content. However, Fe-20Cr-10Ni alloy forms a pit with the highest aspect ratio, corresponding to its lowest Repassivation potential.

  • effects of si on the Repassivation kinetics and scc susceptibility of stainless steels
    Journal of The Electrochemical Society, 2008
    Co-Authors: Ihsanulhaq Toor, Jaeyoung Kwon, Hyuksang Kwon
    Abstract:

    Effects of Si on the Repassivation kinetics and stress corrosion cracking (SCC) of alloy 304Si were examined by a scratch electrode technique and slow strain rate test in chloride solutions and compared with those of other stainless steels (SSs), 304 and 316L. Repassivation kinetics of these alloys and Fe-20Cr-xSi (x = 0-2) alloy were analyzed in terms of the current density, i(t), flowing from the scratch as a function of the charge density, q(t), that has flowed from the scratch. Passive film initially nucleated and grew according to the place exchange model, and then grew according to a high-field ion-conduction model in which log i(t) has a linear relationship with 1/q(t) with a slope of cBV. The Repassivation rate of Fe-20Cr-xSi (x = 0-2) alloys, evaluated by the cBV value, increased with an increase in Si content. Furthermore, Repassivation rate decreased on the order of 304Si, 316L, and 304. The resistance to SCC of the SSs (304Si, 304, and 316L) measured in 35 wt % MgCl 2 solution at 120°C was in good agreement with those predicted based on the Repassivation kinetics. The beneficial effects of Si on SCC of 304Si SS appears to be associated with the enrichment of Si in the passive film.

  • Repassivation kinetics of zirconium alloys investigated by a scratching electrode technique
    Metals and Materials International, 2008
    Co-Authors: Chanjin Park, Hyuksang Kwon
    Abstract:

    The Repassivation behavior of zirconium alloys in a solution containing 0.1 M H3BO3 and 0.1 M LiOH was examined by means of a rapid scratching electrode technique. The Repassivation behavior of the scratched surface of the alloys varied with time. The place exchange model reveals that at the initial stage of Repassivation (within 10 ms) log i (t) is linearly proportional to q (t) with a slope of 1/K. The high field ion conduction model reveals that after 25 ms log i (t) is linearly proportional to 1/q(t) with a slope of cBV. The cBV value, in particular, which is a measure of the protectiveness and erosion resistance of an alloy, increases when there is an increase in the Nb content of the alloys, as well as in the applied potential and the solution temperature. This result suggests that these parameters can affect the Repassivation rate of zirconium alloy.

  • manganese effects on Repassivation kinetics and scc susceptibility of high mn n austenitic stainless steel alloys
    Journal of The Electrochemical Society, 2007
    Co-Authors: Ihsanulhaq Toor, Kyung Jin Park, Hyuksang Kwon
    Abstract:

    Effects of Mn on the localized corrosion, Repassivation kinetics, and stress corrosion cracking (SCC) of high Mn-N stainless steels (SSs) were examined in chloride solutions and compared with those of type 304 SS. The resistance to pitting corrosion of high Mn-N SSs decreased with an increase in Mn content at the expense of Ni. Repassivation kinetics of the high Mn-N SSs was analyzed by the relationship between the current density i(t) and the charge density q(t) that has flown from the scratch; passive film initially nucleated according to the place exchange model and then grew according to the high-field ion conduction model in which log i(t) vs 1/q(t) has a linear relationship with a slope (cBV). The Repassivation rate of the alloys, analyzed by the (cBV) value, was decreased with an increase in the Mn content. The resistance to SCC of the alloys measured in 25% MgCl 2 was in good agreement with that predicted, based on their Repassivation rate. The deleterious effects of Mn on the localized and stress corrosion of the alloys appear to be associated with an increase in number and size of nonmetallic inclusions such as (Mn, Cr) oxides with Mn content.

J R Scully - One of the best experts on this subject based on the ideXlab platform.

