Electrochemical Test Methods Research Articles

An Electrochemical Approach to Accelerate Mechanically Assisted Crevice Corrosion Damage on Modular Implant Interfaces

Abstract Corrosion within the crevice of modular tapers is one of the major mechanisms that leads to orthopedic device failures. However, the currently used fretting corrosion test methods involve extended test durations and are often burdensome. This study evaluates the feasibility of adding micromotion to crevices while being simultaneously subjected to cyclic polarization in order to accelerate corrosion damage. The addition of micromotion was intended to induce crevice and fretting corrosion between metals in a washer-rod combination geometry. Three commonly used orthopedic metals (316L stainless steel, SS316L; grade 5 titanium, Ti6Al4V; and cobalt-chromium-molybdenum per ASTM F1537-20, Standard Specification for Wrought Cobalt-28Chromium-6Molybdenum Alloys for Surgical Implants [UNS R31537, UNS R31538, and UNS R31539], CoCrMo) were used to form crevices in this study to evaluate the test method. A cyclic polarization control group in which no micromotion was present was used to determine the effect of the cyclic polarization alone. In addition, a fretting control group in which no cyclic polarization was conducted was used to assess the effect of micromotion without cyclic polarization. The results of this study showed that fretting corrosion damage can be achieved on Ti6Al4V and SS316L washer crevices when subjected to micromotion alone. The test method did not induce more corrosion on Ti6Al4V samples when crevices were tested with cyclic polarization alone. Furthermore, the results found that cyclic polarization in combination with micromotion did not achieve the same fretting corrosion damage on the CoCrMo samples as observed in explants. Still, electrochemical test methods have potential for accelerating corrosion damage within crevices when combined with existing fretting corrosion testing and therefore could potentially reduce test durations for fretting corrosion susceptibility evaluations for medical devices having modular taper connections.

Construction of superhydrophobic film on the titanium alloy welded joint and its corrosion resistance study

PurposeThis study aims to improve the corrosion resistance of TA2-welded joints by superhydrophobic surface modification using micro-arc oxidation technology and low surface energy substance modification.Design/methodology/approachThe microstructure and chemical state of the superhydrophobic film layer were analyzed using scanning electron microscopy, energy dispersive X-ray spectroscopy, three-dimensional morphology, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared absorption spectroscopy. The influence of the superhydrophobic film layer on the corrosion resistance of TA2-welded joints was investigated using classical electrochemical testing methods.FindingsThe characterization results showed that the super hydrophobic TiO2 ceramic membrane was successfully constructed on the surface of the TA2-welded joint, and the construction of the super hydrophobic film greatly improved the corrosion resistance of the TA2-welded joint.Originality/valueThe superhydrophobic TiO2 ceramic membrane has excellent corrosion resistance. The micro nanostructure in the superhydrophobic film can intercept air to form an air layer to prevent the corrosion medium from contacting the surface, thus, improving the corrosion resistance of the sample.

Investigating the Corrosive Influence of Chloride Ions on Slag Recovery Machine Shells in Power Plants.

An effective strategy for achieving cost-effective and environmentally friendly desulfurization wastewater in coal-fired power plants involves the incorporation of desulfurization wastewater into the slag water system. The objective of this study was to analyze the corrosion behavior of Q235-A slag-picker shell material upon the introduction of FGD wastewater into the slag water system. The dynamic weight loss method, electrochemical testing method and microscopic phase characterization were employed to investigate the impact of varying chloride ion concentrations (ranging from 1000 mg/L to 30,000 mg/L) of flue gas desulfurization wastewater (FGD wastewater) on the corrosion of Q235-A slag-picker shell material. The test results indicate that as the concentration of chloride ions increases, the corrosion rate increases from 1.1487 mm/a to 1.5590 mm/a when the concentration is less than 10,000 mg/L. However, when the concentration exceeds 10,000 mg/L, the corrosion rate decreases from 1.559 mm/a to 1.0393 mm/a. The corrosion rate is above 1 mm/a at all concentrations. As the Cl- concentration, the quality of the corrosion product film initially increases and then decreases. The primary components of the corrosion product are α- FeOOH, γ-FeOOH, β-FeOOH, Fe3O4 and γ-Fe2O3.

