Critical Pitting Temperature Research Articles

Study of Effects of Post-Weld Heat Treatment Time on Corrosion Behavior and Manufacturing Processes of Super Duplex Stainless SAF 2507 for Advanced Li-Ion Battery Cases.

Lithium-ion batteries are superior energy storage devices that are widely utilized in various fields, from electric cars to small portable electric devices. However, their susceptibility to thermal runaway necessitates improvements in battery case materials to improve their safety. This study used electrochemical analyses, including open-circuit potential (OCP), potentiodynamic polarization, and critical pitting temperature (CPT) analyses, to investigate the corrosion resistance of super duplex stainless steel (SAF 2507) applied to battery cases in relation to post-weld heat treatment (PWHT) time. The microstructure during the manufacture, laser welding, and PWHT was analyzed using field-emission scanning electron microscopy, X-ray diffraction, and electron backscatter diffraction, and the chemical composition was analyzed using dispersive X-ray spectroscopy and electron probe micro-analysis. The PWHT increased the volume fraction of austenite from 5% to 50% over 3 min at 1200 °C; this increased the OCP from -0.21 V to +0.03 V, and increased the CPT from 56 °C to 73 °C. The PWHT effectively improved the corrosion resistance, laying the groundwork for utilizing SAF 2507 in battery case materials. But the alloy segregation and heterogeneous grain morphology after PWHT needs improvement.

The kinetics of pitting corrosion in a defect-contained Hastelloy X alloy fabricated by laser powder bed fusion

The kinetics of pitting corrosion for Hastelloy X alloys fabricated by laser powder bed fusion (LPBF) were investigated in chloride-containing solutions and critical pitting temperature (CPT) was clarified via electrochemical tests and long-term quasi-in-situ monitoring. A decrease in CPT was verified for LPBF Hastelloy X alloys with an increased defect density in 1 M NaCl solution. Lack of fusion (LOF) defects were more susceptible to metastable pitting nucleation than gas pores, and the corrosion pits nucleated at the LOF defects grow in both pit volume and surface area, leading to a rapid corrosion propagation channel formed along the LOF structure.

Understanding the potentiodynamic critical pitting temperature

To better understand the potentiodynamic critical pitting temperature (CPT), the critical conditions of potential (E) and temperature (T) for repassivation of one-dimensional artificial pits at small depth (x) were investigated. Apart from repassivation resulting from excessive dilution of the pit solution, repassivation underneath the salt film was also observed. The critical conditions for repassivation in (E, T, x) space exhibit a complex functionality. The potentiodynamic-CPT should correspond to the lowest temperature of the critical (E, T) conditions for repassivation of metastable pits, and it represents a critical temperature below which salt precipitation at any potential leads to repassivation of metastable pits.

Effects of Passivation with Cu and W on the Corrosion Properties of Super Duplex Stainless Steel PRE 42

Carbon steel is subjected to several pretreatments to enable its use in highly corrosive environments, such as marine structures. However, its surface treatment is problematic owing to various processes, and these problems can be solved by replacing it with super duplex stainless steel (SDSS), which exhibits remarkable strength and corrosion resistance owing to its austenite and ferrite phases. EN 1.4410 and EN 1.4501 are the most extensively used SDSS grades in marine structures, as they exhibit exceptional strength and corrosion resistance in seawater. This study subjected EN 1.4410 and EN 1.4501 samples to specific heat treatment after casting and observed their structural alterations through field emission scanning electron microscopy. Their passivation states, with or without the Cu and W layers, were determined by examining their corrosion properties through open-circuit potential measurements, electrostatic polarisation tests, electrochemical impedance spectroscopy (EIS), and critical pitting temperature (CPT) analysis. The inclusion of Cu significantly improved the uniform corrosion resistance within the passivation layers, whereas the addition of W enhanced the pitting resistance (Epit, CPT). Additionally, the EIS analysis confirmed a double-layer structure in the passivation layer of EN 1.4501. Moreover, Cu did not act as a strengthening element of the passivation layer, whereas W significantly reinforced it.

