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The impact of 316L stainless steel discolouration on chloride induced pitting corrosion was quantified. Several degrees of discolouration were produces by chemical passivation, simulated rouging or anodic polarization. Discolouration was characterized by spectral analysis in the visible and NIR range (400-1000 nm). Pitting corrosion resistance was quantified by pitting potential measurements. The spectra were used to indicate whether pitting or transpassive behaviour would occur using chemometric classification techniques with 88% accuracy. In addition, pitting potentials were predicted combining chemometrics and survival analysis techniques with a 90 mV RMS error in cross-validation. XPS analysis linked pitting resistance with the Cr/Fe balance. • 316L surface discolouration can be quantified by Vis-NIR spectral measurements. • The occurrence of pitting was predicted by application of chemometric classification. • The pitting potential was predicted by application of chemometric survival analysis. • Transpassive outcomes are included by combining chemometric and survival regression. [ABSTRACT FROM AUTHOR]

N-lauroylsarcosine sodium is proved to be effective in inhibiting 304 L SS pitting corrosion. Under various elastic tensile stresses, the inhibition behavior of N-LSS on 304 L SS pitting corrosion is studied, and N-LSS increases significantly 304 L SS pitting potential by more than 400 mV. Under small elastic tensile stress (≤16.63 %σ 0.2), the adsorption of N-LSS can inhibit 304 L SS pitting corrosion by enhancing the protection of N-LSS film and specific adsorption effect of N-LSS. Under large elastic tensile stress (≥46.84 %σ 0.2), the decrease of N-LSS adsorption effect reduces the inhibition effect of N-LSS specific adsorption for 304 L SS pitting corrosion growth. • N-LSS could effectively inhibit the initiate and growth of 304 L SS pitting corrosion. • The elastic tensile stress has little effect on 304 L SS pitting corrosion initiation. • The elastic tensile stress can affect the adsorption effect of N-LSS. • Elastic stress affects N-LSS specific absorption on 304 L SS pitting corrosion growth. [ABSTRACT FROM AUTHOR]

Pitting and galvanic corrosion of 2205 DSS with σ phase were investigated in the presence of Pseudomonas aeruginosa. Pitting corrosion was accelerated by σ phase, and further promoted by P. aeruginosa. The σ phase changed the distribution of pitting sites from being concentrated on phase boundaries and α phase in the solution treated coupons to being around σ phase in the biotic medium. The galvanic corrosion between α and γ phases was enhanced by the bacterium, and σ phase led to anodic dissolution of γ phase instead of α phase in DSS with solution treatment. • Pitting corrosion of 2205 DSS is accelerated by σ phase. • Pitting corrosion is further promoted by P. aeruginosa. • Pitting occurs around σ phase due to the initial bacterial attachment. • The α phase corrodes galvanically for DSS with solution treatment. • The σ phase results in the anodic dissolution of γ phase instead of α phase. [ABSTRACT FROM AUTHOR]

Additions of 1–5 wt% W element enhanced corrosion resistance and mechanical properties of LDED-316 SS. Microstructure characterized the grain refinement and precipitation of ferrite and W-Mo carbides. Mechanical tests showed enhanced tensile strength and hardness of 316–5 W by 37.4% and 30.8%, respectively. Electrochemical tests indicated an increasing pitting potential and polarization resistance of 316–3 W in 3.5 wt% NaCl solution by 0.535 V SCE and 1679 kΩ·cm2, respectively. Corrosion morphology showed the preferential dissolution of ferrite and W-Mo carbides rather than austenite cell. The change in corrosion processes and presence of WO 3 in the passivation film significantly contributed corrosion resistance. • W enhanced both corrosion resistance and mechanical properties of LDED-316. • Ferrite and W-Mo carbides decreased the corrosion priority of austenite cell. • W addition promoted the formation of thicker and compact passivation film. • WO 3 actively contributed to the formation of the passivation film. • Solidification mechanism and corrosion mechanisms were discussed in detail. [ABSTRACT FROM AUTHOR]

This work explores the relation between microstructural features and pitting corrosion resistance of additively manufactured 316 L stainless steel. Specimens fabricated using two different laser-based manufacturing processes (L-PBF and L-DED) were studied in as-built and heat-treated conditions following a comparative approach. Potentiodynamic polarization tests and corrosion morphology analysis served to evaluate their corrosion resistance and passive behavior. This work shows that, contrary to previous reports, the absence of MnS inclusions or presence of the microsegregation structure are not the main factors enhancing passivity of these materials. Instead, dislocation density was the only microstructural feature matching the trend in their passivity behavior. • Passivity follows relation (L-PBF>L-DED>Wrought) for heat treatment bellow 1000 °C. • Heat treatment above 1210 °C deteriorates corrosion resistance by enhancing IGC. • MnS inclusions and micro-segregation structure are not deciding factors in corrosion. • Dislocation density was the only microstructural feature matching trend in passivity. [ABSTRACT FROM AUTHOR]

The effect of tantalum addition on corrosion resistance in HAZ of duplex stainless steel was investigated by pitting corrosion test and material characterizations (SEM, TEM, APT). The Ta addition improved corrosion resistance of HAZ simulating welding at low heat input and rapid cooling rate since Ta segregated in the Cr nitrides and suppressed formation of Cr-depleted zone. The Ta addition also improved corrosion resistance in HAZ subjected to isothermal aging heat treatment assuming welding at high heat input and low cooling rate because Ta promotes the formation of χ phase and delays the formation of σ phase and Cr-depleted zone. • Ta addition improves corrosion resistance in HAZ of duplex stainless steel. • Ta suppresses Cr-depleted zone associated with Cr nitride formation. • Ta promotes χ phase formation and suppresses Cr-depleted zone associated with σ phase. [ABSTRACT FROM AUTHOR]