The Effect of Temperature on Electrochemical Corrosion Behavior of HDR Duplex Stainless Steel

To study the effect of temperature on the electrochemical corrosion behavior of HDR duplex stainless steel, the corrosion resistance of HDR at different temperatures was investigated using the electrochemical test method and combined with metallographic microstructure observation and the EDS analysis based on the characteristic that the metal structure determines. The results show that the HDR contains inclusions such as silicide and nitride, mainly distributed in the ferrite phase and its boundary. The pitting of HDR occurs when the polarization potential of -0.5–1.5 V is applied at different temperatures ranging from 10 °C to 80 °C. The pitting occurs mainly in the ferrite and its boundary below 50 °C and in the austenite and ferrite tissues above 60 °C. Cl−, inclusions, and Cr oxides are the important factors affecting corrosion. The corrosion rate of HDR increases with the increase in temperature; the higher the temperature is, the more serious the corrosion is. The critical pitting temperature of HDR is between 50 °C and 60 °C. The pitting potential below 50 °C is above 0.65 V, while that above 60 °C is below 0.60 V.

How to Choose Suitable Reference Electrode and Aqueous Electrolyte to Avoid Error in Electrochemical Measurements?

Objective: To reduce the experimental error, three commonly used reference electrodes (Hg/HgO, Hg/Hg2Cl2 (SCE), and Ag/AgCl) are investigated to select the appropriate electrode in different aqueous electrolytes. Methods: Besides, the correct electrochemical test method is proposed according to the stability of the reference electrode. After measuring the potential difference of reference electrode in various aqueous electrolytes, it is found that Hg/HgO electrode is suitable for alkaline electrolytes, with minimum deviation in 6 M KOH solution, SCE should be used in acidic electrolytes, with minimum deviation in H2SO4 solution less than 1 M, and both SCE and Ag/AgCl electrode can be used in neutral electrolytes. Results: Due to the liquid junction potential, the result of using the double salt bridge is more accurate than that of using the single salt bridge. Conclusion: The stability of various reference electrodes in electrolytes is discrepant. Therefore, calibration is emphasized since the potential of the reference electrode drifts and even becomes invalid after prolonged use.

Investigation of the regeneration of the passive surface oxide layer of TiAl6V4 alloy printed by WAAM technology using different electrochemical test methods

AbstractThe kinetics of oxide layer formation on surface of Ti6Al4V alloy samples is a very important property especially if their application as medical implants is planned. Damaged protective surface layer usually heals in ambient condition however; during the self‐healing process toxic species can get into the surrounding living tissue. In our experiment the kinetics of the healing process proceeding at 3D printed alloy surface has been studied using electrochemical methods, among them scanning electrochemical microscopy. More than 40 min. time period was found long enough for total healing.

Comparison study of corrosion behavior for chitosan coated Ti6Al4V alloy produced by selective laser melting and forging

In recent years, the selective laser melting (SLM) technique has attracted widespread interest due to its ability to prepare biomedical materials with complex geometries, high dimensional accuracy and cost-effectiveness. However, Ti6Al4V alloy produced by SLM technique is faced with poor corrosion resistance and bio-inertness problems. Therefore, in this study, chitosan coatings were performed on Ti6Al4V alloy produced by electrophoretic deposition (EPD) forging (traditional method) and SLM for 15 min and 30 min. Corrosion behaviors of chitosan coated surfaces were compared by using electrochemical corrosion test method in simulated body fluid (SBF). The highest corrosion potential (Ecorr) values were −504 mV for forged and −592 mV for SLM on chitosan coated surfaces for 30 min. As a result, the chitosan coating showed that the Ti6Al4V alloy produced by the SLM technique increased the corrosion resistance. When the deposition time was 30 min, the resulting chitosan coating was about 1.4 order of magnitude than the untreated sample for the Ecorr value for both sample groups. Therefore, thanks to the biocompatible chitosan coating obtained by the EPD technique, the corrosion resistance of the surfaces produced using SLM has reached a level that can compete with forged surfaces.

