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• Novel NaNO 3 -based electrolyte with acetic acid additive for Mg-air batteries. • Anode efficiency boost and significant extension of cell lifespan beyond 360 h. • Reduction of Mg anode corrosion and hydrogen evolution reaction. • Crucial surface chemistry and morphology transformations revealed. Mg-air batteries have attracted tremendous attention as a potential next-generation power source for portable electronics and e-transportation due to their remarkable high theoretical volumetric energy density, environmental sustainability, and cost-effectiveness. However, the fast hydrogen evolution reaction (HER) in NaCl-based aqueous electrolytes impairs the performance of Mg-air batteries and leads to poor specific capacity, low energy density, and low utilization. Thus, the conventionally used NaCl solute was proposed to be replaced by NaNO 3 and acetic acid additive as a corrosion inhibitor, therefore an electrolyte engineering for long-life time Mg-air batteries is reported. The resulting Mg-air batteries based on this optimized electrolyte demonstrate an improved discharge voltage reaching ∼1.8 V for initial 5 h at a current density of 0.5 mA/cm2 and significantly prolonged cells' operational lifetime to over 360 h, in contrast to only ∼17 h observed in NaCl electrolyte. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry were employed to analyse the composition of surface film and scanning electron microscopy combined with transmission electron microscopy to clarify the morphology changes of the surface layer as a function of acetic acid addition. The thorough studies of chemical composition and morphology of corrosion products have allowed us to elucidate the working mechanism of Mg anode in this optimized electrolyte for Mg-air batteries. [ABSTRACT FROM AUTHOR]

X‐ray photoelectron spectroscopy analysis was applied to investigate the thermal stability under ultra‐high vacuum environment of the surface oxide film formed by electrochemical passivation of a newly designed Cr15Fe10Co5Ni60Mo10 (at.%) multi‐principal element alloy and providing the alloy superior localized corrosion resistance compared to conventional stainless steels and alloys. A spectral decomposition methodology involving the subtraction of Auger peaks overlapping the Fe 2p and Co 2p core level regions was applied for quantification of the oxide film composition and thickness. The results show that, at 100°C, the passive oxide film is mainly dehydrated and dehydroxylated. Obvious loss of Ni hydroxide and conversion of Mo (VI) to Mo (IV) species are observed at 200°C, with further reduction of Mo species to Mo (III) observed at 300°C. In this temperature range, the total cation quantity in the oxide film remains stable despite the compositional alteration. At 400°C, Cr (III) oxide forms at the expense of Fe and Mo oxides, resulting in an oxide film essentially consisting of chromium oxide. At 500°C, Cr (III) oxide is eliminated, making the passive film unstable at this temperature. Possible Cr oxide removal mechanisms are discussed. [ABSTRACT FROM AUTHOR]

The formation and evolution of the solid electrolyte interphase (SEI) layer as a function of electrolyte and electrolyte additives has been extensively studied on simple and model pure Si thin film or Si nanowire electrodes inversely to complex composite Si-based electrodes with binders and/or conductive carbon. It has been recently demonstrated that a binder-free Si@C-network electrode had superior electrochemical properties to the Si electrode with a xanthan gum binder (Si-XG-AB), which can be principally related to a reductive decomposition of electrolytes and formation of an SEI layer. Thus, here, the Si@C-network and Si-XG-AB electrodes have been used to elucidate the mechanism of SEI formation and evolution on Si-based electrodes with and without binder induced by lithiation and delithiation applying surface analytical techniques. The X-ray photoelectron spectroscopy and time-of-flight ion mass spectrometry results demonstrate that the SEI layer formed on the surface of the Si-XG-AB electrode during the discharge partially decomposes during the subsequent charging process, which results in a less stable SEI layer. Contrarily, on the surface of the Si@C-network electrode, the SEI shows less significant decomposition during the cycle, demonstrating its stability. For the Si@C-network electrode, initially, the inorganic and organic species are formed on the surface of the carbon shell and the silicon surface, respectively. These two parts of species in the SEI layer gradually grow and then fuse when the electrode is fully discharged. The behavior of the SEI layer on both electrodes corroborates with the electrochemical results. [ABSTRACT FROM AUTHOR]

Trivalent Chromium Process (TCP) was developed as a promising conversion process aiming at enhancement of corrosion properties and adhesion of aluminium alloys. The alkaline etching and acid pickling are usually applied as surface pretreatments on aluminium alloys before TCP deposition in order to optimize their properties. In this work, the surface modifications of an Al-Cu- Li alloy (AA2050-T8) at different stages of pretreatment (alkaline degreasing and acid pickling) and subsequent TCP are investigated by X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry and scanning electron microscopy. The pretreatments leading to significant enrichments in Cu and less marked in Ag, show also a strong influence on the subsequent formation of TCP in comparison to the non-pretreated, polished AA2050-T8 alloy. A slight decrease in Li content is observed in the oxide layer after pretreatment and no Li is present in the outer TCP layer. A thicker TCP conversion coating (outer oxide) with less cracks is formed on the pretreated alloy surface than on the polished one. Moreover, a Cu enrichment is evidenced in the TCP layer of the pretreated sample, which results in enhanced cathodic activity of pretreated sample with reference to polished sample as demonstrated by linear sweep voltammetry. [ABSTRACT FROM AUTHOR]