Corrosion behaviour of stainless steel was comparatively explored in 0.6 M KCl, KBr and their mixed solution. If Cl− and Br− ions simultaneously exist, Cl− ions were found to be less susceptible to metastable pitting corrosion and they can inhibit pit corrosion, which attributes Cl− ions have low adsorption coefficient or adsorption site to reduce pit growth from metastable to stable state. Pits will initiate at the locations where surface inclusions exist, which express morphological diversity during corrosion. This study expects to provide a new insight into the role of Cl− ion in corrosion of steel. • Cl− ions inhibit pit corrosion of stainless steel in Br− containing corrosive media. • Br− ions have a higher adsorption than Cl− ions during passivation. • Pits will initiate at the locations where surface inclusions exist. [ABSTRACT FROM AUTHOR]

In this study, the corrosion resistance mechanism of the Te and heat treatments on martensitic stainless steel (15–5PH steel) was investigated. Heat treatment affected the dislocation density of the Te-containing 15–5PH steel and reduced its corrosion tendency. Electrochemical dissolution of the MnS-Te inclusions induced pitting corrosion. Heat treatment significantly affects the potential difference between the Te-modified inclusions and the steel matrix, consequently influencing the emergence of pitting corrosion. Heat treatment improved the anti-corrosion properties of 15–5PH steel by transforming it from an active state to a passive state. The Mott-Schottky test results show that the passive film always exhibits n-type semiconductor characteristics and that the defect density of the passive film is reduced by the heat treatment. Heat treatment facilitated the enrichment of Cr, Te, and TeO 3 in the passivation film, resulting in its improved stability and corrosion resistance. The formation of an insoluble or slowly dissolved tellurite film through Te anodic oxidation, along with the self-healing properties of TeO 3 , improved the repassivation capability of the passivation film of the steel. • Heat treatment alters the corrosion resistance mechanism of Te-containing 15–5PH stainless steel. • Heat treatment affects the dislocation density and passivation film composition of Te-containing stainless steels. • Heat treatment improved the anti-corrosion properties of 15–5PH steel by transforming it from an active state to a passive state. [ABSTRACT FROM AUTHOR]

The effect of Cl− on the corrosion behavior of SiN stainless steel (SS) in simulating spent fuel reprocessing environment was systematically investigated. The results indicated that both cathodic and anodic behaviors of SiN SS were altered and multiple current peaks were observed as Cl− concentration increased. Meanwhile, there existed a critical Cl− concentration beyond which SiN SS transitioned from passive state to active dissolution state. Furthermore, a formulation for multiple current peaks was put forward based on mixed potential theory, and the corrosion mechanism in hot nitric acid with various Cl− concentrations was proposed involving the competitive adsorption of ions. • Cl− cannot induce pitting corrosion of SiN steel in 6 M hot nitric acid media. • Both cathodic and anodic behaviors of SiN steel in nitric acid are altered by Cl−. • Multiple current peaks are observed in nitric acid with 0.4 M Cl− and 0.45 M Cl−. • A critical concentration of Cl− with remarkable dissolution rate is determined. • Mechanism of Cl− on the corrosion of SiN steel in nitric acid is proposed. [ABSTRACT FROM AUTHOR]

Fretting crevice corrosion of total hip joints have been associated with joint replacement failure. However, researchers have not considered the interaction between fretting corrosion and crevice corrosion. In this study, an artificial crevice system that could perform fretting in the center of the crevice was designed, and fretting-initiated crevice corrosion (FICC) under different crevice widths, along with the effect of crevice corrosion on fretting corrosion, were studied. The results showed that FICC was more obvious under a smaller crevice, and pitting corrosion initiated at the shear band, resulting in crevice corrosion. Furthermore, corrosion pre-treatment significantly increased the fretting corrosion current. • Fretting corrosion was carried out inside the crevices with different widths. • Pits expand in shear bands due to fretting, resulting in accelerated corrosion. • Crevice corrosion pretreatment increases fretting corrosion current inside crevice. • Interaction of fretting and crevice corrosion is more marked at smaller crevice width. [ABSTRACT FROM AUTHOR]

The mechanical and electrochemical properties of AISI420 martensitic stainless steels (MSS) tempered at different temperatures (200, 400, and 600 ℃) are systematically investigated. The increased tempering temperature leads to the decreased strength, while the elongation remains relatively stable. Notably, the MSS tempered at 200 ℃ exhibits a superior strength-ductility synergy, featuring a strength of 1.65 GPa, and elongation of 10%. Moreover, increasing tempering temperature reduces the electrochemical properties and pitting corrosion resistance. In the tempered samples, pitting corrosion initiates near the inclusions and carbides, with the Cr-rich carbides and Cr-depleted regions serving as channels that promote the propagation of corrosion. • The AISI420 steel tempered at 200 ℃ showed the highest tensile strength and ductility. • Increasing tempering temperature reduces the pitting corrosion resistance. • Pitting preferentially initiates near the inclusions and Cr-rich carbides. • High density carbides at higher tempering temperature promote pitting propagation. [ABSTRACT FROM AUTHOR]