Developing levodopa-modified sol-gel coating with enhanced anticorrosion performance on Mg alloy AZ31

PurposeThis study aims to develop a sol-gel-based coating to provide a long-lasting corrosion protection on AZ31 Mg alloy. Silane-based sol-gel coatings have been successfully applied to Mg alloys for corrosion protection. However, the micro or nano defects formed during condensation and solidification will cause the coating failure during a long-lasting immersion in a saline solution. More durable corrosion-protective sol-gel coatings are needed.Design/methodology/approachA sol-gel-based coating was modified on AZ31 Mg alloy by levodopa (DOPA). The long-lasting corrosion protection mechanism was studied by multiple electrochemical testing methods and surface characterization techniques.FindingsLong-term testing by electrochemical impedance spectroscopy in aqueous 0.1 M NaCl indicated that the modified DOPA@sol-gel coating exhibited significant corrosion protection performance (>14 days). In comparison, the DOPA-free sol-gel coating failed only after three days of testing. The improved corrosion protection is attributed to the self-polymerized DOPA filling to the micro or nano defects in the glassy cross-linked networks of the sol-gel coating, which greatly improves the compactness of the coating.Originality/valueThe method of this study is simple and easy to process, the raw materials are green and the protective effect is excellent, which is of significance for the study of magnesium alloy corrosion protection.

Study on corrosion resistance mechanisms of gradient-structured austenitic stainless steel materials based on passivation behavior

SMAT treatment produced gradient-structured deformation layers of a certain thickness, and the gradient structure and residual stresses were then characterized using SEM and XRD. A layer-by-layer electrochemical test method was created and employed to study the impact of the gradient structure on the passivated film and the corrosion resistance mechanism of the deformed layers at various depths. The findings demonstrate that when depth is increased, both residual stresses and grain size decrease. The layer-by-layer experiments reveal that residual compressive stress and grain size reduction work together to produce a passivation film with fewer flaws and more stability, as indicated by MS. This is primarily attributable to grain size reduction's increased number of nucleation sites in the passivation film and the residual compressive stress acting as a driving force for passivation film growth.

Multi-scale analysis for accelerated degradation mechanisms of cylindrical LiFePO4/graphite batteries under distinct positions of jelly roll

Lithium iron phosphate (LFP) batteries are widely used in the electric vehicle due to the great chemical stability and cost advantages. Fluctuations in the environment and driving conditions lead to a deterioration in battery performance that is inevitable. In addition, due to the winding manufacturing characteristics of cylindrical battery electrodes, the uneven distribution of current and temperature accelerates the aging process. In this paper, the cross-comparison aging test of cylindrical LFP batteries is designed, in which three kinds of constant current and two different dynamic working conditions are used for accelerated aging test at high temperature. The aging behavior and mechanism are investigated quantitatively by combination of in-situ electrochemical test and ex-situ Post-Mortem methods. During the long-term cycle of the battery, external characteristic parameters such as capacity, internal resistance, and open circuit voltage are periodically checked up. Until the capacity retention falls below 80%, the batteries are disassembled to sample the electrodes at the specified positions from the jelly roll. The material morphology changes of electrodes are observed by scanning electron microscopy. The half-cell tests were produced to obtain material-level aging information based on performance tests. This multi-scale analytical method enables the detailed process of performance loss, which guides performance prediction and safety diagnostics.