  • Repassivation behavior of individual grain facets on dilute ni cr and ni cr mo alloys in acidified chloride solution
    Journal of Physical Chemistry C, 2018
    Co-Authors: Kateryna Gusieva, Katie Lutton Cwalina, William H Blades, Gopalakrishnan Ramalingam, J H Perepezko, Petra Reinke, J R Scully
    Abstract:

    The effects of crystal orientation and prior etching on the polarization and Repassivation behavior of Ni–Cr and Ni–Cr–Mo alloys have been investigated in acidic chloride environment using dc potentiostatic and ac single-frequency electrochemical impedance spectroscopy. Tests were conducted within the passive region at potentials where local oxide breakdown was possible. Surface morphologies of grains across a wide range of orientations were measured before and after passivation using atomic force microscopy. Oxide growth was monitored on isolated low- and high-index crystallographic planes as a function of Repassivation time, enabling the independent measurement of the oxidation and total anodic current densities. Grains exhibited the tendency to either passivate with significant or minimal oxidation or instead resist active passivation and Repassivation. The oxidation performance was a function of the crystallographic orientation of the exposed grain surface. The oxides grown on various-orientated surfa...

  • Repassivation behavior of individual grain facets on dilute ni cr and ni cr mo alloys in acidified chloride solution c
    The Journal of Physical Chemistry, 2018
    Co-Authors: Kateryna Gusieva, Katie Lutton Cwalina, William H Blades, Gopalakrishnan Ramalingam, J H Perepezko, Petra Reinke, J R Scully
    Abstract:

    The effects of crystal orientation and prior etching on the polarization and Repassivation behavior of Ni–Cr and Ni–Cr–Mo alloys have been investigated in acidic chloride environment using dc potentiostatic and ac single-frequency electrochemical impedance spectroscopy. Tests were conducted within the passive region at potentials where local oxide breakdown was possible. Surface morphologies of grains across a wide range of orientations were measured before and after passivation using atomic force microscopy. Oxide growth was monitored on isolated low- and high-index crystallographic planes as a function of Repassivation time, enabling the independent measurement of the oxidation and total anodic current densities. Grains exhibited the tendency to either passivate with significant or minimal oxidation or instead resist active passivation and Repassivation. The oxidation performance was a function of the crystallographic orientation of the exposed grain surface. The oxides grown on various-orientated surfaces differed in their film growth kinetics, morphology, and steady state thicknesses, even given similar total anodic current densities due to dissimilar oxidation efficiencies. For Ni-11 wt % Cr, only orientations close to (1 0 1) were able to form stable passive films, aided by nanofaceted surfaces with a matchstick-type morphology. On the other hand, all orientations of the Ni-11 wt % Cr-6 wt % Mo alloys formed electrochemically stable oxides films owing to the beneficial influence of Mo on Repassivation. Passivation, breakdown behavior, and oxide properties vary with crystal orientation, and this work provides insight into the effects of crystallographic orientation and oxide film morphology on the passivation mechanism of Ni–Cr and Ni–Cr–Mo alloys.

  • crevice corrosion stabilization and Repassivation behavior of alloy 625 and alloy 22
    Corrosion, 2001
    Co-Authors: B A Kehler, G O Ilevbare, J R Scully
    Abstract:

    Abstract The crevice corrosion resistance of Alloy 625 (UNS N06625) and Alloy 22 (UNS N06022) was compared based on critical potentials for stabilization and Repassivation as well as crevice stabilization rates derived from critical potential data. The effects of temperature and anion composition in 5 M lithium chloride (LiCl) brine-type electrolytes were examined. Repassivation potentials measured at 95°C were similar for both alloys and were not greatly influenced by bulk electrolyte composition, pH, or accumulated anodic charge associated with crevice attack. However, a decrease in temperature increased Repassivation potentials to a greater extent for Alloy 22 in comparison to Alloy 625. Crevice corrosion stabilization properties of Alloy 625 and Alloy 22 were influenced by temperature and electrolyte composition but not bulk solution pH ranging from 2.75 to 7.75. Crevice stabilization occurred at more active critical potentials in 5 M LiCl electrolytes with a molar ratio of chloride ions to total oxya...

