Electrochemical Noise Resistance Research Articles

A Comparative Study of the Corrosion Behavior of P110 Casing Steel in Simulated Concrete Liquid Containing Chloride and Annulus Fluid from an Oil Well

The corrosion behavior of P110 casing steel in simulated concrete liquid and simulated annulus fluid was investigated to reveal the corrosion pattern and protective properties of corrosion products in the two environments. Potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), Mott–Schottky tests, and electrochemical noise (EN) tests were used to study the corrosion behavior of P110 casing steel in simulated concrete liquid and simulated annulus fluid saturated with CO2. Scanning electron microscopy (SEM) combined with Energy-Dispersive Spectrometer (EDS) mapping was used to characterize the corrosion morphology and elemental distribution of P110 casing steel. The results show that the corrosion resistance of P110 casing steel deteriorates with the increasing immersion days in the simulated annulus fluid, the impedance decreases gradually, and the corrosion-product film shows a loose and porous structure. In the simulated concrete liquid, under the condition of containing a low concentration of Cl−, the protection of the corrosion products gradually increases with the extension of immersion days. With the increasing concentration of Cl− and the extension of immersion days, the electrochemical noise resistance and charge transfer resistance of P110 steel decrease gradually, and the protective property of the corrosion-product film decreases, which is capable of forming steady pitting corrosion.

Development of machine learning techniques in corrosion inhibition evaluation of 5-methyl-1 H-benzotriazole on N80 steel in acidic media

In this study, three machine learning models of data analysis based on multiple linear regression (MLR), multiple nonlinear regression (MNR), and artificial neural network (ANN) has been proposed to model the behavior of 5methyl-1 H-benzotriazole (m-BTA) inhibitor on N80 steel in acidic media at different temperatures and inhibitor concentration. Based on experimental observation, the DC trend removal by Polynomial detrending revealed a suitable trend between electrochemical noise (ECN) measurement data and the results obtained from electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization test at m-Factor equals to 3, 4, and 5. The inhibition efficiency (η) of 91% was achieved by using 0.001 M of m-BTA inhibitor. The corrosion rate will increase by increasing the temperature for the blank sample. Still, the m-BTA resulted in corrosion protection for N80 at high temperatures, and ECN resistance (Rn) increases with increased m-BTA concentration. The experimental tests revealed that temperature and m-factor are significant for corrosion inhibition of m-BTA; also, inhibitor concentration is an essential factor. Therefore, these three parameters were chosen as inputs for the Rn of the inhibitor. Removing unnecessary data from the original dataset causes relevant results compatible with experimental observations. The results of the reduced data set showed that R2 for the test of whole and reduced MLR model is 0.41 and 0.69, respectively, which shows that the reduced model is more suitable for modeling the training data than the whole model. The MNR model presents better accuracy than the MLR model, demonstrating that the relation between inputs and output does not follow a linear dependency. Several topologies of the ANN model were constructed, and the number of neurons was changed in one hidden layer. Finally, five neurons in the hidden layer with the Levenberg–Marquardt backpropagation (LMBP) algorithm were selected to develop the optimum ANN model, which has R2 and RMSE values of 0.99 and 17.41.

Electrochemical and surface characterization studies of winged bean extracts doped TEOS-PDMS sol-gel protective coatings on reinforcing bar in acidic medium

Hybrid sol-gel coatings consisting of tetraethoxysilane (TEOS)-polydimethylsiloxane (PDMS) molecular precursors doped with winged bean extracts were synthesized for the corrosion protection of reinforcing steel in a 0.5 M HCl medium. The incorporation of winged bean extracts doped into hybrid TEOS-PDMS composite coatings on reinforcing steel resulted in a protective system with superior corrosion protection performance, as determined by electrochemical impedance spectroscopy, electrochemical noise measurement and potentiodynamic polarization. When compared to the undoped TEOS-PDMS silanol coating, the corrosion current density and electrochemical current noise resistance values of the winged bean extracts doped hybrid coatings were much lower, whereas charge transfer resistance values were significantly higher. Scanning electron microscopy, Fourier transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy techniques were used to analyse the morphology and structure of developed sol-gel coatings. In addition, atomic force microscopy and wettability analyses were exploited to further understand the characteristics of hybrid silanol coatings. The outcome of this study corroborates that winged bean extracts doped TEOS-PDMS hybrid coatings could be adopted as potential coatings for reinforcing steel.