Anti-corrosive non-aqueous DBSA/MEA lamellar liquid crystal lubrication system

HypothesisSince lamellar liquid crystals (LLCS) could be used for lubrication, many LLCS systems have been constructed to improve lubrication performance. However, most studies focused on the LLCS of the water system, and its corrosiveness brought some limitations to its application. Therefore, it is necessary to construct a non-aqueous LLCS system with good lubrication and anti-corrosion properties to improve its applicability. ExperimentsAnionic surfactant dodecyl benzene sulfonic acid (DBSA) was used to construct non-aqueous LLCS in different solvents, including monoethanolamine (MEA) and diethanolamine (DEA). DBSA/H2O LLCS system was constructed for comparison. The LLCS was characterized by polarizing microscope (POM), small-angle X-ray scattering (SAXS), and rheology. Its microstructure was discussed. Meanwhile, we evaluated the lubrication and anti-corrosion performance of LLCS. Its lubrication mechanism was explained through tribology tests and X-ray photoelectron spectrometer (XPS) analysis of the wear scar surface. Its anti-corrosion mechanism was investigated by using the weightlessness method, electrochemical test method, and quantum chemical theoretical calculations. FindingsThe DBSA/MEA non-aqueous LLCS system showed better lubrication performance than DBSA/DEA and DBSA/H2O LLCS. It can adsorb on the surface of the friction pair to form a lubrication friction film, which plays a better role in reducing friction and wear. The DBSA/MEA LLCS is less corrosive to metals because it can effectively isolate oxygen and water in the air between friction pairs. Furthermore, the lone pair electrons in the 2p orbital of the N atom in the MEA molecule could coordinate with the 3d empty orbital of the Fe atom, forming a protective film on the metal surface, which plays a good anti-corrosion effect. This work not only enriched the study of non-aqueous LLCS but also expanded its potential applications in the field of lubrication.

Study on corrosion behavior of Ni–P/Ni–Cu–P superhydrophobic composite coatings preparation on L360 steel by two-step method

The two-step process of electroless plating and electrodeposition was used to successfully prepare a bilayer composite film by electroplating a Ni–Cu–P film with hydrophobic properties on the Ni–P film. The histological features of the two membrane layers were compared. The L360 pipeline steel, Ni–P coating and Ni–Cu–P composite film were evaluated by electrochemical test and erosion corrosion method. Under simulated seawater conditions, the material properties changed before and after different periods of service. The experimental results show that the introduction of Cu can inhibit the growth of cellular structures on the surface of the coating, increase the number of nucleation points, and improve the microstructure of the coating during the deposition of Ni–Cu–P films. The Ni–P/Ni–Cu–P bilayer composite film has a pinecone-like convex structure, which can greatly reduce the surface energy of the film layer and endow the film layer with hydrophobicity. At the same time, it effectively resists the adsorption of water and other external impurities on its surface, and has good anti-fouling performance, thereby slowing down the surface corrosion and improving corrosion resistance. In addition, copper enables the composite coating to have passivation and a uniform and dense coating structure, which is the main reason for the improvement of the corrosion protection performance of the composite coating. The protective effect of the coating can effectively improve the electrochemical resistance and erosion resistance of L360. The Ni–P/Ni–Cu–P bilayer composite film reduces the electrochemical corrosion rate of the substrate from 0.417mmpY to 0.025mmpY, and the scouring weight loss rate of the film decreases to 0.05% of the substrate.

Analysis of corrosion inhibition of Kleinhovia hospita plant extract aided by quantification of hydrogen evolution using a GLCM/SVM method

During a corrosion inhibition test, a combination of common electrochemical corrosion test methods with an in-situ quantification of H2 evolution could provide a comprehensive analysis of the effectiveness of an organic inhibitor. This work analyzes the corrosion inhibition efficiency of Kleinhovia hospita plant extract on carbon steel specimens polarized in 1 M HCl, based on acquired H2 bubbles images, by using gray level co-occurrence matrix (GLCM) and support vector machine (SVM) classification. A conformity was established between the classified-algorithm models and the corrosion test results obtained by potentiodynamic polarization test and electrochemical impedance spectroscopy. Hydrogen rate and corrosion rate show the same lowest trends at the addition of 3000 mg/L of KH extract. The inhibitor addition led to 99% of maximum inhibition efficiency. Based on the polarization data, KH extract is a mixed type inhibitor. Supported by Langmuir calculation for adsorption isotherm, a physisorption is stated as the main inhibition mechanism. The feature extraction using GLCM was able to distinguish changes in H2 bubbles characteristics where the addition of inhibitor affected the corrosion rate. The GLCM/SVM method applied as a linear kernel function and showed 88% accuracy with d = 5 for image data testing. Remarkable changes in H2 gas bubbles characteristic were observed in the specimen immersed in the solution with 3000 mg/L inhibitor addition, signified by 99% inhibition efficiency.

Revealing the Selective Bifunctional Electrocatalytic Sites via In Situ Irradiated X-Ray Photoelectron Spectroscopy for Lithium-Sulfur Battery.

