Passive Oxide Film Research Articles

Elucidating the effect of strain path-dependent crystallographic texture evolution on the electrochemical behavior of nanostructured AA2024 aluminum alloy

This research provides insight into the effect of strain path-dependent texture evolution on the electrochemical behavior of nanostructured AA2024 aluminum alloy in a phosphate buffer solution (pH = 8.3). To achieve this, AA2024 alloy sheets were processed using two methods: accumulative roll bonding (ARB) and cross accumulative roll bonding (CARB), i.e., rotating the sheets 90° around the normal direction (ND) axis between each cycle. The ARB-processed AA2024 alloy exhibited a pancake-shaped structure and included texture components of Copper {112}<111>, Brass {011}<211>, P {110}<221>, and S {123}<634>. Meanwhile, the CARB-processed AA2024 alloy had extremely fine and equiaxed nano-grains (< 100 nm) and texture components of S {123}<634>, Brass {011}<211>, Goss {011}<100>, Rotated Cube {001}<110>, and P {110}<221> after eight cycles. Electrochemical studies demonstrated an increase in corrosion current density due to high imposed strains in the ARB route, which in effect made the conditions of passive layer formation more difficult and lowered the corrosion resistance. Additionally, achieving a more uniform distribution of extremely fine grains and {011} orientation textures such as Brass {011}<211>, Goss {011}<100>, and P {110}<221> texture components in the CARB route, provided ideal conditions for forming oxide passive films with superior protection properties compared to ARB. These unique findings can contribute to the broader application of crystallographic-orientation-dependent electrochemical behavior of alloys in the field of corrosion management.

Corrosion Inhibition of Carbon Steel in Neutral Chloride Solutions Using Salts of Primary Bile Acids.

Due to growing environmental concerns and regulatory pressures, the demand for environmentally friendly corrosion inhibitors has increased. Biosurfactants are biodegradable and have a low toxicity. However, very few studies have reported on their potential use as corrosion inhibitors. The present study reports the novel application of two bile salts (sodium cholate NaC and sodium chenodeoxycholate NaCDC) as environmentally friendly corrosion inhibitors for carbon steel in a neutral 20 mM NaCl solution. The results of potentiodynamic polarization and electrochemical impedance measurements showed that when added at a concentration of 5 mM, the corrosion inhibition efficiencies of NaC and NaCDC were about 60% and 85%, respectively. The poor inhibitory character of NaC was confirmed by XPS analysis, revealing the formation of oxidative corrosion products on the steel surface. For the steel sample immersed in the solution containing NaCDC, the XPS measurements showed clear evidence of the presence of an organic layer and a passive oxide film on the steel surface. While the steroidal skeleton of NaC is characterized by marked biplanarity (considering its hydrophobic and hydrophilic faces), NaCDC features a steroidal ring with a hydrophilic edge (it does not exhibit biplanarity). Thus, the self-assembly and adsorption behavior of these bile salts on the steel surface are different, leading in the case of NaCDC to form a densely packed protective organic layer.

Dynamic assessment of titanium surface oxides following mechanical damage reveals only partial passivation under inflammatory conditions

Motivated by clinical problems of titanium implant degradation, we developed a workflow that enabled assessment of surface oxide dynamics as a function of clinical interventions and inflammation conditions. We found that mechanical damage led to decrease of stoichiometric TiO2 ratio in the passivation oxide film and further resulted in accelerated degradation under inflammatory anaerobic conditions. This method can be employed for the assessment of surface oxides to monitor implant safety.

Tribocorrosion behaviour of CoCrMo in simulated body fluid under anaerobic conditions

CoCrMo has been used as an implant material for a long time due to its excellent combination of strength, corrosion resistance and biocompatibility. The formation of a thin passive oxide film on the surface of the material plays a crucial role in its performance. This passive film can be ruptured during contact between two surfaces, but usually reforms in short timescales. However, the reformation of the film depends on the availability of oxygen in the surrounding fluid. The oxygen level in human tissue, cartilage and synovial fluid, around which the implant is situated, is much lower than that in laboratory testing under open-air conditions. Moreover, the local oxygen concentration and pH values in the body vary from patient to patient, depending on the patient's health condition and other factors, which leads to variation in the corrosion resistance of metallic implants. Therefore, an implant that performs well at one time may still experience an undesirable level of corrosion at another. Thus, evaluation of the tribocorrosion of implant materials carried out in open-air conditions does not reflect the actual process the implants undergo once in the body, particularly if there is irritation due to injury or surgery. In this study, we investigate the tribocorrosion behaviour of CoCrMo in bioactive solutions under fully aerobic to anaerobic conditions with varying loads/contact pressures. The anaerobic condition leads to a reduction in wear rate and a reduction in the extent of tribofilm formation but does not have an appreciable effect on friction. The mechanisms are discussed in detail.