Effect of Heat Treatment on the Electrochemical Behavior of AA2055 and AA2024 Alloys for Aeronautical Applications

Since their development, third-generation aluminum–lithium alloys have been used in aeronautical and other applications due to their good properties, replacing conventional Al-Cu and Al-Zn alloys and resulting in an increase in payload and fuel efficiency. The aim of this work was to investigate the influence of different heat treatments on the electrochemical corrosion behavior of the alloys AA2055 and AA2024 in the presence of three different electrolytes at room temperature, using an electrochemical noise (EN) technique in accordance with the ASTM-G199 standard. In the time domain, the polynomial method was employed to obtain the noise resistance (Rn), the localization index (IL), skewness, and kurtosis, and in the frequency domain, employing power spectral density analysis (PSD). The microstructure and mechanical properties of the alloys were characterized using scanning electron microscopy (SEM) and the Vickers microhardness test (HV). The results demonstrated better mechanical properties of the AA2055 alloy, which had a Vickers hardness of 77, 174, and 199 in the heat treatments T0, T6, and T8, respectively. An electrochemical noise resistance (Rn) of 2.72 × 105 Ω·cm2 was obtained in the AA2055 T8 alloy evaluated in a NaCl solution, while the lowest Rn resistance of 2.87 × 101 Ω·cm2 occurred in the AA2024 T8 alloy, which was evaluated in a HCl solution. The highest electrochemical noise resistance (Rn) was obtained in the AA2055 alloys, which had received the T6 and T8 heat treatments in the three solutions.

AM60-AlN Nanocomposite and AM60 Alloy Corrosion Activity in Simulated Marine-Coastal Ambience

The initial stages of AM60-AlN nanocomposite and AM60 corrosion behaviors were compared over 30 days of exposure to solution (NaCl, Na2SO4 and NaHCO3), simulating the marine-coastal environment (SME). The incorporation of AlN nanoparticles (1.0 wt.%) in the AM60 alloy matrix favored the lower roughness of the AM60-AlN, associated with the grain refinement in the matrix. During the immersion of the alloys, pH of the SME solution shifted to alkaline values >9, and therefore, the solubility of AlN aluminum hydroxide phases were raised, followed by a slightly higher release of Mg-ions and corrosion rate increase. The chloride ions attributed to the unstability of the Al-Mn phase and Al(OH)3 corrosion product was formed in a low content. The composite AM60-AlN presented lower value of the electrochemical noise resistance (Rn), suggesting that the corrosion process occurs with less difficulty. The localized corrosion near the Al-Mn cathodes seems to be stronger on the composite surface, in area and depth of penetration. The corrosion current fluctuations suggested that the corrosion is a weakly persistent process, dominated by the fractional Gaussian noise (fGn).

The Einstein Fluctuation–Dissipation Relation as Applied to the Analysis of the Electrochemical Noise Resistance

The Einstein Fluctuation–Dissipation Relation as Applied to the Analysis of the Electrochemical Noise Resistance

Electrochemical noise analysis to evaluate the localized anti-corrosion properties of PP/graphene oxide nanocomposite coatings

• Electrochemical noise was used to evaluate the localized corrosion of PP-based NCCs. • PP|Graft|GO = 0.1 illustrated the best localized corrosion performance. • PP|Graft|GO = 0.1 was able to re-passive and prevent the growth of large & deep pits. • In the presence of GO, the transients shift to the higher frequencies at all times. Electrochemical noise analysis was applied to evaluate the localized anti-corrosion performance of polypropylene (PP)-based nanocomposite coatings (NCC). In this regard, the NCCs were developed on mild steel from a solution containing PP, MAH-grafted PP, and different percentages of graphene oxide (GO). The coated samples were subjected to thermal tests, salt spray, and electrochemical noise (EN) analysis. Electrochemical potential and current noise (EPN & ECN) signals were evaluated to find information about localized corrosion. First, the raw signals were analyzed based on the empirical mode decomposition (EMD), then the 3D diagrams (intensity, time, and frequency) were plotted using the Hilbert transform. The results showed in the presence of GO, the transients shift to the higher frequencies at all times, which confirms more tendency to uniform corrosion instead of localized. Introducing 3 wt% of GO NPs into the coating leads to the electrochemical noise resistance increasing by 5 times (>10 8 Ω.cm 2 ), pit initiation rate decreasing, and pit radius reduction (by ∼5 times). As a result, MAH-grafted PP and GO in these NCCs can act as effective barriers against corrosive agents, especially the agents that cause pitting corrosion.