X-ray Photoelectron Spectroscopy and Time-of-Flight Secondary Ion Mass Spectrometry were combined to characterize the surface oxides (native oxides and passive films) formed on Ni-based alloys containing chromium and molybdenum. Two alloys were studied, Ni-20Cr and Ni-20Cr-10Mo (in wt.%). For Ni-20Cr, both native oxide and passive films formed in acidic medium present a duplex structure comprising a Ni and Cr outer hydroxide layer and a Cr inner oxide layer. The Ni-20Cr-10Mo alloy presents a similar bilayer structure, but with Mo oxide located at the outer layer/inner layer interface. Cr enrichment is observed after passivation for both alloys. The corrosion resistance in acidic solution containing chlorides is enhanced by Mo, and by electrochemical pre-passivation in Cl free solution. [ABSTRACT FROM AUTHOR]

A combination of electrochemical measurements, H2 volume measurements and surface analysis using Time-of-Flight SecondaryIon Mass Spectrometry (ToF-SIMS) and X-ray Photoelectron Spectroscopy (XPS) was used to investigate the role of the metallic Fe impurities (60 ppm) in high purity (99.9 wt%) magnesium and the effect of sulfur on the hydrogen evolution. The Mg corrosion was studied in NaCl solutions containing dissolved hydrogen sulfide. At OCP and under anodic polarization the hydrogen evolution reaction and the growth of dark corroded areas were significantly inhibited in the presence of H2Saq. ToF-SIMS and XPS analyses showed the presence of sulfur adsorbed on Mg and on Fe segregated at grain boundaries. The observed inhibition of hydrogen evolution at OCP and above is assigned to a poisoning effect by adsorbed S of the H adsorption sites on segregated iron which, in the absence of sulfur, provides catalytic sites for excess HER. The equilibrium Pourbaix diagram for the Mg-Fe-S system including the adsorbed species predicts that S is adsorbed on Mg and Fe in the E-pH conditions of this work, which confirms therole assigned to adsorbed sulfur in the inhibition of excess hydrogen evolution at OCP and under anodic polarization in the presence of H2Saq. [ABSTRACT FROM AUTHOR]

The aim of this work was to investigate the bacteria-surface interactions occurring during the first hour of adhesion of marine Pseudoalteromonas NCIMB 2021 at the surface of 2304 lean duplex stainless steel in artificial seawater. A complete characterization of the biofilm and the passive film was performed coupling epifluorescence microscopy, scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and time of flight secondary ion mass spectrometry (ToF-SIMS). The coupling of XPS and ToF-SIMS analyses revealed that (1) protein and polysaccharide contents in the biofilm are similar in the presence or absence of nutrients, (2) the biofilm is mainly composed of proteins and the protein content is similar to the one of Tightly Bound EPS, (3) increased bacterial activity due to nutrients leads to chromium enrichment in the passive film in close vicinity to the bacteria. [ABSTRACT FROM AUTHOR]

Time of Flight Secondary Ion Mass Spectroscopy, X-Ray Photoelectron Spectroscopy, in situ Photo-Current Spectroscopy and electrochemical analysis were combined to characterize the physicochemical alterations induced by electrochemical passivation of the surface oxide film providing corrosion resistance to 316L stainless steel. The as-prepared surface is covered by a ~2 nm thick, mixed (Cr(III)-Fe(III)) and bi-layered hydroxylated oxide. The inner layer is highly enriched in Cr(III) and the outer layer less so. Molybdenum is concentrated, mostly as Mo(VI), in the outer layer. Nickel is only present at trace level. These inner and outer layers have bandgap values of 3.0 and 2.6-2.7 eV, respectively, and the oxide film would behave as an insulator. Electrochemical passivation in sulfuric acid solution causes the preferential dissolution of Fe(III) resulting in the thickness decrease of the outer layer and its increased enrichment in Cr(III) and Mo(IV-VI). The further Cr(III) enrichment of the inner layer causes loss of photoactivity and improved corrosion protection with the anodic shift of the corrosion potential and the increase of the polarization resistance by a factor of ~4. Aging in the passive state promotes the Cr enrichment in the inner barrier layer of the passive film. [ABSTRACT FROM AUTHOR]

To elucidate the role of noble metal impurities on corrosion of Mg, 3D time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging in combination with X-ray photoelectron spectroscopy and optical microscopy measurements were carried out on Mg samples (99.9%) before and after Mg polarization at EOCP+0.5 V in 0.1 M NaCl. A significant segregation of Fe (and of Mn and Al) metallic impurities at grain boundaries (GBs) was observed on the Mg surface by 3D ToF-SIMS. A 3-step mechanism of Mg corrosion was proposed, including a catalytic effect of Fe segregated at the GBs on the hydrogen evolution reaction (HER). In the 1st stage, the initiation of Mg corrosion is accompanied by the HER occurring over Fe impurities segregated at GBs leading to formation of small circular defects and propagation with occurrence of dark filiform-like pattern corrosion enriched in Cl-. In the 2nd stage, segregated Fe metallic particles are released by Mg matrix undermining, and are dissolved into Fe2+ ions and in the 3rd stage a redeposition of Fe in the clear areas of Mg surfaces, corresponding to areas with low concentration of Cl-, takes place. [ABSTRACT FROM AUTHOR]

• XPS and ToF-SIMS techniques were applied to understand biofilm-surface interaction. • The effect of Escherichia coli on the passive film composition has been explored. • Escherichia coli adhesion leads to a Cr enrichment of the passive film. • A mechanism involving bacterial metabolism explains passive film modifications. Modifications of the passive film on stainless steel (316 L) after Escherichia coli adhesion in the early stage of biofilm formation were investigated by XPS (X-ray Photoelectron Spectroscopy) and ToF-SIMS (Time-of-Flight Secondary Ions Mass Spectrometry). This work evidences an enrichment in Cr(III) in the presence of bacteria, which is known to improve corrosion resistance. The iron depletion is assigned to synthesis by bacteria of organic molecules (siderophore) that specifically chelate Fe3+ ions from the passive layer, followed by the reduction of Fe3+ into Fe2+ ions by the bacterium and finally release of these reduced species into the aqueous solution. [ABSTRACT FROM AUTHOR]