Optimization of surface oxide chemistry for enhanced corrosion resistance of AlMnFeCoNi – Carbon nanotube composite coatings

AlMnFeCoNi high entropy alloy (HEA) composite coatings with different volume fractions of carbon nanotubes (CNTs) (from electrolyte bath with 2.5, 4, 5, 15, 17.5, 20 mg/L of CNT) were electrodeposited onto mild steel. Corrosion rate of HEA-CNT coatings exhibited non-monotonic variation with increasing CNT volume fraction. Corrosion resistance initially increased and then decreased with increasing CNT addition. Highest corrosion resistance exhibited by coating produced from 5 mg/L of CNT was due to higher surface uniformity, least surface roughness (732 ± 2.92 nm), induced hydrophobicity (115.44 ± 0.29˚) and presence of stable passive oxide films (Al3+, Co2+, Fe3+).

Morphological stability of electrostrictive thin films

A large electric field is typically present in anodic or passive oxide films. Stresses induced by such a large electric field are critical in understanding the breakdown mechanism of thin oxide films and improving their corrosion resistance. In this work, we consider electromechanical coupling through the electrostrictive effect. A continuum model incorporating lattice misfit and electric field-induced stresses is developed. We perform a linear stability analysis of the full coupled model and show that, for typical oxides, neglecting electrostriction underestimates the film’s instability, especially in systems with a large electric field. Moreover, a region where electrostriction can potentially provide a stabilizing effect is identified, allowing electrostriction to enhance corrosion resistance. We identified an equilibrium electric field intrinsic to the system and the corresponding equilibrium film thickness. The film’s stability is very sensitive to the electric field: a 40 percent deviation from the equilibrium electric field can change the maximum growth rate by nearly an order of magnitude. Moreover, our model reduces to classical morphological instability models in the limit of misfit-only, electrostatic-only, and no-electrostriction cases. Finally, the effect of various parameters on the film’s stability is studied.

A corrosion failure analysis of a titanium tank used for production and storage of molten sodium sulfide

The corrosion failure of a titanium tank operating under high temperature of 220 °C for the production and storage of molten Na2S was thoroughly analyzed in this study. The various materialcharacterization methods, such as visual inspection, microscopic observation, chemical analysis, and mechanical assessment, demonstrated that hydride-inducedembrittlement plays a considerable role in the failure of the titanium tank. The key finding was that side products of H2, H2S, and Na2SO3 cause the destruction of the passive oxide film and, thus, provide the conditions for the absorption and penetration of atomic hydrogen, resulting in the formation of brittle TiH2 and subsequent flaking on the surface. To failure prevention of the titanium tank in such environments, the selection of tank material from Monel®400, blowing nitrogen gas into the system, and loading Na2CO3 into the reactive media were proposed. By complementary electrochemical investigations, it was clarified that Na2CO3 can stabilize the passive oxide film on the titanium surface and, therefore, enhance the resistance of the titanium tank against corrosion and failure. Notably, the present study can provide helpful references for enhancing the safety maintenance management of similar types of equipment.

XPS study on passivation behavior of naturally formed oxide on AlFeCuCrMg1.5 high-entropy alloy

High-entropy alloys have exceptional oxidation resistance due to their passive oxide film. In this study, photoelectron spectroscopy was used in a modern atomic-scale in situ initial oxidation analysis process to determine the oxidation behavior and elemental variation on its breakdown. Furthermore, the behavior of natural oxide formed on the AlFeCuCrMg1.5 HEA after the exposure of the alloy to the atmosphere for one hour, one day, and seven days was investigated in detail. Through a survey scan, the elements present on the oxidized surface were determined and quantified. Additionally, the seven-day-exposed HEA was depth-profiled and discovered drastic modifications in the alloy.