Influence of ultrafine surface grain size on the passive film chemistry and critical pitting temperature (CPT) in AISI 316L austenitic stainless steel

ABSTRACT Severe shot peening (SSP) was applied to induce a profound surface deformation characterised by the formation of ultrafine-grained structures with an average grain size of 99 ± 5 nm on AISI 316L. The impact of these ultrafine-grains on the critical pitting temperature (CPT) was investigated in 3.5 wt.% NaCl solution. Additionally, this study comprehensively explored pit chemistry using electrochemical techniques and mechanistic analyses. Moreover, a comparative investigation of the chemical composition of passive films, developed on severe shot peened (SSPed) samples, was undertaken in contrast to their solution-annealed (SAed) counterparts, employing X-ray photoelectron spectroscopy (XPS). Potentiostatic measurements showed that the mean CPT value was 8.8 ± 0.3 °C for the SAed samples, whereas the SSPed counterparts demonstrated a notably higher CPT, averaging at 13.6 ± 0.5 °C. Insights from pencil electrode measurements revealed shallower pit depths and lower critical current density requirements for passivation in the SSPed sample. Furthermore, the passive films formed on the SSPed samples showed a higher concentration of Cr and Mo. These observations were comprehensively elucidated through effective diffusion equations, leading to a discussion regarding the improved resistance to pitting corrosion exhibited by the SSPed samples, thus shedding light on the pivotal role of surface grain refinement in corrosion behaviour improvements.

The effect of surface roughness on re-passivation and pitting corrosion of super duplex stainless steel UNS S 32760

Stainless steel is used as a battery case material because of its excellent strength and corrosion resistance. Among the stainless steels used in fields requiring superior corrosion resistance, duplex stainless steels, composed of austenite and ferrite, exhibit improved strength and corrosion resistance. In particular, super duplex stainless steel (SDSS), with a pitting resistance equivalent number (PREN) between 40 and 50, offers excellent strength and corrosion resistance, making it suitable for structural components in various applications. However, the actual corrosion resistance of a material is often lower than its theoretical value, which has led to extensive research efforts to enhance practical corrosion resistance. Recent studies reported atomic-scale measurements of corrosion resistance and identified the influence of atomic layers on corrosion. Corrosion properties were studied by Trinh et al. (2020) and Nilsson (1992) [26]; however, they did not examine the re-passivation of the SDSS. SDSS requires re-passivation because of real corrosion. Although structural stainless steels are processed to achieve surface roughness in the micrometer range and undergo passivation, research on this aspect is still lacking. To enhance the performance of SDSS, research on re-passivation before and after pitting is required. Therefore, this study analyzed the effect of surface roughness variation from 100 to 1000 nm on the corrosion resistance and re-passivation with or without pitting of SDSS. The surface conditions corresponding to different roughness levels were analyzed using field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM), while corrosion resistance was evaluated through open circuit potential (OCP) measurements, potentiodynamic polarization tests, and cyclic polarization tests at 0.6 V (before broken passivation layer) and 1.3 V (after broken passivation layer), as well as critical pitting temperature (CPT) tests. Surface roughness reduces the corrosion potential (Ecorr) and increases the corrosion current density (Icorr) for activation polarization. With passivation, as the surface roughness increased, uniform corrosion decreased, resulting in a stronger passive layer. The surface roughness lowered the OCP and increased the corrosion rate, thereby reducing the corrosion resistance. Therefore, when SDSS is used in an environment prone to corrosion, a surface roughness of less than 100 nm exhibits superior corrosion resistance.

Corrosion resistance and microstructure analysis of additively manufactured 22% chromium duplex stainless steel by laser metal deposition with wire

Microstructure characteristics and pitting corrosion of a duplex stainless steel (DSS) manufactured by laser metal deposition with wire (LMDw) were studied. The layer-by-layer LMDw process resulted in a mixed microstructure of predominantly ferrite with 2% austenite and chromium-rich nitrides, and reheated regions with ∼33% austenite. The high cooling rate of LMDw restricted the distribution of Cr, Mo, and Ni, in ferrite and austenite, while N diffuses from ferrite to austenite. Subsequent heat treatment at 1100 °C for 1 h resulted in homogenized microstructure, dissolution of nitrides, and balanced ferrite/austenite ratio. It also led to the redistribution of Cr and Mo to ferrite, and Ni and N to austenite. At room temperature, cyclic potentiodynamic polarization measurements in 1.0 M NaCl solution showed no significant differences in corrosion resistance between the as-deposited and heat-treated samples, despite the differences in terms of ferrite to austenite ratio and elemental distribution. Critical pitting temperature (CPT) was the lowest (60 °C) for the predominantly ferritic microstructure with finely dispersed chromium-rich nitrides; while reheated area with ∼33% austenite in as-deposited condition achieved higher critical temperature comparable to what was obtained after heat treatment (73 and 68 °C, respectively). At temperatures above the CPT, selective dissolution of the ferrite after deposition was observed due to depletion of N, while after heat treatment, austenite preferentially dissolved due to Cr and Mo concentrating in ferrite. In summary, results demonstrate how microstructural differences in terms of ferrite-to-austenite ratio, distribution of corrosion-resistant elements, and presence of nitrides affect corrosion resistance of LMDw DSS.