The distinct pitting behavior between the fusion zone of QN2109 laser welds and that of 317 L is investigated. The segregation of Mn is different in the two fusion zones due to differences in composition and cooling rate. Both welds contain residual δ-ferrite, with QN2109 displaying higher δ-ferrite content owing to its elevated Mn and N levels. The two welded joints exhibit diverse pitting initiation sites. QN2109 produces a secondary austenite prone to pitting during laser welding, whereas in the 317 L fusion zone, M 23 C 6 is dissolved, significantly reducing the number of pitting sites. • Secondary austenite was formed in QN2109 fusion zone, which was prone to pitting corrosion. • M 23 C 6 dissolves during laser welding, leading to a reduction of pitting initiation sites in 317L. • Mn exhibits different segregation in the two fusion zones due to elemental composition and heat input. • Both welds exhibit residual δ-ferrite, with QN2109 showing higher content due to its higher Mn and N content. [ABSTRACT FROM AUTHOR]

Laser powder bed fusion (LPBF) was performed on feedstock-modified 316L stainless steel powder with 1 and 2 vol% carbon nanotubes (CNT). The corrosion resistance was evaluated following cyclic potentiodynamic polarization tests conducted in 0.6 M NaCl at room temperature, 35 and 50 °C, and immersion tests in 6 % FeCl 3. The CNT addition has increased the pitting potential and decreased number of pits formed during immersion in FeCl 3 solution, which could be attributed to Mn-Si-O nano inclusions refinement and segregation of chromium around the inclusions. The observed corrosion behavior was correlated with the altered microstructure due to CNT addition. • Laser powder bed fusion of CNT-modified 316L stainless steel feedstock. • Enhanced pitting corrosion resistance due to the feedstock modification by CNT. • Pitting corrosion resistance evaluated at room temperature, 35 and 50 °C. • The altered microstructure-corrosion relationship due to CNT addition. [ABSTRACT FROM AUTHOR]

In this study, effect of extracellular polymeric substances (EPS) secreted by fungus Aspergillus terreus on the pitting corrosion of 316L stainless steels (SS) was deeply investigated by electrochemical measurements and surface analysis. Results demonstrated that adsorption of EPS can change surface wettability of 316L SS leading to a much more hydrophilic steel–water interface. EPS not only accelerates uniform corrosion but enhances pitting corrosion of 316L SS. EPS can promote the formation of metastable pitting corrosion and the subsequent growth of corrosion pits. The density of corrosion pits (>2 µm) reach (5.6 ± 0.5) × 103 pits/cm2 when EPS is 400 mg/L. • Effect of fungal EPS on the pitting corrosion behavior of 316L SS is investigated. • EPS can cause a much more hydrophilic steel–water interface. • EPS can cause a decrease of the passive film stability of 316L SS. • Anodic dissolution of Fe and cathodic reduction of oxygen are accelerated by EPS. • EPS promotes metastable pitting corrosion and the subsequent growth of corrosion pits. [ABSTRACT FROM AUTHOR]

Although manufacturers have optimized metallurgical routes to deliver super duplex stainless steels free from intermetallic phases, a segregated zone is generally formed close to mid-thickness for flat products. This zone may contain a small amount of sigma phase particles in the form of centerline intermetallic stringers. In this paper, their corrosion behaviour is investigated in sodium chloride solution, by coupling non-electrochemical and electrochemical techniques at the global and local scales. Corrosion mechanisms at centerline intermetallic stringers is then discussed and weak points in the sample are identified. • Discontinuous centerline intermetallic stringers do not impair the overall pitting corrosion resistance of the alloy. • The weakest sites of the alloy contain oxide particles. • Sites containing sigma precipitates are sensitive to pitting corrosion only at very high values of the applied potential. [ABSTRACT FROM AUTHOR]

The corrosion behavior of 316 stainless steel under the cooperation of plastic tensile stress and UV was investigated. The results showed that the pitting corrosion resistance of the film deteriorates under the combined effect of both factors. Among them, UV illumination could increase the Cr 2 O 3 ratio and reduce the electric field strength, thus improving the pitting corrosion resistance of the film. The plastic tensile stress not only increases the corrosion rate by increasing the defect density but also enhances the photo-induced electric field strength and photocurrent density by decreasing the band gap value and increasing the flat band potential. • The corrosion mechanism under the cooperative effect of stress and UV was studied. • UV illumination modifies the composition and electronic properties of the films. • UV illumination inhibits the dissolution of the passive film and the matrix. • Mechanism of plastic stress enhancing photoelectrochemical properties was proposed. [ABSTRACT FROM AUTHOR]

Inspired by the principle of copper-containing antibacterial stainless steel, a new type of Cu-Cr-bearing pipeline steel has been developed. Through a variety of surface characterization and electrochemical tests, the antibacterial property and microbiologically influenced corrosion resistance (MIC) of the novel type of steel were studied. Although the addition of Cu did not make this steel exhibit ideal antibacterial properties, all the results still showed that MIC resistance of the novel pipeline steel was better than that of X70 and Cr-bearing steels. The synergistic effect of Cr and Cu in the Cu-Cr-bearing pipeline steel contributed a beneficial effect to the improved MIC resistance. • The novel Cu-Cr bearing steel possesses better corrosion resistance than X70 steel in the presence of DvH. • The pit depth of X70 steel is twice more than that of Cu-Cr bearing steel in the presence of DvH. • The better pitting corrosion resistance of Cu-Cr bearing steel is the result of the synergistic effect of Cr and Cu. [ABSTRACT FROM AUTHOR]