The electrocatalysts are widely applied in lithium-sulfur (Li-S) batteries to selectively accelerate the redox kinetics behavior of Li2 S, in which bifunctional active sites are established, thereby improving the electrochemical performance of the battery. Considering that the Li-S battery is a complex closed "black box" system, the internal redox reaction routes and active sites cannot be directly observed and monitored especially due to the distribution of potential active-site structures and their dynamic reconstruction. Empirical evidence demonstrates that traditional electrochemical test methods and theoretical calculations only probe the net result of multi-factors on an average and whole scale. Herein, based on the amorphous TiO2- x @Ni selective bifunctional model catalyst, these limitations are overcome by developing a system that couples the light field and in situ irradiated X-ray photoelectron spectroscopy to synergistically convert the "black box" battery into a "see-through" battery for direct observation of the charge transportation, thus revealing that amorphous TiO2- x and Ni nanoparticle as the oxidation and reduction sites selectively promote the decomposition and nucleation of Li2 S, respectively. This work provides a universal method to achieve a deeper mechanistic understanding of bidirectional sulfur electrochemistry.

Effects of the corrosion mechanism evolution of low silicon-cast aluminium alloys in service

ABSTRACT The corrosion mechanism evolution of four low silicon-cast aluminium alloys exposed to heat treatment at 200°C for 0–50 h was studied by means of immersion corrosion, intergranular corrosion and electrochemical test, SEM, EDS and EBSD analysis methods. The correlation of corrosion resistance with composition and the thermal exposure time was investigated. The results show that the corrosion mechanism of all aluminium alloys changed after thermal exposure at 200°C. Before thermal exposure, intergranular corrosion was the main corrosion, and after 200°C thermal exposure, serious pitting corrosion and spalling corrosion occurred in the local area. The contents of Si and Mg in the grain boundary increased obviously. The contents of elements in the poor zone of the grain boundary increased, and the electrical potential difference between the grain and the grain boundary reduced. The intergranular corrosion sensitivity of the alloy was reduced. But the degree of pitting gradually becomes serious. The electrochemical test of the aluminium alloy with 3.5 wt% Si showed that its corrosion potential increased with the increase inthermal exposure time, and its corrosion current density increased with the increase inthermal exposure time. After the EBSD test, it was found that the large angle grain boundary decreased gradually and the proportion of large grain size increased with the increase in thermal exposure time to 50 h.

A sensing platform based on Cu-MOF encapsulated Dawson-type polyoxometalate crystal material for electrochemical detection of xanthine

A promising sensing platform based on polyoxometalate-based metal-organic framework (POMOF) was established for sensitive electrochemical detection of xanthine (XA). In the unique structure of POMOF, the Dawson polyoxoanions P2W18 were encapsulated into 3D open copper-mixed ligand nanotube framework Cu-MOF, in which the cavity of the metal-organic framework provides a specific shelter to prevent the aggregation and loss of polyoxometalate in electrocatalytic reactions; meanwhile, unsaturated Cu(II) active sites of Cu-MOF can also serve as electrocatalytic active center. The POMOF-based sensor (CuMOFP2W18/XC-72R) was fabricated by using acetylene black (XC-72R) as a support material to enhance the conductivity of POMOF. The performances of the POMOF-based sensor were studied by using different electrochemical testing methods. The composite displayed remarkable electrocatalytic activity for the oxidation of XA due to the synergistic effect of polyoxometalate (POM) and metal-organic framework (MOF). The electrochemical sensor demonstrated a wide linear range (0.5μM-240μM), low detection limit (0.26μM), and excellent selectivity for detecting XA. Furthermore, the composite further demonstrated excellent reproducibility and great stability. More importantly, the proposed sensor was utilized to detect XA in real samples, which may provide a new way for early disease diagnosis.