Electrochemical polarization measurements were combined with surface analysis by Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS), X-Ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM) to study the alterations of the passive film on 316 L austenitic stainless steel induced by the presence of chlorides in sulfuric acid electrolyte. The work was performed at a stage of initiation of localized corrosion preceding metastable pitting at the micrometer scale as verified by current transient analysis and AFM. The results show that Cl− ions enter the bilayer structure of the surface oxide already formed in the native oxide-covered initial surface state at concentrations below the detection limit of XPS (<0.5 at%), mostly in the hydroxide outer layer where Fe(III) and Mo(IV,VI) species are concentrated but barely in the oxide inner layer enriched in Cr(III). Their main effect is to produce a less resistive passive state by poisoning dehydroxylation and further Cr(III) and Mo(IV,VI) enrichments obtained in the absence of chlorides. This detrimental effect can be suppressed by pre-passivation in a Cl−-free electrolyte, which blocks the entry of chlorides in the passive film, including in the outer exchange layer, and enables the beneficial aging-induced variations of the composition to take place despite the presence of chlorides in the environment. [ABSTRACT FROM AUTHOR]

• The air-formed oxide on Hastelloy BC-1 contained Cr- and Mo- rich regions in the inner and outer oxide, respectively. • Empirical evidence shows O atom incorporation at the outer interfaces of both the Cr- and Mo-rich regions of the oxide. • Heating the air-formed oxide to 300 °C did not increase its thickness, but, further heating to 500 °C led to the thickening. • In all cases, temperature increases induced structural modification to the oxides which then reverted during oxidation. This paper presents insight into the structure and transport mechanisms involved in the surface oxidation of Hastelloy BC-1, gained by means of in situ time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The native, air-formed oxide, comprising Cr-rich (inner) and Mo-rich (outer) layers, was found to be on the order of 1–2 nm thick. Oxide thickness did not change when the temperature was increased to 300 °C in oxygen atmosphere but increased to ˜10 nm after exposure at 500 °C. The mechanisms of oxide growth/maintenance as well as observations on the effect of elevated temperatures on oxide structure are discussed. [ABSTRACT FROM AUTHOR]

• Formation of bi-layered films with physisorbed outer and chemisorbed inner layers. • 2-MBI bonding by N to metallic and oxidized Cu, S also involved on metallic Cu. • Formation of Cu(I)−2-MBI complex promoted by cathodic conversion of native Cu oxide. • Increased complex formation owing to Cu(I) ions generated by anodic oxidation. • Cu dissolution inhibited depending on pre-treatment used for interface formation. The interfacial bonding and the layered structure of 2-mercaptobenzimidazole (2-MBI) organic films adsorbed on electrochemically controlled copper surfaces and their corrosion inhibition effects in acidic chloride aqueous solution were investigated using an integrated approach of electrochemical methods and advanced surface analyses by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. It is shown that organic films formed on the copper surfaces are bi-layered with a chemisorbed inner layer and a physisorbed outer layer. In the chemisorbed inner layer, 2-MBI is bonded primarily by its nitrogen atoms with metallic and oxidized copper surfaces. Sulphur atoms are also involved in the bonding mechanism when metallic copper is directly accessible to the 2-MBI molecules. The initial presence of native copper oxides at the interface promotes the formation of Cu(I)-2-MBI metal-organic complexes in the chemisorbed inner layer using cathodic reduction to dissociate the oxide. Metal-organic complexes also form upon anodic polarisation due to Cu(I) ions generated by oxidation of the copper metal. 2-MBI effectively inhibits copper anodic dissolution in varying degrees, between 84% and 93%, depending on the pre-treatment used for the formation of the organic bi-layers. An enhanced protection of the substrate is obtained by adsorbing the 2-MBI inhibitor on an initially oxide-free surface, which is achieved by cathodic pre-treatment in absence of the inhibitor followed by 1 hour exposure to the inhibitor. [ABSTRACT FROM AUTHOR]

The role of the SiC substrate surface on the resistance to the local initiation of tarnishing of thin-layered silver stacks for demanding space mirror applications was studied by combined surface and interface analysis on model stack samples deposited by cathodic magnetron sputtering and submitted to accelerated aging in gaseous H 2 S. It is shown that suppressing the surface pores resulting from the bulk SiC material production process by surface pretreatment eliminates the high aspect ratio surface sites that are imperfectly protected by the SiO 2 overcoat after the deposition of silver. The formation of channels connecting the silver layer to its environment through the failing protection layer at the surface pores and locally enabling H 2 S entry and Ag 2 S growth as columns until emergence at the stack surface is suppressed, which markedly delays tarnishing initiation and thereby preserves the optical performance. The results revealed that residual tarnishing initiation proceeds by a mechanism essentially identical in nature but involving different pathways short circuiting the protection layer and enabling H 2 S ingress until the silver layer. These permeation pathways are suggested to be of microstructural origin and could correspond to the incompletely coalesced intergranular boundaries of the SiO 2 layer. [ABSTRACT FROM AUTHOR]