Statistical Distribution of Critical Pitting Temperature of Stainless Steels

The range of Critical Pitting Temperature (CPT) for five different stainless steels is measured to determine whether it is wide or narrow. The impact of bulk solution composition and surface passivation on CPT was also measured in order to evaluate the relative importance of pit initiation and pit propagation on CPT. The results of the study revealed that CPT can be measured within a narrow range (±1.3 °C) regardless of the alloy and bulk solution composition. It is also shown that experimental error caused by crevice corrosion can lead to a wider range of CPT values. These results are explained using the Salinas-Bravo and Newman CPT model. It is shown that, for the conditions studied herein, CPT is not dependent on pit initiation, but rather, it is a transition phenomenon, i.e., CPT is determined by the transition from metastable to stable pit growth.

Microstructure and corrosion performance of high-entropy alloy and austenite and super duplex stainless steels in 3.5% NaCl solution

Stainless steel (STS) has good strength and corrosion resistance. However, it is not suitable for use in deep water because it is vulnerable to low-temperature brittleness. High-entropy alloys (HEAs) are suitable for use in the deep sea because they have low-temperature twins and passivation layers formed by Cr. In this study, to select a suitable material for use as a structural material, the electrochemical properties of a high-entropy alloy and stainless steel were analyzed for comparative evaluation of their corrosion resistance. The potentiodynamic polarization and critical pitting temperature (CPT) were determined to evaluate the corrosion resistance of the passivation layer. The corrosion resistance of STS differed according to the type, whereas the corrosion resistance of the HEA decreased after pressing. Among the STS samples, SDSS2507 was more suitable for use in seawater than STS304L or STS316L. Despite the low corrosion resistance of the HEAs in surficial seawater, they are suitable for use in deep seas where the Cl ion concentration is low.

Influence of the machined surface roughness on the pitting behavior of 304 stainless steel

AbstractThe relationship between specimens with different machined surface roughness and pitting resistance was explored using the critical pitting temperature (CPT), critical pitting potential (Ep), and FeCl3 pitting immersion tests. Compared with the arithmetic mean deviation of the surface contour (Ra), the depth–width ratio could characterize the mathematical relationship between the machined surface roughness and pitting parameters more simply. With an increase in the depth–width ratio, the CPT and Ep of 304 stainless steel decreased, the average corrosion rate increased, the number of pits decreased, and the pit sizes increased. A larger depth–width ratio led to a larger effective diffusion length of metal cations in the pits, thus, the critical pitting criteria could be reached easily, which resulted in the reduction of the pitting resistance of 304 stainless steel.

Critical Pitting Temperature of Stainless Steel: Deterministic Vs. Probabilistic Behavior