An Investigation of the Reaction Mechanism of the Direct Electrochemical Propylene Oxidation to Propylene Oxide with Electrochemical Mass Spectroscopy

Propylene oxide is a high-value precursor in the chemical industry with a large variety of applications and a market growing 4-5% annually. Currently, more than 10% of the propylene is used for the production of propylene oxide. The traditional methods for producing propylene oxide are chlorohydrin and hydroperoxide methods. These methods are costly, environmentally pollutant, and inefficient with a high proportion of by-products[1]. Renewable energy sourced direct electrocatalytic propylene oxidation to propylene oxide stands out as a way to replace the traditional methods and overcome the mentioned disadvantages. However, there has been a very limited number of studies about this topic in the last few decades starting from the 1960s. The experimental systems in these studies were significantly different from each other in terms of electrochemical cells and test methods, temperature, reactants, catalysts, etc[2–7]. Additionally, due to the limitation of available characterization and product detection methods the conclusions could not be well established. The majority of the performed studies suffered from difficulties in detecting and accurately quantifying propylene oxide due to its high volatility and hydrolysis to propylene glycol. Likewise, recent results from Winiwarter et al. revealed that there is propylene glycol formation on Pd catalysts at high potentials above 1.0 V vs. RHE in 0.1 M HClO4 and the selectivity towards dehydrogenation products decreases however, due to the lack of sensitive and fast product analysis method they could not quantify the propylene oxide even though they could detect it [8]. Moreover, there is only a limited number of studies investigating the reaction mechanism for electrochemical propylene oxidation towards propylene oxide. The theoretical study done by Li et al. proposed propylene oxide formation on PdO2(110) at 1.23 V vs RHE where the oxygen vacancies formed on the catalyst therefore they suggest that propylene reacts with lattice oxygen. Additionally, they suggest the competing reaction pathway to epoxidation as dehydrogenation of –CH3 results in acrolein, CO, and CO2[9]. Contrarily, Otsuka suggested a tentative Langmuir-Hinselwood mechanism for electrochemical propylene oxidation to propylene oxide[10]. In conclusion, the reaction mechanism for electrochemical propylene epoxidation on Pd is still not well understood. Therefore, we focused on discovering the reaction mechanism since it is crucial to design a rational catalyst. In this work, we are investigating in-situ electrocatalytic propylene oxidation to propylene oxide on different catalysts, starting from Pd. The unique electrochemical mass spectroscopy device that we are using enables in-situ detection and quantification of propylene oxide and also competing dehydrogenation pathway products acrolein and CO2 proposed by the theoretical study of Li et al.[9]. In addition to that, this device enables us to detect these products with great time resolution, so we are able to see the differences in product distribution very quickly when we change the applied potential. With these measurements, we offer an insight into the reaction pathway towards the electrochemical formation of propylene oxide and extend our investigations to other catalysts besides Pd. We believe that this study will help to understand the reaction mechanism for different catalysts leading to a great impact on rational catalyst design for electrochemical propylene oxidation to propylene oxide. [1] T.A. Nijhuis, M. Makkee, J.A. Moulijn, B.M. Weckhuysen, Ind. Eng. Chem. Res., 45, (2006), doi:10.1021/ie0513090. [2] J.O.M. Bockris, H. Wroblowa, E. Gileadi, B.J. Piersma, Trans. Faraday Soc., 61, (1965), doi:10.1039/tf9656102531. [3] T.C. Chou, J.C. Chang, Chem. Eng. Sci., 35, (1980). [4] K. Scott, C. Odouza, W. Hui, Chem. Eng. Sci., 47, (1992),doi:10.1016/0009-2509(92)87158-M. [5] V.M. Schmidt, E. Pastor, J. Electroanal. Chem., 401, (1996), doi:10.1016/0022-0728(95)04299-7. [6] H. Wise, L.L. Holbrook, J. Catal., 298, (1975). [7] G.R. Stafford, Electrochim. Acta., 32, (1987),doi:10.1016/0013-4686(87)80024-5. [8] A. Winiwarter, L. Silvioli, S.B. Scott, K. Enemark-Rasmussen, M. Sariç, D.B. Trimarco, P.C.K. Vesborg, P.G. Moses, I.E.L. Stephens, B. Seger, J. Rossmeisl, I. Chorkendorff, Energy Environ. Sci., 12, (2019), doi:10.1039/c8ee03426e. [9] H. Li, C.S. Abraham, M. Anand, A. Cao, J.K. Nørskov, J. Phys. Chem. Lett., 13, (2022), doi:10.1021/acs.jpclett.2c00257. [10] K. Otsuka, T. Ushiyama, I. Yamanaka, K. Ebitani, J. Catal., 157, (1995),doi:10.1006/jcat.1995.1310.