The effects of surface pretreatments (degreasing and pickling) on the characteristics of the Trivalent Chromium Process (TCP) coating on pure aluminum and on AA2024-T351 aluminum alloy were investigated here by means of surface sensitive techniques: X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The XPS and ToF-SIMS results evidence that the TCP coating homogeneity is strongly dependent on the pretreatment process used. The TCP coverage factor, calculated from XPS results, is significantly lower, on both pure aluminum and AA2024-T351 alloy surface, when a pickling step is applied. One of the main effects of pickling pretreatment is strong metallic copper enrichment at the surface of the 2024 alloy, associated with chemical dissolution of Al-Cu intermetallic particles. However, it is evidenced here, that the copper enrichment is not detrimental for the quality of the TCP coating. The coating failure, observed when the pickling step is applied, can be assigned to a faster kinetics of the coating growth leading to formation of thicker conversion coating more susceptible to cracking or to the localized presence of aluminum fluoride species leading to the appearance of coating defects or detachment. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ions mass spectrometry (ToF-SIMS) analyses were performed to characterize the interaction of Cu with mercaptobenzothiazole (MBT) in aqueous solution for 1 h and 24 h in absence and presence of NaCl. The fingerprints of the molecules are identified with XPS (S, N and C signals). The analysis of the Cu 2p core level and Auger Cu peaks allow us to show that the Cu metal is covered by a Cu 2 O oxide layer whose thickness increases with exposure time in the absence of MBT. It is found that MBT forms multilayers on Cu oxide and inhibits the oxide layer growth. The XPS data are consistent with MBT adsorbed on oxide in multilayers, with a small fraction adsorbed on metallic Cu. These interactions are then further characterized using ToF-SIMS. The results suggest adsorption of the MBT molecules in a strongly bonded layer through both S atoms of the organic molecule oriented towards the surface, covered by a weakly bonded multilayer. Quantitative treatments of XPS intensities allows us to evaluate a layer thickness of 23 Å and 32 Å after 1 h and 24 h, respectively. Co-adsorbed water is also identified. The presence of water in the organic layer (ratio H 2 O/MBT = 0.28) may explain the orientation of the molecules with S directed towards the surface and N interacting through H bonds with water molecules, as suggested by complementary DFT calculations. The adsorption of MBT is similar in presence of NaCl and in pure water, and also inhibits the oxide growth. In addition, MBT adsorption inhibits the adsorption of Cl on the Cu surface. Inductively Coupled Plasma Optical Emission Spectrophotometry (ICP OES) experiments demonstrate that MBT adsorption inhibits Cu dissolution, even after 20 days immersion in NaCl. Thus, we demonstrated that MBT, by adsorbing and forming a full monolayer at the Cu surface, inhibits further oxide growth, Cl adsorption and copper dissolution in NaCl. [Display omitted] • MBT adsorbs on Cu immersed in water and forms multilayers with thicknesses of 2.3–3.2 nm. • Adsorbed MBT inhibits the copper oxide growth, Cl adsorption and copper dissolution in NaCl. • The first MBT layer close to the substrate is bonded to copper via the two S atoms oriented towards the surface. • Water is present in the organic film in a ratio H 2 O/MBT = 0.28. • Water in the organic film has a determinant role in molecule orientation, as shown by DFT calculations. • A fraction of MBT is adsorbed on metallic copper, healing some depassivated areas. [ABSTRACT FROM AUTHOR]

• 5-sulfosalicylate as an inhibitor in 0.6 M NaCl electrolyte is used for Mg-air battery. • Upon the inhibitor application the improved discharge voltage and battery lifetime are observed. • Almost a four-fold reduction of the hydrogen evolution and a reduced Mg corrosion are noticed. • A modified structure and composition of the surface layer is observed. This work aims at employing sodium 5-sulfosalicylate (5-S-Sal) corrosion inhibitor into aqueous NaCl electrolyte to improve the discharge performance of Mg-air battery and decrease the side reactions of Mg anode. The corrosion tests at open circuit potential show a four-fold decrease of hydrogen evolution when 5-S-Sal inhibitor is added. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry analyses show that due to the presence of 5-S-Sal inhibitor, a corrosion resistant layer has a lower quantity of Mg(OH) 2 (by ∼15%) than that formed in NaCl electrolyte. The surface enrichment in S-like species originating from inhibitor molecule could have an important effect on a decreased corrosion and slow down the H 2 evolution. Within a range of concentrations of 5-S-Sal in NaCl electrolyte (0.05 to 0.15 M), the best discharge performances are achieved with 0.1 M inhibitor. The discharge voltage of full Mg-air battery improves from ∼1.58 to ∼1.82 V at 0.5 mA/cm2 and the discharge lifetime is extended from around 12.5 to around 80 h. Scanning electron microscopy and 3D topography laser microscopy indicate that during the discharge tests much smaller surface degradation occurs and a more uniform surface layer is formed in the presence of inhibitor in the NaCl-based electrolyte. [ABSTRACT FROM AUTHOR]