Assessment of durability and zinc activity of zinc-rich primer coatings by electrochemical noise technique

The three-coat system consisting of a zinc-rich primer, epoxy midcoat, and polyurethane topcoat has been widely adopted for corrosion protection of structural steel bridges. Corrosion mitigation is afforded by the barrier characteristics of the various layers as well as beneficial galvanic coupling of the zinc pigments in the primer to the steel substrate when subjected to corrosive environments such as with moisture ingress and coating defects. The dispersed zinc pigments in the binder require adequate electronic coupling in order to provide the beneficial electrochemical coupling of the zinc to the steel. The application of the electrochemical noise (EN) technique to identify coating corrosion performance was reviewed in controlled laboratory tests. Zinc pigment activation and transition to passive-like conditions in defect and defect-free coating specimens could be identified by EN. The characteristic charge of noise events resolved by shot noise analysis was demonstrated to be related to anodic polarization of extended active zinc pigments adjacent to coating defect sites galvanically coupled to the exposed steel and passivated zinc pigments. Electrochemical noise resistance was shown to convey zinc/steel interfacial behavior in cases with sufficient activity but largely reflects coating barrier quality for intact coatings.

The Electrochemical Activity of Mg and Mg-Ca0.3 in Hank’s Physiological Solution

This research reports the electrochemical degradation of Mg and the Mg-Ca (0.3% wt.) alloy up to 14 days of exposure to Hank’s solution as a physiological medium at 37°C. The elemental composition (SEM-EDS) of the formed layer revealed that the intermetallic particles of Mg2Ca-phase appeared on Mg-Ca0.3 surface before and after immersion tests. XPS analysis suggested that the layers formed contain Mg(OH)2, Ca10(PO4)6(OH)2, and CaCO3. The current density fluctuations were considered as electrochemical noise and the result suggest that the corrosion occurs as persistent stationary process. The pitting index (PI) for Mg was two times greater and its electrochemical noise resistance 5.5 lower than those of Mg-Ca0.3. The concentration of the released Mg-ions was ~ 3 times higher for Mg than that of Mg-Ca0.3. The positive effect of Ca may be considered as a consequence of the formed layer, which impedes the cathodic hydrogen evolution and Mg-ions release.

Corrosion effect on reinforced concrete with the addition of graphite powder and its evaluation on physical-electrochemical properties

The corrosion of reinforced concrete without and with the addition of graphite powder with low carbon content was evaluated. Phase identification processes and physical-electrochemical properties of the concrete were analyzed using X-ray diffraction techniques (XRD), scanning electron microscopy (SEM), half-cell potential, electrochemical noise (EN) and linear polarization resistance (LPR). Samples were studied for 168 days in saline solution. The results show that, when adding graphite powder in an amount of 2.5% by weight of cement, the compressive strength increased if compared with the control sample. The electrochemical tests show that the higher the level of graphite replacement, the higher the level of corrosion in concrete.

Electrochemical noise analysis to obtain the Rsn value via FFT using Excel

Electrochemical noise (EN) measurements are based on the fluctuations of the electrochemical potential and the current that occur during, for example, a corrosion process without an external signal perturbation. EN analysis (ENA) allows assessment of the type of corrosion and rapid determination of the corrosion rate. Microsoft Excel®, an inexpensive and readily available software package, is an excellent tool for performing repetitive calculations, with automation that saves time for the users. It is a useful tool for the analysis of EN data using fast Fourier transform (FFT), a process that is often made repeatedly and, if not automated, is quite laborious. This work presents a step-by-step procedure using Excel to perform these calculations, automating the process of obtaining the spectral electrochemical noise resistance, . This routine was used to analyze experimental potential and current noise data recorded for chalcopyrite. The results were comparable to those obtained for the same set of experimental data using Origin® software.