The microstructure and corrosion resistance evolution of 316 L heat-affected zone were studied by simulated welding thermal technology. The different thermal simulation parameters affected the ferrite content and grain boundary characteristics. The ferrite content and grain boundary characteristics in thermal simulation samples were studied by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Combining the electrochemical test, it was observed that the Cr-depleted zone existed at the austenite/ferrite interface and the high angle grain boundary (HAGB) of the austenite interface usually became the nucleation point of pitting corrosion. • Retained ferrite can be found due to chromium aggregation during welding thermal cycle. • Cr-depleted zone and random high angle grain boundary are conducive to pitting nucleation. • Corrosion extends from ferrite/austenite phase boundary to austenite matrix. [ABSTRACT FROM AUTHOR]

The effect of the ferrite morphology on the pitting corrosion resistance of austenitic stainless steel weld metals solidified with primary ferrite was investigated. Most of the pitting corrosion occurred at the interface between ferrite and austenite—particularly at the vermicular ferrite/austenite interface; less pitting corrosion occurred at the lacy ferrite/austenite interface. This was because a Kurdjumov–Sachs orientation relationship was established between lacy ferrite and austenite. Consequently, Cr carbide was less likely to precipitate owing to the low interfacial energy, and the lacy ferrite/austenite interface was less likely to be an initiation site of pitting corrosion. • Pitting corrosion often occurs at interface between ferrite and austenite. • Initiation site of pitting corrosion is affected by ferrite morphology. • Cr23C6 is less likely to precipitate at lacy ferrite/austenite interface. • Lacy ferrite improve pitting corrosion resistance compared to vermicular ferrite. [ABSTRACT FROM AUTHOR]

The initiation site of pitting corrosion on type 304 stainless steel was quantitatively analysed using an automatic inclusion analyser and electron backscatter diffraction. In a sample anodically polarised at 0.43 V SSE , the fraction of stable pits initiated from inclusions was only 23 %. Pits initiated from sites other than inclusions probably initiated from grain boundaries, strain-induced martensite and scratches. In mixed inclusions of MnS and oxides, the probability of pit initiation increased with the S concentration. The Ti concentration had no effect on the probability of pit initiation, suggesting that whether Ti exists as TiO 2 or TiN is important. [Display omitted] • The initiation sites of pitting corrosion on type 304 stainless steel were quantitatively analysed. • Most pits initiated from grain boundaries, strain-induced martensite and scratches. • Among inclusions, MnS was the most likely to initiate pits. • In mixed inclusions of MnS and oxides, the probability of pit initiation increased at higher S concentrations. • The elements released from Ti-based inclusions may affect the tendency of pit initiation. [ABSTRACT FROM AUTHOR]

The α/γ phase selection mechanism and corrosion resistance of Fe-21%Cr-12%Ni-5%Mo alloy were investigated by both individual electromagnetic levitation (EML) and EML coupled with falling quench (EML+FQ) techniques. The decomposition of primary δ phase could be partially or completely suppressed in two containerless processing. Both selective and pitting corrosion behaviors were discovered in alloy, which were related to the crystalline orientations and solute distributions of constituent phases. The anti-corrosion property of EML+FQ processed alloy was significantly enhanced with higher corrosion potential of 0 V SCE , lower corrosion current density of 4.1 × 10−7 A/cm2 and lower corrosion rate decreasing over one order of magnitude. [Display omitted] • Multiple containerless processing method was proposed to improve the undercooling and cooling rate of alloy. • The decomposition of primary δ phase could be partially or completely suppressed in two containerless processing. • Corrosion behaviors of alloy were related to the crystalline orientations and solute distributions of constituent phases. • he in-situ observation of alloy corrosion process indicated different corrosion rate in two containerless processing. [ABSTRACT FROM AUTHOR]

• The erosion-corrosion of a SLM produced 316L SS was examined for the first time. • SLM-produced 316L SS has shown lower than expected erosion-corrosion resistance. • The unusual behaviour is due to the weak repassivation ability of SLM-produced 316L SS. The erosion-corrosion behaviour of a near fully dense 316L stainless steel (316L SS), with relative density higher than 99.5%, produced by selective laser melting (SLM) has been evaluated, for the first time, in a jet impingement system. Although the SLM-produced 316L SS possessed superior pitting corrosion resistance and higher hardness, unexpectedly, it has shown lower erosion-corrosion resistance than its conventionally produced commercial counterpart. This behaviour has been related to weaker repassivation ability of the SLM-produced 316L SS mainly due to the presence of the SLM process-induced pores within the specimen. [ABSTRACT FROM AUTHOR]

• The microstructure of Nickel-rich Custom 465 steel is significantly changed by various tempering temperatures. • Passive film stability first reduces and then increases with increasing tempering temperatures. • The Volta potential of the interface between nanoscale ɳ-Ni 3 Ti and the matrix is the lowest. • The Volta potential of reversed austenite is higher than that of martensite. The multiple effects of ɳ-Ni 3 Ti precipitates and reversed austenite on the passive film stability of nickel-rich Custom 465 steel were studied. The results showed that with an increase in tempering temperature, the η-Ni 3 Ti precipitates gradually coarsened. The Volta potential of the ɳ-Ni 3 Ti/matrix interface was approximately 30 mV lower than that of the precipitates, which decreased the passive film stability. The volume of reversed austenite gradually increased at higher tempering temperatures. The Volta potential of the reversed austenite was 14 mV higher than that of the martensite, which enhanced the passive film stability and slightly increased the pitting corrosion resistance. [ABSTRACT FROM AUTHOR]