The Effect of Cold Rolling on the Corrosion Behaviour of 5083 Aluminium Alloys

Aluminium–magnesium alloys find widespread application in diverse industrial and technological fields owing to their unique characteristics such as lightweight nature, favourable physical and mechanical properties, corrosion resistance and cost-effectiveness. During production, these alloys often undergo various forming processes that significantly affect the morphology and microstructure of their surface layers. Consequently, the surface properties, including corrosion resistance, are notably influenced by these treatments. In this study, the impact of cold rolling on the corrosion behaviour of the 5083 aluminium alloy, which is considered as an important alloy for the aerospace and naval industry, was investigated. The 5083 Al alloy underwent a cold-rolling process, resulting in specimens with reduced average thicknesses of 7% and 15%, respectively. The microstructure of the alloy was examined by using X-ray diffraction, optical and scanning electron microscopy techniques. Furthermore, the corrosion behaviour of both the as-received and cold-rolled aluminium alloy specimens was evaluated through potentiostatic and potentiodynamic corrosion measurements. The experimental results demonstrated that higher cold deformation percentages, within the specified experimental parameters, led to an enhanced corrosion resistance for the alloy. This improvement was primarily attributed to the reduction in grain size induced by recrystallization and to the formation of a passivating aluminium oxide film.

The Enigma of Titanium Electrodeposition on Various Substrates

Titanium is an oxiphilic reactive metal which readily forms passive oxide films onto substrates. The unique properties of the metal such as low density (d=4.5 g/cm3), high strength, and corrosion resistance in harsh environments offers practical advantages. The pure metal is used abundantly in aerospace, armors, submarines, missiles, biomedicals, golf clubs and special electronic applications. The electro-deposition of corrosion resistant coatings is imperative to protect base metals. A review of previous literature has indicated that methods such as roll-diffusion cladding, magnetron discharge sputtering, electron beam, vacuum evaporation, ion beam enhanced deposition (PVD), thermal spray, chemical conversion coatings etc. have been employed in special applications at a prohibitive cost. Plating of titanium films in molten salts at high temperature, and inert atmospheres is a challenge to follow stringent conditions. Electroplating in ionic liquids is extremely expensive and limited.It will be an important technological advancement if a feasible electrodeposition process for titanium is developed for light base metals and plastics in aqueous or semi-aqueous solutions. Titanium electrodeposition in aqueous systems is not a straight-forward process due to its far negative reduction potential than that of hydrogen. Its multivalence states, stability, limited potential range, gas evolution, and substrate passivation pose technical challenges. The present author has critically evaluated several recipes cited by Russian literature, and a few United States patents. Unfortunately, we could not substantiate their cited claims. We have developed an innovative and proprietary process for electro-deposition of Ti in aqueous and partially non-aqueous systems. Deposition of titanium and its alloy films is demonstrated on variety of substrates such as Steel, Pb, Zn, Al, and selected plastics. It is our hope that this endeavor will open new avenues in surface finishing applications.

(Digital Presentation) Construction of a Novel Phosphate Potential Sensor and Its Application

Phosphorus content is one of important indicators in the evaluation of water quality. The level of phosphorus in oilfield water systems not only affects the overall water cycle production system, but excessive phosphorus wastewater entering the environment can cause eutrophication of the water body, as can high levels of ammonia and nitrogen, and leading to rapid growth of algae and thus affecting the balance of the aquatic ecosystem. Therefore, the regulation of phosphorus is of great importance. Phosphorus exists in nature mainly in the form of phosphate, which is currently detected by the traditional spectrophotometric method. As this method requires the addition of a large number of chemical reagents, it is not only complex and time consuming, but also produces a waste solution at the end of the test that can easily cause secondary pollution to the environment. Compared to traditional methods, Ion Selective Electrodes (ISEs) are easier to use, more sensitive, less expensive and do not cause secondary contamination. In conventional ion selective electrode detection systems, liquid contact ion selective electrodes consisting of a polymeric ion selective membrane, an internal filling fluid and an internal reference electrode are susceptible to common variables such as pressure and temperature. There are problems with complex maintenance, leakage and signal calibration. In contrast, all-solid ion-selective electrodes that eliminate the internal filling fluid and internal reference have become a hot research topic for such potential-based sensors. In this thesis, the following research was carried out with the aim of developing a phosphate potentiometric sensor with practical detection capabilities:(1) PANI/ITO electrodes were produced by electrodeposition of polyaniline on ITO conductive glass by constant potential deposition and by ultrasonic peeling. Three oxidation states of PANI/ITO electrodes were prepared at different voltages using phosphoric acid as the doping solution. LBPANI/ITO electrode in the fully reduced state, ESPANI/ITO electrode in the semi-oxidized state and PBPANI/ITO electrode in the fully oxidized state. The response sensitivity and stability of the three electrodes were investigated to determine the optimum doping potential; the response performance of the electrodes was tested for different doping times to determine the optimum preparation time. It is shown that the PBPANI/ITO electrode in the fully oxidized state has the optimum stability and response sensitivity at a doping time of 80 s. The electrode showed good linear response in the range of 1.00x10-5 ~ 1.00x10-1 M, with a response sensitivity of 37.30 dec/mV (R2 = 0.9966) and a detection limit of 10-5.6 M. The response time of the electrode to the solution was around 4 s, and it had good acid-base adaptability (pH 4.0 ~ 8.0). The performance of the prepared PBPANI/ITO electrode as a potentiometric phosphate sensor was also investigated in terms of stability (n = 10, RSD 1.76 %) and lifetime (6 weeks at room temperature), and was successfully used for phosphate detection and analysis in oilfield re-injection water, lake water and tap water samples in real environments with satisfactory results. (2) To further prepare a phosphate potential sensor with a high sensitivity response. We pretreated the home-made cobalt electrode with high pressure anodic oxidation in sodium hydroxide solution to produce a uniform cobalt oxide passivation film on the electrode surface. The sensitivity and stability of the response of the electrode at different pretreatment times were investigated to determine the optimum preparation conditions. The results showed that the pretreated cobalt electrode had a good response in the range of 1.00x10-5 ~ 1.00x10-1 M. The response sensitivity was 67.22 mV dec, R2 = 0.9939 and the detection limit was 10-5.5 M. It was much higher than that of the untreated cobalt electrode. This far exceeded that of the untreated polished cobalt electrode (36 ~ 40 mV/dec). The performance of the pretreated cobalt electrode as a potentiometric phosphate sensor was also investigated in terms of lifetime (7 weeks at room temperature), response rate (less 40 s), stability (n = 10, RSD 1.07 %) and acid-base adaptability (pH 4.0 ~ 8.0), and the sensor was successfully used for phosphate in oilfield re-injection water, lake water and tap water samples with satisfactory results.