Natural additive (nopal mucilage) on the electrochemical properties of concrete reinforcing steel

In this investigation the effect of Nopal mucilage on the electrochemical properties of concrete was evaluated. Three concentrations of this additive were designed with a Nopal-water ratio of 1:1, 1:2 and 1:3. Compressive tests were performed after 28 days of curing. Specimens were evaluated for 270 days through various electrochemical techniques such as: Open Circuit Potential (OCP), Electrochemical Noise (EN) and Linear Polarization Resistance (LPR). Results indicate a decrease in compressive resistance in samples with Nopal mucilage at 28 days. The onset of steel corrosion was delayed and the corrosion rate was lower for samples with Nopal mucilage. The conservation and storage of this additive before being used in concrete can be a challenge to analyze.

Anticorrosion Behaviour ofRhizophora mangleL. Bark-Extract on Concrete Steel-Rebar in Saline/Marine Simulating-Environment

This paper investigates anticorrosion behaviour of the bark-extract from Rhizophora mangle L. on steel-rebar in concrete slabs in 3.5% NaCl medium of immersion (for simulating saline/marine environment). Corrosion-rate, corrosion-current, and corrosion-potential were measured from the NaCl-immersed steel-reinforced concrete cast with admixture of different plant-extract concentrations and from positive control concrete immersed in distilled water. Analyses indicate excellent mathematical-correlation between the corrosion-rate, concentration of the bark-extract admixture, and electrochemical noise-resistance (ratio of the corrosion-potential standard deviation to that of corrosion-current). The 0.4667% Rhizophora mangle L. bark-extract admixture exhibited optimal corrosion-inhibition performance, η = 99.08±0.11% (experimental) or η = 97.89±0.24% (correlation), which outperformed the positive control specimens, experimentally. Both experimental and correlated results followed Langmuir adsorption isotherm which suggests prevalent physisorption mechanism by the plant-extract on the reinforcing-steel corrosion-protection. These findings support Rhizophora mangle L. bark-extract suitability for corrosion-protection of steel-rebar in concrete structure designed for immersion in the saline/marine environmental medium.

A Complementary Electrochemical Approach for Time-Resolved Evaluation of Corrosion Inhibitor Performance

In this paper, different macroscopic electrochemical techniques are applied to study the corrosion inhibitor efficiency, protection mechanism and stability of a calcium aluminum polyphosphate silicate hydrate inhibitor on hot-dip galvanized steel in the time-domain. Potentiodynamic polarization (PP) measurements are applied to study the anodic and cathodic mechanistic behavior as well as inhibitor efficiencies at discrete and single times of exposure. Open circuit potential (OCP) with superimposed linear polarization resistance (LPR) measurements are applied as a faster, non-invasive alternative to PP, characterizing the overall performance of the system in terms of the polarization resistance. Electrochemical impedance spectroscopy (EIS) measurements are applied to detail both the overall performance of the system as well as the corrosion inhibition mechanism related to the electrochemical system's physicochemical representation over time. Electrochemical noise (EN) measurement are used to evaluate the inhibition efficiency as a function of exposure time, represented by the electrochemical noise resistance. Odd random phase electrochemical impedance spectroscopy (ORP-EIS) is selected as the electrochemical tool to study the system's instability, by evaluation of the non-linearities and non-stationarities over time. The non-stationarities present in the inhibitor-containing electrochemical system are shown to cause the overall instability of the system and should be taken into account when interpreting results from the different techniques over time.

Electrochemical noise assessment of effect of sol parameters on the performance of an eco-friendly silane sol-gel coating on 304L stainless steel

ProposeThis paper aims to access the protective function of hybrid sol-gel coatings deposited on 304L stainless steel substrate in silane solutions containing a mixture of tetraethoxysilane, methyltriethoxysilane and glycidyloxypropyltrimethoxysilane with different pH values during various immersion periods.Design/methodology/approachThe 304L stainless steels coated through 10 and 30 s of immersion in the silane solutions with pH values of 2.1 and 2.8 were exposed to NaCl solution. The corrosion resistance of the coated substrates was studied through taking advantage of electrochemical noise method as well as atomic force microscopy (AFM), water contact angle and field emission-type scanning electron microscopy (FESEM) surface analysis.FindingsThe electrochemical current noise, PSD (I) plot, noise resistance and characteristic charge as parameters extracted from electrochemical noise method indicated the superiority of eco-friendly silane coating deposited on the substrate surface during 10 s exposure to the solution, due to the film uniformity and homogeneity as confirmed by FESEM and AFM. Moreover, immersion of the stainless steel in the silane solution with pH 2.1, characterized by higher hydrolysis ratio, led to more effective corrosion control in the NaCl electrolyte according to the results of electrochemical noise and FTIR measurements.Research limitations/implicationsThe noise resistance and characteristic charge as electrochemical noise parameters were only used in this research to evaluate the protective behavior of the water-based silane sol-gel coatings. Future studies should examine the correlation between electrochemical noise data and the parameters extracted from other electrochemical methods, e.g. electrochemical impedance spectroscopy.Practical implicationsThe data obtained in this research may provide an effective approach based on electrochemical noise method to screen the silane sol-gel coatings for protection of metallic substrates against corrosion.Originality/valueAccording to the literature, no report can be found studying the effect of immersion time on a silane solution, including glycidyloxypropyltrimethoxysilane, tetraethoxysilane and methyltriethoxysilane, as well as the silane solution pH on the corrosion resistance of 304L stainless steel in NaCl solution through electrochemical noise method.