• Anomalous evolution of corrosion behaviour was found in warm-rolled 304 steel. • Low angle and low-Σ CSL grain boundaries improve the pitting corrosion resistance. • Higher dislocation density weakens the pitting corrosion resistance. • The corrosion of warm-rolled steel is controlled by dislocation and grain boundary. The effect of warm-rolling (at 200 °C) on the corrosion behaviour of type 304 steel in the 3.5% NaCl solution was investigated by electrochemical measurements and microstructural characterization. The pitting corrosion resistance of the specimens decreased with increasing deformation, reached the bottom at 20% deformation, and then improved with further deformation. The increase in low angle and low-Σ coincidence site lattice (CSL) grain boundaries improves the corrosion resistance, while the higher dislocation density weakens the corrosion resistance. The corrosion behaviour of warm-rolled austenitic stainless steel is determined by the interplay of the dislocation and grain boundary effects. [ABSTRACT FROM AUTHOR]

• Lack of fusion pores controlled the breakdown potential (E b) to a first order, reducing it by up to 400 mV. • High heat input DED material observed a reduced E b attributed to chemical micro-segregation dictated by cooling rate. • The presence of δ overshadows the potentially beneficial effect to E b seen by nanoscale non-metallic inclusions. • Preferential dissolution of γ around the δ in DED material resulted in web-like pit covers and nest-like pit interiors. The impact of microstructure and processing defects of directed energy deposition (DED) 304L stainless steel on its corrosion behavior was investigated. Materials produced by DED with heat inputs of 0.45 and 0.03 kJ/mm were compared to wrought 304L. Lack of fusion pores in the DED material controlled breakdown potential (E b) to the first order, reducing it by up to 400 mV versus the base material in 0.6 M NaCl. The hierarchal control of these and other microstructure features, nanoscale oxides and δ -ferrite, and processing features on the E b of DED 304L is addressed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A new three-dimensional peridynamic model for pitting corrosion damage. • The 3D model simulates autonomous formation of lacy covers in stainless steel. • Simulation results are validated with 3D observations from literature. • Model reproduces observed lacy covers morphologies under various conditions. • Growth and merger of nearby pits and their lacy cover evolution are autonomous. Abstract A new three-dimensional peridynamic (PD) model is introduced for pitting corrosion damage. Based on simple mechanistic views of passivation, salt-layer presence, and passive-film rupture, the model simulates pitting corrosion damage in stainless steel in 3D, with autonomous formation of lacy covers. Computed lacy morphologies are strikingly similar to real pits. The model is validated against experiments. Merger of two 3D pits is studied and PD results compare well with experiments. The results imply that first-order mechanistic factors that determine corrosion rate, pit shape/size, and lacy cover morphology are those included in our model: diffusion, concentration-based damage, passivation, and salt-layer formation. [ABSTRACT FROM AUTHOR]

Highlights • An improved electrochemical method named thermal pulse technique was designed. • The CPT and repassivation temperature (T r) were measured in one thermal pulse. • The T r presented an inverted V-shape trend with the rise of cooling rate. • A model was proposed for the variation of T r in different thermal pulses. • The repassivation behavior was discussed according to the data of T r and E rp. Abstract An improved electrochemical method named thermal pulse technique was designed to measure the current flowing from a potentiostatically maintained UNS S31803 electrode in 1 M NaCl solution, while various thermal pulses were applied on the solutions. Both the critical pitting temperature (CPT) and the repassivation temperature (T r) were measured in one thermal pulse. The T r data presented an inverted V-shape trend as the cooling rate decreased. Both the CPT and T r values declined after multiple thermal pulses. The cyclic potentiodynamic polarization curves present a sharp transition of pitting and repassivation potential at the temperature ranged between the CPT and T r. [ABSTRACT FROM AUTHOR]

Highlights • First EN measurements with a commercial potentiostat validated with overlapping PSDs. • Localized corrosion of stainless steel in gel measurable with the EN technique. • Risk of crevice corrosion reduced with the portable-gel cell. • Stable pits formed potentiostatically in gel with chlorides at 200 mV vs. SCE. • Active-passive oscillations in all solutions in galvanostatic mode at 1.25 μA cm−2. Abstract The present paper presents pioneering results about the use of the electrochemical noise (EN) technique to study corrosion of metal surfaces of complex geometry in a gel electrolyte based on agar-glycerol, the composition of which was previously optimized for electrochemical measurements on stainless steel (SS) surfaces. EN results obtained with AISI 304 SS electrodes in both gelled and liquid electrolytes using three different modes (zero-resistance ammeter, potentiostatic, galvanostatic) of measurements have been compared and discussed. Tests carried out in gel allow the possibilities and limitations of using portable gel cells for monitoring corrosion of SS complex surfaces to be determined. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Detrimental effect was caused by the severe deformation areas with deformation bands. • Nitrogen was strongly enriched in the chromium oxide layer. • A self-healing reaction involving the nitrogen doping in passive film was concluded. Abstract Nickel-free high nitrogen stainless steels (HNS) with two nitrogen contents were studied to elucidate the role of nitrogen in eliminating detrimental effect of cold working on pitting corrosion resistance. It was found that the detrimental effect was caused by the severe deformation areas with deformation bands and completely eliminated in HNS with 0.92 wt.% nitrogen. Meanwhile, nitrogen was found to be significantly enriched as a form of short range ordered [CrN] in the chromium oxide layer of the passive film. Combined with chemical compositions and semiconducting properties analysis, a self-healing reaction involving the nitrogen doping in passive film was concluded. [ABSTRACT FROM AUTHOR]