Influence of dissolved oxygen concentration on the electrochemical and semiconductor characteristics of passive oxide films deposited on Fe-based metallic glass coatings

Certain metals produce passive oxide film layers during use which are closely related to their corrosion resistance. The properties of the oxide film are strongly influenced by the oxygen content of the surrounding environment. This study aims to examine the impact of dissolved oxygen concentration on the corrosion and passive oxide film formed on Fe-based metallic glass coatings. In deoxygenated solutions, the coating was highly susceptible to corrosion, while exhibiting the highest corrosion potential in oxygenated solutions due to the formation of a dense oxide film. The impedance of the passive film was notably influenced by the presence of dissolved oxygen. In deoxygenated solutions, the impedance remained stable and at a minimum level. However, in oxygenated solutions, the impedance exhibited a significant increase accompanied by rapid film growth. The carrier concentration in the passive film remained low and constant in deoxygenated solutions but decreased in oxygenated ones. The composition of the passive film varied with dissolved oxygen concentration, leading to FeOOH formation in deoxygenated solutions and to the increase in Cr2O3/Cr(OH)3 ratio in oxygenated environments. Moreover, deoxygenated solutions slowed down the film growth rate, while oxygenated ones were conducive to the fast development of films, affecting their protective ability.

Corrosion and stress corrosion cracking characteristics of 4043 aluminium alloy fabricated through directed energy deposition process

Additive manufacturing (AM) has emerged as a crucial element of Industry 4.0. In the pursuit of fabricating lightweight components, AM of aluminium alloys has become the centre of focus in recent years. This study investigates aluminium alloy (ER4043) components fabricated by arc-based directed energy deposition (DED-arc) for their corrosion and stress corrosion cracking (SCC) behaviour in 0.6 M NaCl solution at room temperature. Electrochemical characteristics in 0.6 M NaCl solution were investigated using open circuit potential (OCP), potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) tests. Electrochemical results revealed that the DED samples fabricated using a tungsten inert gas (TIG) welder as the energy source demonstrated better resistance against corrosion when compared to those developed through cold metal transfer (CMT) based DED. The prolonged exposure of samples in 0.6 M NaCl facilitated the growth of a stable passive oxide film leading to enhanced corrosion resistance. Slow strain rate tests (SSRT) conducted in air and 0.6 M NaCl solution showed that DED samples are susceptible to SCC. The fractography of the fractured SSRT samples indicated the mode of failure to be intergranular.