The concept of the critical pitting temperature (CPT), which is described as the temperature below which stable pits are not formed regardless of applied potential and exposure time, has received considerable attention in the literature. Over the past few decades, many attempts have been made to assess the CPT of stainless steel as a function of alloy composition, alloy microstructure, bulk solution composition, and surface roughness. In contrast to the pitting potential, which is known to be probabilistic in nature, CPT is believed by most to be a deterministic phenomenon that can be measured within a few degrees Celsius [1]. This notion has been validated by many authors who have observed a narrow range of CPT for several alloy/environment combinations [2,3]. Some authors have recently challenged this idea by reporting scattered CPT values [4]. This work seeks to determine whether the CPT falls within a narrow or wide temperature range (i.e., is CPT a deterministic or probabilistic phenomenon?).To answer this question, potentiostatic CPT measurements were performed using 1 cm² 904L stainless steel electrodes and an applied potential of 750 mV (Ag/AgCl). Temperature was increased at a rate of 1 °C/min, and the CPT was determined using the temperature at which current density rapidly increased. The CPT of 904L stainless steel was measured in four different conditions to evaluate the effect of bulk Cl⁻ concentration (0.05 and 1.0 M NaCl), passivation in 20 vol.% HNO3, and the presence of a corrosion inhibitor (0.02 M NaNO3).Figure 1 shows a cumulative graph of the CPT values of 904L obtained using the four different conditions. In this graph, n is the number of the n th pitted sample and N is the total number of experiments (i.e., 10). For all test conditions, the CPT was measured within ± 1.8 °C, which is in agreement with the reproducible CPT values reported by others [3]. Figure 1 shows that the CPT of 904L is independent of passivation in HNO₃. Further, decreasing bulk solution aggressiveness from 1.0 M NaCl to 0.05 M NaCl does not result in scattered CPT values. However, some authors have reported a considerably broader range (i.e., ± 10 °C) for the CPT of stainless steel (AISI 316L and 2205), as discussed previously. One possible explanation for their larger reported CPT range is the occurrence of crevice corrosion at the interface of the alloy/inert support (e.g., epoxy mount), which results in an inaccurate CPT measurement. To evaluate this hypothesis, the current density vs. temperature curves for two conditions were compared (see Figure 2). The blue and red curves show potentiostatic polarization results for pure pitting corrosion (i.e., crevice-free CPT measurement) and pitting + crevice corrosion, respectively. The gradual increase of the current density with temperature for the red curve suggests the presence of a crevice at the alloy/epoxy interface, which was confirmed using SEM to characterize the electrode post-polarization. On the other hand, when no crevice corrosion occurs, the current density shows a sudden increase at the CPT.The results of this study reveal that the CPT of 904L can be measured to within ± 1.8 °C, regardless of bulk solution aggressiveness (e.g., 1.0 M NaCl and 0.05 M NaCl solution) or passive state before polarization. This finding is in contrast to what some authors have suggested recently. The scattered CPT values reported in the literature are most likely due to contributions from both pitting + crevice corrosion rather than pitting corrosion alone. Acknowledgments Financial support provided by Natural Sciences and Engineering Research Council of Canada (NSERC) is gratefully acknowledged.

Investigation of the Microstructure Dependence of Critical Pitting Temperature and Pitting Potential in a 2205 Duplex Stainless Steel

Dependence of 2205 duplex stainless steel pitting resistance on its microstructure was investigated using microstructural examinations and potentiodynamic and potentiostatic polarization techniques. An as-received hot-rolled alloy was subjected to different heat treatments to understand how microstructural characteristics individually affect the corrosion resistance in terms of critical pitting temperature (CPT), pitting potential (E pit), and metastable pitting characteristics. Results revealed that there is a transition temperature interval for the 2205 DSS. By promoting pit initiation and pit propagation, the Widmanstätten structure significantly deteriorated both CPT, by 10 °C, and E pit, compared to the as-received hot-rolled specimen. The σ phase appearance was also associated with a minor drop in CPT, but a considerable reduction in E pit as it increased the occurrence frequency of metastable pits. The specimen having equiaxed grains had the highest CPT, underwent stable pitting at 47 °C, but still it had a low E pit compared to the hot-rolled specimen due to its higher occurrence frequency of metastable pits. The formation of the Widmanstätten austenite needles weakened the ferrite phase in terms of the pitting resistance by reducing the contents of Cr and Mo in it and made it more susceptible to pit propagation.

Technical Note: Electrochemical Testing for Pitting Corrosion Above Ambient Temperatures Using the Syringe Cell

The syringe cell method has been further developed to evaluate the temperature dependence of pitting corrosion in passive alloys that pit above ambient temperature without artifacts associated with crevice corrosion. The pitting potential of commercially available duplex stainless steel type 2205 was measured at different temperatures by using a hot plate to heat the specimen. Breakdown potentials decreased by about 1 V at test temperatures above 50°C. The critical pitting temperature (CPT) of the alloy was determined to be between 54°C and 59°C by scanning the temperature of the specimen surface during constant potential holds. In all experiments, pits were observed in the area defined by the electrolyte droplet in contact with the specimen surface. Using a more conventional approach mentioned in ASTM Standard G48 Method C, the CPT of the alloy was determined to be 55°C.