Abstract: Sn–Co alloy films were prepared by electroplating on copper and used as anode material of lithium ion battery. Cyclic voltammetry and galvanostatic discharge/charge measurements were combined with surface analysis by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results show the buildup of a solid electrolyte interphase (SEI) layer formed by reductive decomposition of electrolyte during the first Li–Sn alloying cycle. The layer is constituted of a mixture of Li2CO3, ROCO2Li, lithium oxalates, and/or ROLi, and its chemical composition is modified during the electrochemical multi-cycling process with increase of the Li2CO3 content. Multi-cycling also fractures the SEI layer. ToF-SIMS results revealed an incomplete initial alloying process of lithium ion with Sn, limited by mass transport through a Co layer and dividing the Sn–Co layer alloy into a fully lithiated outer part and an essentially non-lithiated inner layer during the first discharge. The volume expansion/shrink associated with the alloying/dealloying reaction irreversibly cracks and splits up the Sn–Co alloy into particles with interstitials voids filled by the SEI layer. Multi-cycling amplifies this division of the Sn–Co layer without material loss and stabilizes discharge/charge capacity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chemical speciation of buried interface on rough substrates. • Sputtering by GD-OES and ToF-SIMS to access interfaces for XPS analysis. • GD-OES homogenous sputtering of thin conversion coating on rough substrate. • Application of Auger nanoprobe for characterization of local coating distribution. • Homogenous in-depth distribution of Cr in conversion coating. In order to describe the chemical composition and the distribution of a thin trivalent chromium conversion coating on rough electrodeposited Zn-based alloy substrate, a methodology combining surface analytical and sputtering techniques was used. A sputtering by argon in glow discharge optical emission spectrometry (GD-OES) and by oxygen using time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to monitor the in-depth chemical composition evolution of the conversion coating and define the metal-conversion coating interface. Surface topography measurements were performed by high resolution 3D optical microscope. The chemical characterization of the conversion coating on the top surface and near the rough metal-oxide interface inside the craters was performed by X-ray photoelectron spectroscopy. The local depth and composition of the conversion layer inside and outside the craters were performed by Auger electron spectroscopy nanoprobe equipped with coaxial detector to prevent from shadowing effect during measurement. The results indicated inhomogeneous sputtering inside the ToF-SIMS craters, which was attributed to the shadowing effect, caused by the roughness of the substrate and the 45° incidence angle ion gun. GD-OES sputtering appeared homogeneous in different areas inside the crater despite the roughness of the substrate, which was attributed to the perpendicular incidence angle of the sputtering. [ABSTRACT FROM AUTHOR]

[Display omitted] • Interfacial passivation mechanisms studied on Cr- and Mo-containing alloy surfaces. • D 2 O labelling applied to study the growth of nanometer-thick passive oxide film. • D-labelled species mostly detected in outer hydroxide layer of passive film. • Minor inward hydroxyl diffusion from electrolyte during anodic passivation. • Key role of hydroxyls initially in native oxide in forming Cr hydroxide. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) combined with deuterium labelling (D 2 O), and X-ray photoelectron spectroscopy (XPS) were applied to investigate the interfacial transport mechanisms of hydroxyls between aqueous electrolyte and outer part of the protective oxide film during passivation of Cr 15 Fe 10 Co 5 Ni 60 Mo 10 multi-principal element alloy surfaces. A ToF-SIMS signal treatment methodology was developed to retrieve the in-depth distribution of deuterated hydroxides in the nanometer-thick surface oxide film. After immersion at free potential or anodic passivation in acidified D 2 O, the initial bilayer structure is retained. The use of heavy water electrolyte has no effect on the composition alterations induced by passivation. Deuterated species were detected mostly in the outer layer of the surface oxide film. Pure inward hydroxyl diffusion from electrolyte/oxide to oxide/metal interface is excluded from being primarily responsible for oxide film growth induced by anodic passivation. The hydroxyls from the dissolving hydroxide species are retained in the oxide film and participate in forming Cr hydroxide, thus reducing the hydroxyl surface uptake from the electrolyte. This work provides deeper insight into the mechanisms of oxide growth and corrosion protection induced by anodic passivation. [ABSTRACT FROM AUTHOR]

Low corrosion protection performances of Trivalent Chromium Process (TCP) coatings with reference to Chromium Conversion Coatings (CCC) deposited on aluminium alloys can be overcome by application of post-treatment processes. This work shows the effect of post-treatment bath (containing hydrogen peroxide and lanthanum salt) on the chemical composition, structure and the corrosion performances of TCP coating deposited on AA 2024-T3 aluminium alloy. Different times of post-treatment bath were applied on the TCP coating and the samples were analyzed by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), X-ray Photoelectron Spectroscopy (XPS) and Glow Discharge-Optical Emission Spectrometry (GD-OES). The ToF-SIMS and GD-OES depth profiles show that the post-treatment time has no influence on the thickness of the TCP coating and on its bi-layered structure. It is composed of an outer layer, rich in zirconium and chromium oxides and an inner layer rich in aluminium oxides and oxy-fluorides. 3D ToF-SIMS images reveal an enrichment of Cr and Zr-like species over the surface of intermetallic particles with reference to alloy matrix, whereas a homogenous distribution of La is observed. The analysis of in-depth distribution shows that La is present principally in the outer part of the TCP coating. The La concentration increases with increasing post-treatment time. The effect of post-treatment time on protection was evaluated by Electrochemical Impedance Spectroscopy (EIS) and Linear Sweep Voltammetry (LSV) in a 0.001 M NaCl + 0.1 M Na 2 SO 4 electrolyte. The increased post-treatment time enhances the cathodic inhibition against oxygen reduction. The post-treatment provides improved coating homogeneity and sealing properties. • No thickness and structure modification of TCP coating induced by post-treatment • Significant inhibition of the cathodic oxygen reduction induced by post-treatment • Increase of La and decrease of Cr in TCP with higher post-treatment time • Homogenous surface distribution of La responsible for sealing coating defects [ABSTRACT FROM AUTHOR]