Electro-chemo-mechanical properties of anodic oxide (passive) films formed on Cu, Ni and Fe

Abstract Electro-chemo-mechanical properties of anodic oxide (passive) films formed on metals have been reviewed focusing on the results of stress variations caused by anodic oxidation of Cu, Ni, and Fe thin film electrodes in deaerated pH 8.4 borate buffer solution at 25 °C. The surface stress varies toward compressive direction due to adsorption of OH on Cu from aqueous solution as well as adsorption of oxygen on metals from gas phase. The stresses are generated with the growth of three-dimensional anodic oxide films on metals. The magnitude and sign (tensile or compressive) of the intrinsic film stress were determined by taking the residual stress of the substrate and the dielectrostriction into consideration. The tensile or compressive intrinsic film stress depends on p-type or n-type semiconductive properties of the anodic oxide films, which is explained in terms of the void formation or oxide formation in the metal side at the metal/film interface. Furthermore, the stress variation toward compressive direction during cathodic reduction of the anodic oxide films is explained in terms of the volume expansion due to the formation of intermediate species.

Effect of Fluorides on the Corrosion Properties of Titanium Mini-implants: A Systematic Review

Objective: This systematic review plans to evaluate the effects of fluoride ions on the corrosion properties of titanium mini-implants. Background: Mini-implants are broadly used in orthodontics as an alternative to traditional intraoral anchorage. They comprise of Ti-6Al-4V with a passive oxide film of titanium dioxide for high corrosion resistance properties. To maintain oral hygiene orthodontic patients are often prescribed fluoride mouth rinses, toothpastes, etc, which might affect the corrosion resistance properties of mini-implants. Materials and methods: A literature search by means of proper MeSH terms and PICO format was done using the following databases: Google Scholar, PubMed, and EBSCO HOST. The following studies will be included- Randomized Controlled Trials, Observational studies, In-vivo studies, In-vitro studies, Clinical studies, and Human studies on the corrosion of titanium mini-implants subjected to fluorides. Exclusion criteria included surveys and questionnaire-based studies, review letters, personal opinions, book chapters, and conference abstracts. Results: A total of 134 articles were obtained, and 5 were selected for inclusion in the review. Results showed that fluoride ions significantly dropped the corrosion resistance properties of titanium. Conclusion: The acidic environment due to low pH and increase in the fluoride ion concentration seems to directly affect the corrosion resistance properties of titanium mini-implants, and attention must be paid while prescribing fluoride agents when titanium mini-screws are used.

Effect of compressive stress on corrosion protection performance of phytic acid conversion coating on carbon steel

As an environmentally friendly organic coating, phytic acid conversion coating (PACC) has been widely used for the protection of metals. In this study, the evolution of PACC on carbon steel under compressive stress is studied via multiple electrochemical and morphological approaches. Interestingly, electrochemical results show that a strengthening effect on PACC can be found when proper stress is applied, which is much distinct from the rule for oxide passive films. The proper compressive stress can effectively improve the corrosion protection performance of PACC, thus enhancing the corrosion resistance of carbon steel to chloride attack. As the applied stress increases, a detrimental effect is confirmed for compressive stress on the PACC layer. The protective PACC layer with the highest protection efficiency and coating adhesion is obtained at 100 MPa. In combination with the observations of SEM/XPS, a three-stage model is proposed to illustrate the evolution of PACC under compressive stress. In the natural stage, numerous cracks form in the PACC layer. In the strengthening stage, the PACC layer is compacted and the cracks in it are greatly healed. In the weakening stage, buckles and partial shedding emerge due to the overlarge stress.

Enhancing Surface Integrity of Micro-Holes Machined on Inconel 718 using Shaped Tube Electrochemical Machining via Hydroxide Mixing

This research explores enhancing surface integrity of high aspect ratio (AR>5) micro-holes machined on Inconel 718 using Shaped Tube Electrochemical Machining (STEM) by mixing limited amount of metal hydroxides in the different electrolyte solutions. Typically, STEM employs hazardous acid solutions. These solutions cause machine corrosion, environmental risks, and harm to operators. This research aims to explore eco-friendly and safe alternatives. The efficacy of adding NaOH or KOH to eco-friendly neutral aqueous solutions of NaCl, KBr, and NaNO3 on machined surfaces is expounded. We assess electrolyte mixing parameters, including concentration and composition, and explore the effects of varying electrolyte temperature, voltage, and tool feed rate. Surface assessment uses SEM, EDX, XRD, and profilometry. Results reveal that adding hydroxides to neutral salt solutions improves surface roughness and reduces pitting. Hydroxide ions aid in dissolving oxide films during STEM of Inconel 718. Under specific conditions (9 g l−1, 18°C, 8 V, 0.8 mm min−1), NO3│OH yielded the lowest Ra (1.64 μm), while Br│OH resulted in the highest Ra (2.14 μm) with pitting, cracks, and deposits. NO3│OH exhibited a 25% decrease in Ra when a hydroxide concentration rise from 3 g l−1 to 15 g l−1. This research supports eco-friendly STEM for improved surface quality without process performance compromise.