Evaluation of 475 °C embrittlement in UNS S32750 super duplex stainless steel using four-point electric conductivity measurements

One of the consequences of the 475 °C embrittlement of duplex stainless steels is the reduction of the resistance to localized corrosion. Therefore, the detection of this type of embrittlement before the material exhibits significant loss in toughness, and corrosion resistance is important to ensure the structural integrity of critical components under corrosion threats. In this research, conductivity measurements are performed using the alternating current potential drop (ACPD) technique with using a portable four-point probe as a nondestructive evaluation (NDE) method for detecting the embrittlement in a 2507 (UNS S32750) super duplex stainless steel (SDSS) aged at 475 °C from as-received condition to 300 h. The electric conductivity results were compared against two electrochemical tests namely double loop electrochemical potentiokinetic reactivation (DL-EPR) and critical pitting temperature (CPT). Mechanical tests and the microstructure characterized using scanning electron microscopy (SEM) imaging are conducted to track the progress of embrittlement. It is shown that the electric conductivity correlates with the changes in impact energy, microhardness, and CPT corrosion tests result demonstrating the feasibility of the four-point probe as a possible field-deployable method for evaluating the 475 °C embrittlement of 2507 SDSS.

Critical pitting temperature of selective laser melted 316L stainless steel: A mechanistic approach

The critical pitting temperature (CPT) of selective laser melted (SLM) 316 L stainless steel in 1.0 M NaCl was measured and compared with a commercial wrought alloy. Potentiostatic measurements determined a mean CPT value of 16 ± 0.7 °C, 27.5 ± 0.8 °C and 31 ± 1 °C for the wrought alloy, the SLM alloy normal to the build direction and parallel to the build direction, respectively. The lead-in pencil electrode technique was used to study the pit chemistry of the two alloys and to explain the higher CPT values observed for the SLM alloy. A lower critical current density required for passivation in a simulated pit solution was measured for the SLM alloy. Moreover, the ratio of the critical concentration to saturated concentration of dissolving metal cations was found to be higher for the SLM alloy, which was related to its different salt film properties, possibly as a result of the SLM’s distinct microstructure.

Comparison Between Stainless Steels and Nickel Alloys Through Pitting Corrosion Resistance Electrochemical Tests

Critical pitting temperature (CPT) is one of the most accepted criteria for alloy classification concerning pitting corrosion. The techniques used nowadays to determine CPT have different parameters for alloys of different material classes, preventing the comparison between stainless steels and nickel based alloys. This study aims to compare the corrosion resistance of nickel based alloys and stainless steels with high corrosion resistance through potentiostatic tests for CPT determination, using a 3M MgCl2 aqueous solution. CPT values were effectively determined for the stainless steels studied but the technique did not have the same efficiency for nickel based alloys due to the occurrence of crevice corrosion, even considering the higher PRE of nickel based alloys.

Pitting Corrosion Characteristic Depending on Welding Pass and Heat Input of GTA Weldment on Superaustenitic Stainless Steel(UNS S32654)

This study investigated the corrosion characteristics of weldments on superaustenitic stainless steels for various heat inputs and numbers of welding passes during gas tungsten arc welding(GTAW). The heat input was changed to 0.7 or 1.4 kJ/mm and the weldment microstructure and chemical composition were analyzed. The weldment corrosion resistance was evaluated by potentiodynamic polarization, and the critical pitting temperature (CPT) was determined. The CPT dropped from 85 to 55 ℃ with both increasing heat input and number of welding passes. The microstructural and chemical compositional analyses revealed that the Mo segregated and precipitated in the interdendritic region, and that the Mo content in the dendritic core was lower than that in the surrounding area. The Mo content decreased when the pitting corrosion initiated. The precipitate content and dendrite core size both increased, and the pitting corrosion resistance decreased with both increasing heat input and number of welding passes. Key words: Superaustenitic stainless steel, 654SMO, Critical pitting temperature, Heat input, Welding pass, GTA welding

Temperature evolution, phase ratio and corrosion resistance of duplex stainless steels treated by laser surface heat treatment