• Investigation of native and passive surface films formed on Ni-20 at.% Cr alloy surfaces. • Surface analysis by in situ electrochemical measurements combined with advanced ex situ surface analysis. • Mechanistic understanding of the effects of high-temperature hydrogen annealing pretreatment. • Enhanced corrosion resistance of electrochemically passivated surface by high-temperature hydrogen annealing pretreatment. • Increase in Cr enrichment of initially weakly protected sites of the inner barrier layer. The effect of high-temperature annealing under hydrogen gas (H 2) surface preparation on a binary polycrystalline Ni-20 at.% Cr alloy was investigated in comparison with conventional mechanical grinding surface preparation. Duplex surface films with inner Cr(III) oxide and outer Ni(II) and Cr(III) hydroxide layers natively formed before and after H 2 annealing were characterized by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy. A thinner and less homogeneous inner barrier layer formed after H 2 annealing caused an oxidation peak at the active/passive transition in the linear sweep voltammetry measurement in a 0.5 M H 2 SO 4 solution. Despite this high oxidation peak, passivation of the H 2 annealed surface resulted in the formation of a more corrosion resistant inner layer than on the mechanically ground surface, as demonstrated by electrochemical impedance spectroscopy. The corrosion resistant passive film formation of the H 2 annealed surface is attributed to the increased Cr enrichment of the inner layer caused by the selective Ni dissolution providing corrosion resistance to the initially weakly protected sites of the natively formed surface film. [ABSTRACT FROM AUTHOR]

Room temperature ionic liquids (RTILs) attract much attention as a new type of environmentally benign electrolytes for Li-ion batteries due to their numerous interesting physicochemical properties. Here, in this paper, Li intercalation/deintercalation in presence of the N -butyl- N -methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (PYR 14 TFSI) and N -methyl- N -propylpyrrolidinium bis(fluorosulfonyl)imide (PYR 13 FSI) containing 0.3 M LiTFSI, was evaluated in a thin 100 nm layer of V 2 O 5 deposited on Al substrate by atomic layer deposition. Potentiodynamic tests performed in LiTFSI/Pyr 14 TFSI show a quasi-reversible Li intercalation during 10 cycles (between 2.4 and 5 V) with an average coulombic efficiency of 99%. The capacity, calculated from the 1st cycle, is found to be 182 mAh g −1 , about 19% (±2%) higher than the theoretical capacity reported for V 2 O 5 (147 mAh g −1 ). X-ray photoelectron spectroscopy analysis confirms that the intercalation of more than 1 mol of Li + per V 2 O 5 is achieved as also the possible presence of a solid permeable interface (SPI) layer on the V 2 O 5 surface. Likewise, the Li + in-depth distribution on the V 2 O 5 layer after intercalation in RTILs measured by time-of-flight secondary ion mass spectrometry ion depth profiles, show small irreversible electrode modifications with the presence of lithium through the entire V 2 O 5 layer with significant lithium trapping at the V 2 O 5 layer/Al substrate interface. [ABSTRACT FROM AUTHOR]

• Corrosion inhibition and interfacial bonding of 2-MBT studied on copper. • Electrochemistry combined with advanced surface analysis by XPS and ToF-SIMS. • Inhibition enhanced by cathodic reduction of interface before 2-MBT adsorption. • 2-MBT bonded to metallic copper and copper oxide islands via the S atoms. • Exo- and endocyclic S atoms released by dissociation and bonded to metallic Cu. Electrochemistry along with advanced surface analyzes (X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry) were implemented to investigate copper corrosion inhibition by 2-mercaptobenzothiazole (2-MBT) in hydrochloric aqueous solution and the effects of electrochemical control on the formation of the inhibiting interface. It is shown that reducing the native surface oxide by cathodic reduction prior to exposure to the inhibitor drastically decreases the rate of anodic dissolution. Additionally, increasing the exposure time of the metal surface to the inhibitor results in even better protection against dissolution. 2-MBT adsorbs as multilayers and bonds to both metallic copper and residual copper oxide islands via its sulphur atoms. Partial dissociation of the molecule, releasing the exocyclic sulphur, which then bonds to metallic Cu, is observed. Further dissociation of the molecule, releasing the endocyclic sulphur, is induced by anodic polarization, forming defects in the organic layer and thus compromising the barrier properties of the organic layer. [ABSTRACT FROM AUTHOR]

The high self-corrosion rate of Mg in aqueous electrolyte generates H 2 , which is the main impediment to restrict the utilization of Mg-air batteries. However, organic/inorganic hybrid electrolyte is prone to reduce the Mg degradation. Herein, the effect of different ethanol fractions in water with 0.6 M NaCl on corrosion behavior of Mg and battery discharge performances is demonstrated. The significant corrosion inhibition in a high content of ethanol (≥20 vol%) in electrolyte is attributed to the formation of a thinner, more corrosion protective layer enriched in magnesium oxide as demonstrated by scanning electron microscopy, X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. Contrarily, in water-based electrolyte a thick, porous and rough layer principally composed of magnesium hydroxide is formed. By varying the ethanol to water fraction in the electrolyte in full battery cell, it is shown that even a small ethanol content (≤ 5 vol%), can greatly enhance the electrochemical performances of Mg anode. Within several ethanol content, 0.5 vol% demonstrates the best performances with a limited corrosion rate and greatly improves the discharge performance and the battery lifetime. It is demonstrated here that application of inorganic/organic dual electrolyte is a promising and easy way towards a well-controlled Mg anode reactivity and improved performances of Mg-air battery. [Display omitted] • Significant corrosion inhibition in high content of ethanol (≥ 20 vol%). • Formation of a thinner, more corrosion protective layer enriched in MgO in presence of ethanol. • Growth of a thick, porous and rough layer composed of Mg(OH) 2 in water-based electrolyte. • The best discharge performance and battery lifetime in 0.5 vol% ethanol content. [ABSTRACT FROM AUTHOR]