The effects of electron beam welding and subsequent post-weld heat treatment at different temperatures on the microstructure evolution and pitting corrosion resistance of duplex stainless steel were investigated. The as-welded joint exhibited poor pitting corrosion resistance, and pitting preferentially occurred at the ferrite grain in the weld. Heat treatment promoted austenite formation, Cr 2 N dissolution, and eliminated dendritic segregation, consequently improving the corrosion resistance of the welded joint. The optimal solution temperature range was 1050–1110 °C. The austenite in the weld was prone to selective corrosion after heat treatment owing to its lower pitting resistance equivalent number. [ABSTRACT FROM AUTHOR]

The pitting behavior of 2205 duplex stainless steel after U-bending deformation was investigated under wet-dry cycling of droplets. At the tensile side, the average critical relative humidity for pitting (RH pit) was increased from 44.5% to 55.6%, the critical relative humidity (RH rep) for repassivation was correspondingly increased from 59.9% to 76.6%. The compressive strain increased the critical relative humidity to 52.9% (RH pit) and 73.3% (RH rep), respectively. Compared to the hemispherical pits without deformation, selective dissolution of the ferrite phase with irregular pits appeared on the tensile side. The decrease in pitting resistance and the formation of irregular pit morphology were discussed. • In-situ potential monitor and EIS analysis proved pitting under droplets on U-bent 2205 DSS. • Both tensile and compressive strain decreased the critical chloride content for pitting. • The pit probability increased on both the tensile and compressive strain sides. • The pit morphology on the tensile strain side was irregular with micro-cracks. • The pits on the compressive strain side present as shallow round-type morphology. [ABSTRACT FROM AUTHOR]

Studies of fungal corrosion for duplex stainless steels (DSS) in marine environments are poor. In this work, effects of fungus Aspergillus terreus on the structure of passive film and the subsequent corrosion behavior of 2205 DSS in artificial seawater were deeply investigated. Results indicated that A. terreus promoted local deterioration of 2205 DSS passive film by changing its structure and components compared to the abiotic control, and then significantly accelerated the corrosion of 2205 DSS especially pitting corrosion. The nucleation and growth of metastable pitting corrosion were accelerated by A. terreus. Furthermore, A. terreus could preferentially corrode the austenitic phase. [Display omitted] • Pitting corrosion behavior and mechanism of 2205 duplex stainless steel caused by fungus Aspergillus terreus are studied. • A. terreus can promote the deterioration of passive film leading to a severer pitting corrosion. • The nucleation and the growth of metastable pitting corrosion are accelerated by A. terreus. • A. terreus can preferentially corrode the austenitic phase. [ABSTRACT FROM AUTHOR]

This investigation proposes using Scanning Electrochemical Cell Microscopy (SECCM) as a high throughput tool to collect corrosion activity from randomly probed locations on 316 L SS. In the presence of chloride, potentiodynamic polarisation tests triggered the development of pitting corrosion. Data science methods were deployed to handle and explore 955 j Vs E curves. Normality tests and fitting with theoretical functions were used to understand the conditional log(j) distributions at different potentials. Unimodal and uniform distributions were assigned to the passive and pitting regions. Our "big-data" local strategy revealed a potential-dependent distribution of log(j) , with the randomness increasing with testing aggressiveness. All data generated or analysed during this study are included in this published article (and its supplementary information files) and are available in the Mendeley Data repository, [ https://data.mendeley.com/datasets/78rz8vw46x/2 ]. The code required to reproduce these findings is included in this published article (and its supplementary information files) and is available to download from GitHub: https://github.com/bcoelho-leonardo/Data-driven-analysis-of-the-local-current-distributions-of-316L-corrosion-in-NaCl-solution/blob/4efff485b115468840b25ea56ad81b31711c0f51/local%20current%20distributions%20of%20316L%20corrosion.ipynb. [Display omitted] • SECCM collected nearly 955 j Vs E curves of 316 L stainless steel in NaCl medium. • The unimodal log(j) distributions as a function of potential were rarely normal. • The more positive the potential, the higher the randomness (variances) of log(j). • Test aggressiveness is critical for the shift from unimodal to uniform distributions. • The uniform distribution was mainly assigned to E regions related to stable pitting. [ABSTRACT FROM AUTHOR]

The tribo-electrochemical behaviour of AISI 304 austenitic stainless steel in 0.5 M NaCl solution is investigated at an anodic potential of 70 mV(SCE) under controlled sliding and electrochemical conditions. It is found that at such an anodic potential where corrosion pits do not form without sliding, numerous micro-pits are found inside the sliding tracks under certain sliding conditions. There exists a critical combination of frequency, load and sliding duration for the development of the pits. The results are discussed considering the accumulation of mechanical damages induced by sliding and the competition between wear and pit growth during the process. [ABSTRACT FROM AUTHOR]