  • on the Repassivation behavior of high purity titanium and selected α β and β α titanium alloys in aqueous chloride solutions
    Journal of The Electrochemical Society, 1996
    Co-Authors: D G Kolman, J R Scully
    Abstract:

    The Repassivation characteristics of a titanium thin film evaporated from a high-purity Ti source as well as selected α (commercially pure Ti, Ti-5Al-2.5Sn), β, and β + α titanium alloys (Ti-15Mo-3Nb-3Al, Ti-15V-3Cr-3Al-3Sn, and Ti-3Al-8V-6Cr-4Zr-4Mo) were examined. Both the rapid thin film fracture and scratch depassivation methods were used in aqueous chloride solutions (0.6 M NaCl, 5 M HCl, 5 M LiCl, 5 M HCl + 1 M TiCl 3 ). Bare surface open-circuit potentials followed the relationship E(V SCE ) = -1.20 (pH = 0) - 0.043 pH based on the mixed potential established between the anodic Ti/Ti +3 , Ti/TiO 2 , and water or H + reduction reactions. Oxide formation after depassivation was of low overall current efficiency on all titanium materials ; a large percentage of the anodic charge following depassivation contributed to dissolution. Consequently, an empirical expression was used to describe the anodic current density decay during Repassivation ; i = i o (t/t o ) -m . Potentiostatic current transients on rapidly fractured thin film Ti produced plateau bare-metal i o values greater than 100 A/cm 2 which were below the theoretical ohmic limit, m = 1.0 to 1.4 depending on solution and potential and t o values from 20 to 30 μs. Two anodic Tafel regions and a single cathodic region best described IR-corrected E - log i relationships for bare Ti in all electrolytes. LiCl and TiCl 3 inhibited bare surface dissolution but slightly delayed current density decay. Minimal differences between any of the Repassivation parameters utilized were observed for selected α, β, and β + α titanium alloys. The similarity was attributed to dominance of Ti +3 production in the total anodic charge during Repassivation and predominantly TiO 2 formation in the passivating oxides of all alloys.

  • Repassivation of pits in aluminum thin films
    Journal of The Electrochemical Society, 1996
    Co-Authors: G S Frankel, J R Scully, Christopher V Jahnes
    Abstract:

    The effect of metal film thickness on Repassivation of pits in sputter-deposited Al thin films was investigated in chloride solutions. The Repassivation potential and the critical current density, which is the pit current density below which pits stop growing, were determined for pits in Al thin films ranging from 100 Ǻ to 43 µm in thickness. The Repassivation potential first decreased as thickness increased from 100 to 4350 Ǻ, and then increased as the film thickness increased further. This behavior was found to be a consequence of the pit currentdensity/potential relationship. The critical current density, a more informative parameter, decreased for increasing metal film thickness, even when the Repassivation potential increased. The critical current density is the minimum current density needed to maintain the critical pit environment and prevent Repassivation. The Repassivation potential for a given metal film thickness is the potential at which the pit current density drops below the critical value. Masstransport and ohmic resistance both increase as the metal film thickness increases, but the former enhances pit stability and the latter destabilizes pitting in this system. Pit Repassivation, and thus stability, are strongly influenced by mass-transport considerations for pits in very thin pits, even though dissolution at low potentials is not under pure mass-transport control. Ohmic effects become increasingly important as the film thickness increases.

H Habazaki - One of the best experts on this subject based on the ideXlab platform.

  • Depassivation–Repassivation behavior of a pure iron surface investigated by micro-indentation
    Electrochimica Acta, 2020
    Co-Authors: Takatoshi Yamamoto, Koji Fushimi, H Habazaki, Hidetaka Konno
    Abstract:

    Abstract Depassivation–Repassivation behavior on a pure iron surface in borate buffer solution was examined under potentiostatic control by a micro-indentation test. Current peaks emerge during both downward and upward drives of the indenter due to depassivation which is caused by plastic deformation of the substrate but not elastic deformation and Repassivation. The total electric charge of the current peaks is proportional to the maximum load. The total electric charge also increases with increase in intermission time of the indentation, indicating that the passive film is ruptured even during stress relaxation. It is estimated from the electric charge balance that 82% and 18% of the film rupture occurs during the downward drive and intermission, respectively, and that no rupture occurs during the upward drive. Furthermore, the film-ruptured area is estimated to be 80% of the plastic deformed surface area. The partial retainment of the passive film on iron suggests that the ductility of the passive film is higher than that of the substrate.