The oxidation of Cu 0.7 Zn 0.3 (111) exposed to O 2 at low pressure (7.0 × 10 − 7 mbar) and higher pressure (1 mbar) both at 400 K has been investigated by photoelectron spectroscopy. The results evidenced a preferential oxidation of Zn at the surface in agreement with the literature and Zn segregation to the surface. Moreover, a systematic fitting procedure of high-resolution spectra enabled us to decompose the Zn 2p core-level peak into metallic and oxide components in order to follow the growth of the oxide. By combining these results with careful analysis of the Zn L 3 M 45 M 45 Auger transition, we evidenced the formation of a discontinuous ZnO layer (3D ZnO islands) in both pressure conditions. Measurements of the O 1s peak for two photon energies using synchrotron radiation allowed us to identify interface and bulk components. Changes in the Zn 3d level and valence band during the initial steps of oxidation were also followed. We show that not only thermodynamics but also kinetic effects have to be considered to describe this complex oxidation process. The importance of the role played by the structural quality of the sample on the composition, growth kinetic and structure of the surface oxide layer is evidenced. [ABSTRACT FROM AUTHOR]

Spectroscopic(XPS, ToF-SIMS) and microscopic (SEM, AFM) analyticalmethods have been applied to iron oxide (∼Fe2O3) using a thin film approach to bring new insight into theaging mechanisms of conversion-type anode materials for lithium-ionbatteries. The results show that repeated lithiation/delithiationcauses both chemical and morphological modifications affecting theelectrochemical performance. The SEI layer formed by reductive decompositionof the electrolyte remains stable in composition (mostly Li2CO3) but irreversibly thickens upon multicycling. Irreversibleswelling of the material accompanied by penetration of the SEI layerand accumulation of non-deconverted material in the bulk of the oxidethin film occurs upon repeated conversion/deconversion. After initialpulverization of the thin film microstructure, grain growth and aggregationare promoted by multicycling. This leads to capacity increase in thefirst few cycles, but upon further cycling volume expansion and accumulationof non-deconverted material lead to deterioration of the electrodeperformances. [ABSTRACT FROM AUTHOR]

Abstract: The morphological and chemical modifications induced by repeated cycling of conversion-type negative electrode material were studied for iron sulfide thin films in 1M-LiClO4/PC by combining AFM, XPS and ToF-SIMS analysis with electrochemical control. The topographical changes were consistent with irreversible swelling of the material caused by repeated volume expansion/contraction. A 3% capacity fading measured after 9 conversion/deconversion cycles resulted mainly from the loss of electroactive material forming pinhole defects in the thin film electrode. Repeated cycling caused increasing accumulation of non deconverted material in the bulk thin film electrode. Repeated cycling also resulted in continuous surface up-take and increasing accumulation of the SEI layer in the bulk thin film electrode, rich in Li2CO3. Formation of a duplex-like structure with organic and inorganic compounds primarily distributed in the outer and inner parts, respectively, was suggested by ToF-SIMS depth profiling of the SEI layer. [Copyright &y& Elsevier]

Abstract: A comparative study by Time-of-Flight Secondary Ions Mass Spectrometry and X-ray Photoelectron Spectroscopy, i–E polarization curves and Electrochemical Impedance Spectroscopy of the corrosion protection of low alloy steel by 50nm thick tantalum oxide coatings prepared by low temperature Atomic Layer Deposition (ALD) and Filtered Cathodic Arc Deposition (FCAD) is reported. The data evidence the presence of a spurious oxide layer mostly consisting of iron grown by transient thermal oxidation at the ALD film/substrate interface in the initial stages of deposition and its suppression by pre-treatment in the FCAD process. Carbonaceous contamination (organic and carbidic) resulting from incomplete removal of the organic precursor is the major cause of the poorer sealing properties of the ALD film. No coating dissolution is demonstrated in neutral or acid 0.2M NaCl solutions. In acid solution localized corrosion by pitting proceeds faster with the ALD than with the FCAD coating. The roles of the pre-existing channel defects exposing the substrate surface and of the spurious interfacial oxide promoting coating breakdown and/or delamination are emphasized. [Copyright &y& Elsevier]

Abstract: Combined analysis by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), X-ray Photoelectron Spectroscopy (XPS), polarization curves and Electrochemical Impedance Spectroscopy (EIS) of the relation between chemical architecture of thin (10 and 50nm) chromium and tantalum oxide coatings grown by filtered cathodic arc deposition (FCAD) on carbon steel and their corrosion protection properties is reported. Pre-etching in the deposition process allows reducing the substrate native oxide layer to traces of iron oxide. A carbidic interlayer is then formed by reaction between the first deposited metallic particles and the residual carbon surface contamination of the alloy. The bulk coatings mostly consist of Cr2O3 or Ta2O5 with no in-depth variation of the stoichiometry. Surface and bulk of the coatings are contaminated by hydroxyl and organic groups. The 50nm coating has a relatively large porosity assigned to a columnar growth preventing good sealing at grain boundaries. The duplex structure (Ta/Ta–C) of the carbidic interlayer promotes a less defective growth of tantalum oxide than the single Cr–C interlayer for chromium oxide, thereby improving the sealing properties. The dielectric constants suggest poor insulating properties in line with a defective and porous nanostructure of the coatings. No dissolution was observed for both oxide nanocoatings in neutral 0.2M NaCl. Penetration of the electrolyte and access to the interface with the carbon steel surface cause the dissolution of the Cr–C interlayer, but not that of the Ta/Ta–C interlayer, and a more rapid initiation of localized corrosion. [Copyright &y& Elsevier]