Study of the Inhibiting Efficiency of an ABS Coating Doped with Lansoprazole on Mild Steel

Organic inhibitors have had a great boom in the field of research in the last decade, since they have been reported to be good inhibitors of corrosion by having in their chemical composition atoms of nitrogen, sulfur or oxygen, allowing to be absorbed on the surface of the metal, and for having environmentally friendly characteristics. Polymeric coatings have always been good protectors of corrosion in multiple metals in different solutions. Likewise, this project seeks to help the environment with the recycling of this waste polymer being used in multiple areas, mostly in the automotive industry, generating tons of waste in its manufacturing process. On the other hand, the remains of the expired medicines generate thousands of kilograms of garbage, which later become fuel for cement factories, contaminating the environment in a different way. The aim of this study is to evaluate the corrosion protection of a polymer coating doped with an organic inhibitor extracted from an expired drug on mild steel in alkaline and basic solutions. Electrochemical tests were carried out, such as Electrochemical Impedance Spectroscopy, Electrochemical Noise and Polarization Resistance, and it was characterized by FTIR, XRD, and AFM to confirm the union of both elements. Electrochemical tests shown, that the system coating/inhibitor had good results in the basic solution, maintaining a constant resistance in the time that the test lasted (2000 hours). Likewise, in the alkaline solution, the system coating/inhibitor indicate an offspring in the resistance, obtaining an inferior behavior that the blank. The FTIR and XRD characterization indicate that in the dissolution, there are no chemical reactions that affect the properties or characteristics of each component. In AFM shows that, although there are some pores in the area, the coating is uniform in the entire surface.

Aluminium Corrosion in Bioethanol/Gasoline Blends

In this work, the corrosion behavior of aluminum in different types of bioethanol/gasoline blends has been evaluated by using electrochemical techniques. Evaluated bioethanols included bioethanol from Apple, mango, orange and sugar cane in concentrations of 10 and 20%, whereas employed techniques included electrochemical impedance spectroscopy (EIS), electrochemical noise (EN) and linear polarization resistance (LPR) during 90 days. Corroded samples were analyzed in a scanning electronic microscope (SEM). Obtained results have shown that orange, apple and mango bioethanols/gasoline, in both concentrations, there is a decrease in the impedance value as compared to that for pure gasoline, with the highest corrosion rate exhibited by the sugar cane bioethanol. LPR results indicate that the mango bioethanol/gasolina blends exhibited similar corrosion rates to that exhibited by gasoline. On the other hand, EN measurements showed that in both pure gasoline and the 10% concentration noise reading showed indicating a high susceptibility towards localized type of corrosion, whereas those exhibited by th 20% concentration indicated a susceptibility towards uniform type of corrosion or passivation, which was corroborated by the SEM micrographs.