  • depassivation Repassivation behavior of a pure iron surface investigated by micro indentation
    Electrochimica Acta, 2010
    Co-Authors: Takatoshi Yamamoto, Koji Fushimi, H Habazaki, Hidetaka Konno
    Abstract:

    Abstract Depassivation–Repassivation behavior on a pure iron surface in borate buffer solution was examined under potentiostatic control by a micro-indentation test. Current peaks emerge during both downward and upward drives of the indenter due to depassivation which is caused by plastic deformation of the substrate but not elastic deformation and Repassivation. The total electric charge of the current peaks is proportional to the maximum load. The total electric charge also increases with increase in intermission time of the indentation, indicating that the passive film is ruptured even during stress relaxation. It is estimated from the electric charge balance that 82% and 18% of the film rupture occurs during the downward drive and intermission, respectively, and that no rupture occurs during the upward drive. Furthermore, the film-ruptured area is estimated to be 80% of the plastic deformed surface area. The partial retainment of the passive film on iron suggests that the ductility of the passive film is higher than that of the substrate.

  • depassivation Repassivation behavior of type 312l stainless steel in nacl solution investigated by the micro indentation
    Corrosion Science, 2009
    Co-Authors: Takatoshi Yamamoto, Koji Fushimi, Shiro Tsuri, Tetsuo Adachi, H Habazaki
    Abstract:

    Abstract Repassivation behavior of type-312L stainless steel containing 6% of molybdenum was examined in NaCl solution using in situ micro-indentation technique, together with type-304 and 316L stainless steels. High stability of the passive film formed on the type-312L stainless steel was also examined by depth profiling analysis of passive films using glow discharge optical emission spectroscopy (GDOES). In 0.9 mol dm −3 NaCl solution at 296 K the type-304 and 316L stainless steels are passive only up to 0.3 V (SHE), above which pitting corrosion occurs. In contrast, no pitting corrosion occurs on type-312L stainless steel. Despite the significant difference of the pitting corrosion resistance, the Repassivation kinetics of the three stainless steels, examined by micro-indentation at 0.3 V (SHE), is similar. The presence of molybdenum in the stainless steel does not influence the Repassivation kinetics. The charge required to repassivate the ruptured type-312L stainless steel surface increases approximately linearly with the potential, even though the passivity-maintaining current increased markedly at potentials close to the transpassive region. Repassivation occurs without accompanying significant dissolution of steel, regardless of the stability of passive state. Depth profiling analyses of the passive films on the type-312L stainless steels formed at several potentials revealed that molybdenum species enrich in the outer layer of the passive film, below which chromium-enriched layer is present. The permeation of chloride ions may be impeded by the outer layer containing molybdate, enhancing the resistance against the localized corrosion of the type-312L stainless steel.

  • Depassivation–Repassivation behavior of type-312L stainless steel in NaCl solution investigated by the micro-indentation
    Corrosion Science, 2009
    Co-Authors: Takatoshi Yamamoto, Koji Fushimi, Shiro Tsuri, Tetsuo Adachi, H Habazaki
    Abstract:

    Abstract Repassivation behavior of type-312L stainless steel containing 6% of molybdenum was examined in NaCl solution using in situ micro-indentation technique, together with type-304 and 316L stainless steels. High stability of the passive film formed on the type-312L stainless steel was also examined by depth profiling analysis of passive films using glow discharge optical emission spectroscopy (GDOES). In 0.9 mol dm −3 NaCl solution at 296 K the type-304 and 316L stainless steels are passive only up to 0.3 V (SHE), above which pitting corrosion occurs. In contrast, no pitting corrosion occurs on type-312L stainless steel. Despite the significant difference of the pitting corrosion resistance, the Repassivation kinetics of the three stainless steels, examined by micro-indentation at 0.3 V (SHE), is similar. The presence of molybdenum in the stainless steel does not influence the Repassivation kinetics. The charge required to repassivate the ruptured type-312L stainless steel surface increases approximately linearly with the potential, even though the passivity-maintaining current increased markedly at potentials close to the transpassive region. Repassivation occurs without accompanying significant dissolution of steel, regardless of the stability of passive state. Depth profiling analyses of the passive films on the type-312L stainless steels formed at several potentials revealed that molybdenum species enrich in the outer layer of the passive film, below which chromium-enriched layer is present. The permeation of chloride ions may be impeded by the outer layer containing molybdate, enhancing the resistance against the localized corrosion of the type-312L stainless steel.

Kateryna Gusieva - One of the best experts on this subject based on the ideXlab platform.