Abstract: A corrosion mechanism is proposed for Al3Mg2, based on electrochemical tests, XPS, and depth profiling using XPS and ToF-SIMS. After short (∼2min) solution exposure, the surface consists of a surface film above dealloying. The dealloying is attributed to selective Mg dissolution and the surface rearrangement of Al into islands, although the metallic Al could alternatively be formed by two reduction reactions. The surface film thickness was ∼10nm. After exposure to ultra-pure water, the composition was AlMg1.3O0.2(OH)5.1 corresponding to Al(OH)3·1.1Mg(OH)2·0.2MgO. After exposure to 0.01M Na2SO4, the composition was AlMg0.2O0.4(OH)2.5 corresponding to Al(OH)3·0.1Al2O3·0.2MgO. Longer exposure produced a thicker surface film, more pronounced metallic Al islands and more MgH2. Three possibilities are identified for MgH2 formation. Al(OH)3 formation is attributed to a precipitation reaction. Bulk nanoporous Al3Mg2 formation is predicted to be possible by Mg dealloying of Mg17Al12. [Copyright &y& Elsevier]

Abstract: Ultra-thin Cr2O3 films (12.0, 17.3 and 29.6nm thick) were produced on Cr metal by thermal oxidation, and their electrochemical properties in 1M LiClO4 in propylene carbonate (PC) were investigated by cyclic voltammetry and chronopotentiometry. The reductive electrolyte decomposition and the conversion/deconversion process were observed and analyzed by X-ray photoelectron spectroscopy (XPS), polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The initial irreversible capacity due to the reduction of electrolyte and the incomplete deconversion process during the first cycle is 70% of the first discharge capacity. A stable charge/discharge capacity of 460mAhg−1 was obtained in the 3rd to 10th cycles. XPS and PM-IRRAS evidenced the growth of a solid electrolyte interphase (SEI) layer that is constituted of Li2CO3 formed by reductive decomposition of the electrolyte. The SEI layer thickness and/or density is modified by the conversion/deconversion reaction. ToF-SIMS evidenced the volume expansion/shrink resulting from the conversion/deconversion reaction. ToF-SIMS also revealed an incomplete conversion process limited by mass transport, which partitions the oxide into a converted outer part assigned to Li2O containing Cr traces and an unconverted inner part ascribed to Cr2O3 or lower Cr oxide containing Li. It was found that the deconversion re-homogenizes the oxide film in a single layer but with lithium trapped in it. The present study provides a detailed understanding of the interfacial reaction on the oxide anode undergoing a conversion/deconversion reaction. [Copyright &y& Elsevier]

[Display omitted] • No significant evolution of the oxide thickness induced by acid pre-treatment. • Important Cu enrichment at the oxide/metal interface after acid pretretment. • The highest Cu enrichment in H 2 SO 4 : Cu0 at interface & Cu oxide in the oxide layer. • IMPs: total dealloying in HNO 3 /H 2 SO 4 & partial removal in HNO 3 bath. • Formation of Cu-rich remnant & possible Cu redeposition after H 2 SO 4 treatment. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to analyse the surface modifications of AA-2024-T3 induced by model pre-treatment baths such as H 2 SO 4 , HNO 3 , and in a mixture of both acids. These acids are commonly used for pickling treatment, applied before conversion coating deposition. ToF-SIMS and XPS measurements showed a significant copper enrichment in metallic and oxidised states, localised at the oxide/metal interface. The sulphuric acid treatment led to the highest Cu enrichment. A lower dissolution rate of AA-2024 was observed by inductively coupled plasma optical emission spectroscopy (ICP-OES). It was concluded that the surface enrichment in Cu is mainly associated with dealloying of intermetallic particles by selective dissolution of the less noble elements. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermal pre-oxidation effects on passive film properties studied on stainless steel. • Combined surface analytical and electrochemical approach applied with closed transfer. • Thermal pre-oxidation improves corrosion resistance at active/passive transition. • Thermal pre-oxidation promotes the enrichment of molybdenum and chromium. • Thermal pre-oxidation enhances growth of the inner layer after anodic passivation. A combined X-ray photoelectron spectroscopy, time-of-fight secondary ion mass spectrometry and electrochemical approach was used to investigate the mechanisms of molybdenum and chromium enrichment of a passive film formed on a model austenitic stainless steel single crystal in aqueous acid media and the effect that thermal pre-oxidation at 250 ° C plays in the composition, thickness and stratification of the film. A clean FeCrNiMo (1 0 0)-oriented surface, prepared under ultra-high vacuum (UHV), was exposed to ultra-low pressures of oxygen at 250 ° C, forming a thin oxide film, rich in iron and chromium, as well as containing molybdenum. An argon-filled glovebox, directly attached to the UHV system, allowed for electrochemical alterations to be carried out without exposure to ambient air. After being held at open circuit potential for 30 min, hydroxylation of chromium and molybdenum was promoted, with a marked enrichment of both elements in the oxide film. A distinct bilayer film was observed. Anodic polarisation resulted in a significant growth of the inner layer and further enrichment of chromium. Pre-oxidation at 250 ° C, using an ultra-low pressure of oxygen, was found to promote protection against transient active dissolution during anodic passivation, and to cause enrichment of molybdenum in the outer layer of the passive film. [ABSTRACT FROM AUTHOR]