• Laser surface heat treatment (LSHT) was performed on duplex stainless steels 2304, 2205, and 2507. • The effect of laser spot size and cooling time t 12/8 was investigated by numerical simulation and microstructure analysis. • LSHT obtained the peak temperature, the t 12/8 and the effective depth as 1350 °C, 8.9 s and 1.5 mm respectively. • Austenite percentage increased from 2%, 5%, and 38% to 27%, 36% and 55 % respectively for 2304, 2205, and 2507. • LSHT increased the corrosion pitting temperature from 13, 42 and 66 °C to 19, 52 and 76 °C respectively for 2304, 2205, and 2507. Duplex stainless steels (DSS) are promising materials due to excellent corrosion resistance and good mechanical properties. However, the corrosion resistance of DSS welded joints deteriorates unavoidably due to the unbalanced phase ratio, namely a low austenite percentage resulted from the welding thermal cycle. Laser surface heat treatment (LSHT) exhibits tremendous advantages to restore the corrosion resistance especially regarding efficiency and flexibility. By adjusting laser energy input, including laser power and spot size, different LSHT conditions were applied to DSS 2304, 2205 and 2507, whose austenite content were deliberately decreased to a very low percentage. The temperature evolution during the LSHT was calculated out by finite element analysis. Critical pitting temperature (CPT) was measured to evaluate the corrosion resistance. A long length of laser spot and a slow scanning speed were beneficial for increasing the austenite percentage during the LSHT. With the length of laser spot as 100 mm and the scan speed as 2 mm/s, the laser power was adjusted to obtain a target peak temperature of 1350 ℃, which provided a cooling time t 12/8 as 8.9 s and an effective action depth as 1.5 mm. For DSS 2304 and 2205, the austenite percentage increased from 2% and 5% in deteriorated samples to 28 % and 56 % after the LSHT; the CPT increased from 12.5 and 42.3 ℃ to 19.2 and 51.8 ℃ respectively. DSS 2507 remained the highest austenite percentage after the same deterioration and exhibited the best corrosion resistance under all the used conditions. The influence of LSHT processing parameters and material compositions on the phase transformation and the corrosion resistance was discussed accordingly.

Effect of temperature on the electrochemical pitting corrosion behavior of 316L stainless steel in chloride-containing MDEA solution

Here, the effect of temperature on the electrochemical corrosion of 316L stainless steel (SS) in methyl diethanolamine (MDEA) solution with/without 1.0 wt% NaCl in the presence/absence of CO2 was investigated using potentiostatic polarization, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). The electrochemical measurements showed that although the MDEA solution was highly basic, both chloride and temperature played greater roles in the pitting corrosion of 316L SS, similar to plain NaCl solution. The critical pitting temperature (CPT) of 316L SS in MDEA solution with 1.0 wt% NaCl decreased from 67.2 °C to 59.6 °C, and the breakdown potential underwent a negative shift of approximately 400 mV, and the EIS Bode impedance decreased. Furthermore, the breakdown potential shifted negatively with increasing temperature when the temperature was lower than CPT in the MDEA solution containing Cl−; however, the breakdown potential decreased slowly, and its temperature dependence was unclear when the temperature was higher than the CPT. In addition, the passive film resistance of 316L SS in all MDEA solutions decreased as the temperature increased. Particularly for the MDEA solution containing Cl−, the passive film resistance decreased by one order of magnitude when the temperature increased from 50 °C to 60 °C. Although the presence of CO2 in the MDEA solution decreased the passive film resistance, it seemed to reduce the individual corrosion contribution of Cl−. The pitting corrosion process of 316L SS in MDEA solution containing chloride ions was discussed by combining these results with classical pitting mechanisms of stainless steel.

Influence of microstructural morphology on pitting corrosion resistance of duplex stainless steel weld metals

ABSTRACT The formation mechanism of microstructure of duplex stainless steel weld metals with different N content and heat input and the effects of microstructural factors on pitting corrosion resistance of them were investigated. As N content of weld metal increased, ferrite content decreased and Cr nitride content increased. However, once N content exceeded a certain value, Cr nitride content decreased. As the ferrite content of the weld metal decreased, the critical pitting temperature (CPT) increased, and as N content increased, CPT increased. Thus, the pitting corrosion resistance of duplex stainless steel weld metals must be affected by both of N content and Cr nitride, and the precipitation of Cr nitride must also be affected by N content and the ferrite content due to N content and the weld heat input. The results indicated that these microstructural factors were an important index to evaluate the pitting corrosion resistance of duplex stainless steel weld metals.