Interphase corrosion inhibition mechanism of sodium borate on carbon steel rebars in simulated concrete pore solution

Sodium borate (Na2B4O7) corrosion inhibition mechanism was studied on carbon steel rebars in 0.6 mol/L Cl– simulated concrete pore solution (SCPS) at different temperatures and concentrations. Electrochemical testing including cyclic potentiodynamic polarization (CPP), electrochemical impedance spectroscopy (EIS), and Mott–Schottky plots were utilized to understand the influence of inhibitor concentration and temperature on the thermodynamics of the adsorption and activation processes. It was found Na2B4O7 imparts corrosion protection due to the formation of a 3D Fe–B–O stable interphase passive film, achieving an inhibition efficiency up to 86%. This can be attributed to the film having a lower donor current density and less vacancies, according to the Mott–Schottky tests. The formed interphase passive film was more stable and compact with less point defects compared to the blank due to Na2B4O7 adsorption, this phenomenon was substantiated using the atomic packing factor, film thickness, and Mott–Schottky plots. It was revealed, using adsorption isotherms, that Na2B4O7 interacted with the surface via physiochemical adsorption, creating a thinner/compact passive film composed of a rhombohedral calcite-type structure. SEM, XRD, and XPS were used to illustrate that Na2B4O7 aides in the formation of a stable double-layered net structure Fe2O3/FeBO3 passive oxide film. Finally, an interphase corrosion inhibition mechanism of Na2B4O7 was proposed.

Atomistic insights on enhanced passivity: DFT study of substitutional Mo on Cr2O3 and Fe2O3 surfaces

Substitution of a metal cation by Mo and its effects on vacancy formation on (0001)-oriented chromia and hematite surfaces were studied using DFT calculations to provide atomistic insights on the experimentally observed Mo-enhanced passivity. The substitution is favoured energetically, resulting in Mo more enriched in the Fe-rich than in the Cr-rich oxide zones in passive oxide films. The presence of substitutional Mo disfavours the formation of O vacancies and favours metal vacancies, more significantly in Fe2O3 than in Cr2O3, suggesting a prevention of passivity breakdown in chloride-rich environment and a cure of the Fe-rich weak sites of passivity by Mo.

The anaerobic corrosion of the carbon steel overpack under anoxic alkaline conditions representing the Belgian supercontainer concept

Abstract. The Belgian Agency for Radioactive Waste and Enriched Fissile Materials (ONDRAF/NIRAS) is responsible for the management of all radioactive materials (currently existing and future waste) generated in Belgium. Disposal in deep stable geological formations is, at present, accepted at an international level to be the most promising option for the long-term management of high-level and/or long-lived radioactive waste. ONDRAF/NIRAS currently recommends underground disposal in a geological stable and poorly indurated clay formation as the reference management option to steer their RD&amp;amp;D research programmes. The supercontainer concept is currently being considered as the reference design for the final disposal of vitrified high-level radioactive waste (VHLW) and spent fuel (SF) in Belgium. It comprises a prefabricated Portland cement-based buffer that completely surrounds a carbon steel overpack. In this highly alkaline environment (pH ∼ 13.6), and under normal conditions (i.e. without the ingress of aggressive species), the carbon steel overpack will be protected by a passive oxide film, which is expected to result in very low uniform corrosion rates. The main goal of the ongoing R&amp;amp;D corrosion studies performed at ONDRAF/NIRAS is to provide confidence that the integrity of the carbon steel overpack will not be jeopardized at least for the duration of the thermal phase. Considering the long timescales applicable to waste disposal, determining accurate and reliable estimates of the uniform corrosion rate under anoxic conditions forms a very important part of the R&amp;amp;D methodology of ONDRAF/NIRAS' corrosion programme. On the other hand, the occurrence of localized forms of corrosion cannot be neglected, and therefore it is also crucial to demonstrate that no other form of corrosion apart from uniform corrosion can take place. This paper gives an overview of the status of the research performed at ONDRAF/NIRAS with respect to the uniform corrosion, pitting corrosion and stress corrosion cracking behaviour of the carbon steel overpack of the supercontainer.