Corrosion Behavior of Al Alloys By Additive Manufacturing

INTRODUCTION The alloys of (Mg-Si) are not among the most resistant aluminum alloys, but these represent a large part of the aluminum products in the world (approximately 20%), however, they are prone to failure by corrosion. Aluminum tends to be attacked locally in particular by crevice (crevice corrosion) and in areas of stagnation, in which passivity disappears. In recent years, 3D manufacturing technology has become relevant in the manufacturing processes and the printing of alloys has not been the exception. Among the benefits that can be obtained is an improvement in the union between different materials, the concentrations of mechanical stress can be reduced, increasing the life component, among others. The alloys of Al-Si10-Mg are the preferred choice of material for die-casting applications, this is due to the properties with which silicon (Si) contributes, among them, the increase of the fluidity, decrease of the shrinkage of In addition, solidification increases the corrosion resistance as the Si content increases. The role of magnesium (Mg) in Al-Si alloys provides the property of making them bondable and achieving considerably higher strength and hardness values, in addition to improving machinability. The manufacture of Al-Si10-Mg alloys by additive manufacturing is a powder bed process, where a laser or electron beam traces the pattern of the part in a layer of fine powder and a new layer of powder is deposited on the previous. The beam traces the pattern of the second layer, and joins the melted zones of the two layers. The process continues until the part is finished. EXPERIMENTAL METHODOLOGY In this work AlSi10Mg aluminum alloys were manufactured by additive manufacturing in the form of 1*1*2 cm cubes with a "SLM 280 HL solutions GmbH" equipment and evaluated by electrochemical tests. The samples were placed with copper wire to make the electrical connection, roughed with # 600 silicon carbide sandpaper and dried with ethanol before the electrochemical tests. The electrochemical techniques used were Electrochemical Noise (RE) and Linear Polarization Resistance (RPL) in electrolytes of distilled water (H2O) and sodium chloride (NaCl) at 3.5% by weight. RESULTS The time series in potential and current in H2O showed an unstable corrosion potential during the 120 hrs of exposure and the transients decrease their amplitude as the exposure increases. In the current time series, the transients moved away from the average at the beginning of the exposure and subsequently decrease. The time series in potential and current in the NaCl solution, it was observed that transients in potential tend to decrease in their amplitude by increasing the exposure time. The corrosion current density tended to increase when the exposure in the electrolyte increased and the transients did not move away from the mean. The RPL results in distilled water presented similar corrosion velocity values in the different immersion times, without showing a linear increase in their values; while for the NaCl solution average values of approx. 0.04 mm / year. CONCLUSIONS In the graphs of electrochemical noise and polarization curve, a pitting corrosion mechanism is identified in the distilled H2O solution, while in the NaCl solution pitting at a greater depth is observed. The alloy AlSi10Mg in NaCl tends to present corrosion in the thermally affected area by the fusion laser.

Corrosion behaviour of Ti–Ni–Al alloys in a simulated human body solution

The effect of Al additions (5, 10, 15 and 20at.%) on the corrosion behaviour of a 50at.% Ti–50Ni alloy in Hank solution has been investigated by using potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), electrochemical noise (EN) and linear polarization resistance (LPR) measurements. Microstructure evolution was observed from columnar grains to equiaxed grains in samples with low and high Al additions, respectively. All the different techniques indicated that with the addition of either 5 or 10at.% Al not only decreases the uniform corrosion rate, but also the susceptibility to pitting corrosion. EIS technique has shown that the corrosion resistance of these alloys is due to a TiO2 layer with a duplex structure. Results have been explained in terms of the difference in microstructures for the different alloys.

Corrosion Behavior of Alloy 625 in Simulated Nuclear High-Level Waste Medium

The present investigation aims to study the effect of various ions present in nuclear high-level waste (HLW) (acidic) medium on the corrosion resistance of Alloy 625, with solution-annealed and sensitized microstructure. The heat-affected zones are prone to sensitization during welding of components and subsequent exposure to acidic waste during service could result in intergranular corrosion in these regions and hence it was attempted to study the corrosion behavior of the alloy under sensitized conditions. Double loop electrochemical potentiokinetic reactivation test was carried out to obtain the extent of chromium depletion. Potentiodynamic anodic polarization and electrochemical noise investigations were carried out on Alloy 625 in 3 M nitric acid and simulated nuclear HLW medium (prepared in 3 M nitric acid) at 298 K and 323 K. The study showed that the alloy possess good corrosion resistance in 3 M nitric acid and simulated HLW medium. However, a marginal decrease in the corrosion resistance occurred in simulated HLW when compared to the plain acid, as observed from an increase in passivation current density, decrease in transpassive potentials, and decrease in electrochemical noise resistance. Increase in temperature of the medium and change in microstructure from solution-annealed to sensitized state further decreased the corrosion resistance of Alloy 625. Electrochemical noise time records obtained at open circuit conditions showed a stable passive film for 22 h of immersion of the alloy in 3 M nitric acid and simulated HLW. However, the amplitude of current fluctuations was higher for the sensitized microstructure when compared to the solution-annealed microstructure.