Tempering of 13 wt.% Cr martensitic stainless steel resulted in nano-sized M 3 C carbides at 300 °C, nano-sized Cr-rich M 23 C 6 carbides at 550 °C and sub-micron sized Cr-rich M 23 C 6 carbides at 700 °C. Austenitization resulted in lath martensite with undissolved M 23 C 6 carbides. Pitting resistance for tempered condition was lower than the austenitized condition with least resistance at 550 °C. The observation was attributed to the presence of a Fe-rich surface film and massive carbide precipitation with a Cr depletion zone of 7–9 nm at carbide interface for 550 °C tempered condition as opposed to a Cr-enriched passive film for the austenitized condition. [ABSTRACT FROM AUTHOR]

This work presents an innovative framework for the simulation of stable pit growth that accounts for the material microstructure in the computational model to investigate its effect on pit growth behavior. While many microstructural attributes can affect corrosion kinetics, the current work focuses on the effect of the crystallographic plane orientation at the corrosion front by utilizing variations in polarization behavior with orientation in a single phase material. The current modeling results show that crystallographic orientation significantly affects local pit growth rates (even with corrosion potential variations as little as 5–10% across orientations) and the resultant tortuous shapes are similar to pits observed in experimental studies. [ABSTRACT FROM AUTHOR]

The effect of cold deformation on the corrosion and passivation behaviour of UNS S31803 duplex stainless steel in saturated Ca(OH) 2 solution containing 3.5 wt.% NaCl was investigated. The results demonstrated that cold deformation changes the internal microstructure of two phases. Cold deformation was detrimental to the pitting corrosion resistance of duplex stainless steel. Metastable pitting events were enhanced by cold deformation. It also revealed that metastable pit initiation sites transfer from austenite phase to ferrite phase at cold deformation level higher than 70%. Moreover, compositions change and dehydration effect in the passive film were also related to cold deformation. [ABSTRACT FROM AUTHOR]

The development of metastable pit on sputtered nanocrystalline stainless steel was investigated in 3.5 wt.% NaCl solution. Its current transient is distinct from that of conventional coarse-grained stainless steel. The remnant thin membrane passive film over the pit mouth was found to act as a diffusion barrier, however, it do not undergo continuous rupture during the metastable growth, which restricted the diffusion rate of metal cations away from the pit and kept the current constant. The effect of remnant thin membrane passive film on the growth of metastable pit and its transition to stability has been discussed. [ABSTRACT FROM AUTHOR]

The effect of reversed austenite on the pitting behavior of super 13Cr martensitic stainless steel (S13Cr MSS) was investigated. The results revealed that reversed austenite was a FCC structure with Ni enrichment after tempering process, and there were no Ni-depleted regions adjacent to it. The reversed austenite content increased with increasing tempering temperature, and the pit depth decreased, as well as the dispersion degree of the Kelvin potential distribution. The reversed austenite reduced the risk of pitting corrosion through increasing the passive film compactness, and inhibiting Cl- penetration. Accordingly, the pitting corrosion resistance was enhanced as the tempering temperature increased. • Ni enriched reversed austenite content increased as the tempering temperature increased. • Reversed austenite formation restricted the movement of dislocations and reduced the dislocations density in the S13Cr MSS. • Reversed austenite reduced pitting corrosion through increasing the passive film compactness and inhibiting Cl- penetration. • High reversed austenite content led to the good pitting corrosion resistance for S13Cr MSS. [ABSTRACT FROM AUTHOR]

The effect of tellurium (Te) on the localised corrosion mechanism in 15–5PH stainless steel is studied in a simulated marine environment. The addition of Te changed the composition and size of the inclusions, which significantly affected the localised corrosion mechanism of the steel. Scanning Kelvin probe force microscopy and current-sensing atomic-force microscopy results show that the inclusions have good electrical conductivity and are always electrochemically dissolved. During the corrosion process, MnS acted as the anodic phase and was preferentially dissolved. The portion of Te in Te-containing complex inclusions increased the Volta potential of the inclusions and changed the localised corrosion mechanism. The appropriate addition of Te increased the pitting potential of 15–5PH stainless steel, thereby improving its localised corrosion resistance. However, superfluous addition of Te resulted in corrosion-resistance attenuation. This can be attributed to the continuous cathodic effect of the larger Te portion in the complex inclusion. The dissolution of Te oxides destabilised the passivation film. • The addition of Te to stainless steel changes the localised corrosion mechanism. • Galvanic coupling effects between the MnS-Te inclusion and steel matrix were revealed. • Appropriate Te addition enhanced the pitting potential and corrosion resistance of 15–5PH stainless steel. • Superfluous Te addition attenuated the corrosion resistance of 15–5PH stainless steel. [ABSTRACT FROM AUTHOR]

We use one-dimensional mass transport models to investigate the chloride concentration effect on the potential drop inside a pit cavity. Galvele's pitting model predicts a B value of 59 mV, independent of the complexation reactions and concentration-dependent diffusivity when ions can migrate freely. Higher B values (>59 mV) at 25 °C are commonly attributed to ion interactions in the pit solution, also explaining the material and electrolyte effect on the B value in Galvele's pit model. Our analysis suggests that practical pitting corrosion models require a comprehensive mass transport component that includes multi-species interactions. [ABSTRACT FROM AUTHOR]