Suitability of electrochemical test methods for evaluating corrosion of steel in alkali-activated slag concrete

The electrochemical tests commonly used for evaluating reinforcement corrosion in Portland cement-based concrete may not be appropriate for testing alkali-activated slag (AAS) concrete due to its different pore structure and pore solution composition. In this article, corrosion behaviour of the steel bars in 12 AAS concrete mixes with different alkali concentration and modulus of sodium silicate solution was monitored by using gravimetric mass loss measurement. The results obtained from other electrochemical tests were compared to the gravimetric mass loss to determine their suitability for assessing the corrosion of steel in AAS concrete. It was found that only 7.8–28% of the mass loss was accounted for by the macrocell current for AAS concretes, indicating that this type of test underestimates the corrosion of the steel in AAS concrete. The steel bars in the AAS concretes gave a much higher negative half-cell potential value, presumably due to the influence of sulfides. In summary, it has been established that the criteria for assessing the onset and progress of corrosion of steel in Portland cement concrete are not suitable for the same purpose in the range of AAS concretes studied.

Inhibition of multi-site adsorption of polyethylene glycol during copper via-filling process

The inhibitory effect of molecular weight (Mw) of polyethylene glycol (PEG) on the through-hole filling by copper electroplating was investigated by the electrochemical testing method and energy change with DFT. The cathodic polarization, electron transfer resistance, and diffusion coefficient of PEG with different Mw and concentration were assayed by cyclic voltammetry and electrochemical impedance spectroscopy; The inhibitory effect of different PEG Mw was demonstrated and examined by cross-sectional images using OLYMPUS confocal laser microscope, and the thickness of the copper layer and TP value were important measurement standards. The adsorption behavior on copper surfaces was calculated using the first principles. As PEG Mw and concentration are increased, the best TP value and diffusion coefficient of the plating formula is gained when PEG Mw and concentration are 20000 g/mol and 250 mg/L, they are 148.56% and 2.34 × 10-7, respectively. Better adsorption energy can be obtained as the adsorption sites of PEG increases, and the adsorption energy of PEG5 is − 1.99 eV. The experimental and theoretical results show that PEG with small Mw has no inhibitory effect, and even accelerates the deposition rate of Cu2+/1+. Only when the Mw and concentration exceed 2000 g/mol and 150 mg/L, PEG can inhibit the deposition of Cu2+/1+, and the best effect of through-hole electroplating is 20000 g/mol and 250 mg/L.

Electrochemical extraction of gadolinium on Sn electrode and preparation of Sn-Gd intermetallic compounds in LiCl-KCl melts

For the development of nuclear energy, it is important to remove the fission products which hinder nuclear reactions. In this paper, Gd was extracted by an electrochemical method in LiCl-KCl molten salts. The electrochemical reactions of GdCl3 and SnCl2 are measured by a series of electrochemical means. Three kinds of Sn-Li and four Sn-Gd alloys are obtained by cyclic voltammetry and other electrochemical means. Thermodynamic and kinetic parameters of electrode processes for Gd(III) and Sn(II) ions are calculated by different electrochemical test methods. The diffusion coefficient and diffusion activation energy of the Sn(II) ion are reactions as 2.23–3.78 × 10-5 cm2 s-1 and 24.4 kJ mol-1, respectively. Thermodynamic parameters of Sn3Gd intermetallic compounds were calculated based on open circuit chronopotentiometry at different temperatures (ΔHf0(Sn3Gd)=−229.225kJmol-1 and ΔSf0(Sn3Gd)=−38.2Jmol-1K-1). Metallic Gd is extracted by potentiostatic and galvanostatic electrolysis on liquid Sn electrode in melts, respectively. According to X-ray diffraction (XRD) and scanning electron microscopy and elemental dispersive spectrometry (SEM-EDS), the products are mainly composed of the intermetallic compound Sn3Gd and Sn metal. The experimental results show that the fission element Gd can be extracted with high extraction rate by electrolysis in molten salt system.