  • Repassivation behavior of individual grain facets on dilute ni cr and ni cr mo alloys in acidified chloride solution
    Journal of Physical Chemistry C, 2018
    Co-Authors: Kateryna Gusieva, Katie Lutton Cwalina, William H Blades, Gopalakrishnan Ramalingam, J H Perepezko, Petra Reinke, J R Scully
    Abstract:

    The effects of crystal orientation and prior etching on the polarization and Repassivation behavior of Ni–Cr and Ni–Cr–Mo alloys have been investigated in acidic chloride environment using dc potentiostatic and ac single-frequency electrochemical impedance spectroscopy. Tests were conducted within the passive region at potentials where local oxide breakdown was possible. Surface morphologies of grains across a wide range of orientations were measured before and after passivation using atomic force microscopy. Oxide growth was monitored on isolated low- and high-index crystallographic planes as a function of Repassivation time, enabling the independent measurement of the oxidation and total anodic current densities. Grains exhibited the tendency to either passivate with significant or minimal oxidation or instead resist active passivation and Repassivation. The oxidation performance was a function of the crystallographic orientation of the exposed grain surface. The oxides grown on various-orientated surfa...

  • Repassivation behavior of individual grain facets on dilute ni cr and ni cr mo alloys in acidified chloride solution c
    The Journal of Physical Chemistry, 2018
    Co-Authors: Kateryna Gusieva, Katie Lutton Cwalina, William H Blades, Gopalakrishnan Ramalingam, J H Perepezko, Petra Reinke, J R Scully
    Abstract:

    The effects of crystal orientation and prior etching on the polarization and Repassivation behavior of Ni–Cr and Ni–Cr–Mo alloys have been investigated in acidic chloride environment using dc potentiostatic and ac single-frequency electrochemical impedance spectroscopy. Tests were conducted within the passive region at potentials where local oxide breakdown was possible. Surface morphologies of grains across a wide range of orientations were measured before and after passivation using atomic force microscopy. Oxide growth was monitored on isolated low- and high-index crystallographic planes as a function of Repassivation time, enabling the independent measurement of the oxidation and total anodic current densities. Grains exhibited the tendency to either passivate with significant or minimal oxidation or instead resist active passivation and Repassivation. The oxidation performance was a function of the crystallographic orientation of the exposed grain surface. The oxides grown on various-orientated surfaces differed in their film growth kinetics, morphology, and steady state thicknesses, even given similar total anodic current densities due to dissimilar oxidation efficiencies. For Ni-11 wt % Cr, only orientations close to (1 0 1) were able to form stable passive films, aided by nanofaceted surfaces with a matchstick-type morphology. On the other hand, all orientations of the Ni-11 wt % Cr-6 wt % Mo alloys formed electrochemically stable oxides films owing to the beneficial influence of Mo on Repassivation. Passivation, breakdown behavior, and oxide properties vary with crystal orientation, and this work provides insight into the effects of crystallographic orientation and oxide film morphology on the passivation mechanism of Ni–Cr and Ni–Cr–Mo alloys.

Takatoshi Yamamoto - One of the best experts on this subject based on the ideXlab platform.

  • Depassivation–Repassivation behavior of a pure iron surface investigated by micro-indentation
    Electrochimica Acta, 2020
    Co-Authors: Takatoshi Yamamoto, Koji Fushimi, H Habazaki, Hidetaka Konno
    Abstract:

    Abstract Depassivation–Repassivation behavior on a pure iron surface in borate buffer solution was examined under potentiostatic control by a micro-indentation test. Current peaks emerge during both downward and upward drives of the indenter due to depassivation which is caused by plastic deformation of the substrate but not elastic deformation and Repassivation. The total electric charge of the current peaks is proportional to the maximum load. The total electric charge also increases with increase in intermission time of the indentation, indicating that the passive film is ruptured even during stress relaxation. It is estimated from the electric charge balance that 82% and 18% of the film rupture occurs during the downward drive and intermission, respectively, and that no rupture occurs during the upward drive. Furthermore, the film-ruptured area is estimated to be 80% of the plastic deformed surface area. The partial retainment of the passive film on iron suggests that the ductility of the passive film is higher than that of the substrate.