The detrimental effect of cold working on pitting corrosion resistance was surprisingly found totally eliminated in high nitrogen stainless steels (HNS) with higher nitrogen content (0.92 wt.%) by electrochemical tests in chloride solution. Inclusions morphology and microstructure of cold-worked HNS were investigated. Then the passive film on HNS was analyzed by secondary ion mass spectroscopy (SIMS). For the first time nitrogen enrichment as a form of short range ordered [CrN] was observed in the chromium oxide layer of passive film on HNS. A possible reaction involving nitrogen enrichment is proposed to elucidate this exceptional behavior of corrosion resistance for HNS. [ABSTRACT FROM AUTHOR]

The effects of short-time heat treatment at different temperatures on the microstructure evolution and pitting corrosion behavior of UNS S32750 super duplex stainless steel welds were investigated. The results demonstrated that the ferrite phase in the as-welded heat-affected zone overwhelmed the austenite phase in content and was easily attacked by pitting corrosion. After short-time heat treatment, the excessive ferritization in the heat-affected zone was significantly alleviated. The highest pitting corrosion resistance of the welds was obtained at 1080 °C. [ABSTRACT FROM AUTHOR]

The influence of microstructural evolution on selective corrosion in duplex stainless steel flux-cored arc welding joint was investigated by the modified double loop electrochemical potentiokinetic reactivation in acidified chloride. Due to the lower pitting resistance equivalent number, the secondary austenite was preferentially attacked over the ferrite and primary austenite phases, and inclusions acted as nucleation sites for micro-pits in the weld metal. Localised corrosion was generated in the secondary austenite and Cr-depleted zone around the Cr 2 N and sigma phases in the heat-affected zone. The weld metal exhibited the smallest susceptibility to localised corrosion because of the least weak phases. [ABSTRACT FROM AUTHOR]

The pitting corrosion of sensitised stainless steel (SS) 304 during wet–dry cycling were investigated and compared with that of AR one. The average relative humidity for pitting corrosion during drying and repassivation during wetting correspondingly increased from 56% to 65% and from 67% to 79% by sensitisation. The decrease in pit potential and critical chloride concentration provides the degradation evidence of sensitised SS 304. The pitting probability and pit average size were promoted by sensitisation. The pit morphology changed from round to irregular shape. Such modification was possibly induced by preferential corrosion along grain boundaries where the pit initiated. [ABSTRACT FROM AUTHOR]

Stability of passive film of 2205 DSS in H 2 S-containing geothermal environments was investigated by immersion test, HTHP electrochemical measurement, surface analysis technique and thermodynamic calculation. The results showed that i p increased with p H2S rising from 0 to 33.1 bar at 150 °C. The presence of H 2 S prompted the FeS 2 and FeS formation in the corrosion product layer, leading to the degradation of the passive film. The adsorption of sulfur species caused the preferential dissolution of the phase boundary, and then the ferrite phase corroded and localized corrosion propagated under S-rich products. [Display omitted] • HTHP electrochemical tests showed enhanced Faradaic reactions due to the presence of H 2 S. • The adsorption of sulfur species caused the preferential dissolution of the phase boundary. • FeS 2 content increased with the rise of p H2S , with FeS as nucleation sites. • Localized corrosion propagates below S-rich products. [ABSTRACT FROM AUTHOR]

In this work, the effects of aging time on intergranular and pitting corrosion behavior of Cu-bearing 304L and 304L stainless steels were investigated by using the double loop electrochemical potentiokinetic reactivation (DL-EPR) and the potentiostatic polarization electrochemical methods. The results showed that the Cu-bearing 304L stainless steel possessed a higher intergranular corrosion tendency and a higher pitting corrosion rate for extended aging time. The TEM observation and 3D APT analysis confirmed that above behavior could mainly attribute to the precipitation of the Cu-rich phase in the Cu-bearing 304L stainless steel. [ABSTRACT FROM AUTHOR]

In this research, pitting corrosion of martensitic stainless steel in presence of halide anions was investigated by using polarization techniques. Results confirm that the aggressivity of halides increases in the following order: I − < Br − < Cl − . Although fluoride does not offer any pitting by itself, its presence together with chloride increases the occurrence frequency of metastable pits and pitting potential, simultaneously. While the pitting was more probable in NaCl solution, its metastable stability product was observed equal or even less than other solutions. [ABSTRACT FROM AUTHOR]

A single stable pit was initiated on the sputtered nanocrystalline stainless steel film. The pit shows two-step growth behavior. The pit growth rate and current density at each stage are constant. The interior morphology of the pit was observed. A series of outward-tilted concentric pit walls on the backside of the pit cover was discovered for the first time. These walls showed a constant spacing and presented an extremely regular configuration. Besides from the vestige of unreacted metal, the pit cover also contained the passive film which had originally covered the metal surface. [ABSTRACT FROM AUTHOR]

Time-of-flight secondary ion mass spectroscopy (ToF SIMS) analysis was performed on 316L stainless steel polarized potentiodynamically up to different potentials in NaCl solution. The surface film thickness increased with the ending potential of the potentiodynamic polarization, when estimated by the oxygen ion depth profiles. The chloride ion intensities at the film/metal interface were correlated with the ending potentials during the potentiodynamic polarization and cumulative anodic charge densities that govern the pit initiation. The results and analysis support the passivity breakdown mechanisms considering the role of chloride ions at the metal/film interface, rather than at the film/solution interface. [ABSTRACT FROM AUTHOR]