  • depassivation Repassivation behavior of a pure iron surface investigated by micro indentation
    Electrochimica Acta, 2010
    Co-Authors: Takatoshi Yamamoto, Koji Fushimi, H Habazaki, Hidetaka Konno
    Abstract:

    Abstract Depassivation–Repassivation behavior on a pure iron surface in borate buffer solution was examined under potentiostatic control by a micro-indentation test. Current peaks emerge during both downward and upward drives of the indenter due to depassivation which is caused by plastic deformation of the substrate but not elastic deformation and Repassivation. The total electric charge of the current peaks is proportional to the maximum load. The total electric charge also increases with increase in intermission time of the indentation, indicating that the passive film is ruptured even during stress relaxation. It is estimated from the electric charge balance that 82% and 18% of the film rupture occurs during the downward drive and intermission, respectively, and that no rupture occurs during the upward drive. Furthermore, the film-ruptured area is estimated to be 80% of the plastic deformed surface area. The partial retainment of the passive film on iron suggests that the ductility of the passive film is higher than that of the substrate.

  • depassivation Repassivation behavior of type 312l stainless steel in nacl solution investigated by the micro indentation
    Corrosion Science, 2009
    Co-Authors: Takatoshi Yamamoto, Koji Fushimi, Shiro Tsuri, Tetsuo Adachi, H Habazaki
    Abstract:

    Abstract Repassivation behavior of type-312L stainless steel containing 6% of molybdenum was examined in NaCl solution using in situ micro-indentation technique, together with type-304 and 316L stainless steels. High stability of the passive film formed on the type-312L stainless steel was also examined by depth profiling analysis of passive films using glow discharge optical emission spectroscopy (GDOES). In 0.9 mol dm −3 NaCl solution at 296 K the type-304 and 316L stainless steels are passive only up to 0.3 V (SHE), above which pitting corrosion occurs. In contrast, no pitting corrosion occurs on type-312L stainless steel. Despite the significant difference of the pitting corrosion resistance, the Repassivation kinetics of the three stainless steels, examined by micro-indentation at 0.3 V (SHE), is similar. The presence of molybdenum in the stainless steel does not influence the Repassivation kinetics. The charge required to repassivate the ruptured type-312L stainless steel surface increases approximately linearly with the potential, even though the passivity-maintaining current increased markedly at potentials close to the transpassive region. Repassivation occurs without accompanying significant dissolution of steel, regardless of the stability of passive state. Depth profiling analyses of the passive films on the type-312L stainless steels formed at several potentials revealed that molybdenum species enrich in the outer layer of the passive film, below which chromium-enriched layer is present. The permeation of chloride ions may be impeded by the outer layer containing molybdate, enhancing the resistance against the localized corrosion of the type-312L stainless steel.

  • Depassivation–Repassivation behavior of type-312L stainless steel in NaCl solution investigated by the micro-indentation
    Corrosion Science, 2009
    Co-Authors: Takatoshi Yamamoto, Koji Fushimi, Shiro Tsuri, Tetsuo Adachi, H Habazaki
    Abstract:

    Abstract Repassivation behavior of type-312L stainless steel containing 6% of molybdenum was examined in NaCl solution using in situ micro-indentation technique, together with type-304 and 316L stainless steels. High stability of the passive film formed on the type-312L stainless steel was also examined by depth profiling analysis of passive films using glow discharge optical emission spectroscopy (GDOES). In 0.9 mol dm −3 NaCl solution at 296 K the type-304 and 316L stainless steels are passive only up to 0.3 V (SHE), above which pitting corrosion occurs. In contrast, no pitting corrosion occurs on type-312L stainless steel. Despite the significant difference of the pitting corrosion resistance, the Repassivation kinetics of the three stainless steels, examined by micro-indentation at 0.3 V (SHE), is similar. The presence of molybdenum in the stainless steel does not influence the Repassivation kinetics. The charge required to repassivate the ruptured type-312L stainless steel surface increases approximately linearly with the potential, even though the passivity-maintaining current increased markedly at potentials close to the transpassive region. Repassivation occurs without accompanying significant dissolution of steel, regardless of the stability of passive state. Depth profiling analyses of the passive films on the type-312L stainless steels formed at several potentials revealed that molybdenum species enrich in the outer layer of the passive film, below which chromium-enriched layer is present. The permeation of chloride ions may be impeded by the outer layer containing molybdate, enhancing the resistance against the localized corrosion of the type-312L stainless steel.