Potentiodynamic Tests Research Articles

Influence of the oxidizing technique on the biocompatible and corrosion properties of Ti6Al4V in a physiological environment

This work aims to evaluate the corrosion and biocompatibility properties of oxide films generated on Ti6Al4V alloys using both traditional and novel methods. Oxide films were generated by anodization and plasma treatment to achieve a blue surface finish. The oxide films were then characterized and compared to a native film formed on the Ti6Al4V.Electrochemical tests, incorporating potentiodynamic tests and electrochemical impedance spectroscopy, were employed to define the electrochemical resistance of oxides in an environment simulating biological exposure. In vitro tests were conducted to study ion release and biocompatible properties over a 6-week period of exposure to a 0.9 wt% NaCl solution, at body temperature. Various spectroscopic techniques, including ToF-SIMS, XRD, and Raman analysis, were used to study the structure and chemistry of the oxide films. The sub-surface layer was analysed by microstructural investigation.The type of oxidation was found to have a key influence on the oxide composition, especially with respect to the depth distribution of the individual alloy elements through the oxide film. The oxidation process determines which of the alloying elements are released into the environment, as a result of the corrosion reactions.

Optimizing biomimetic hydroxyapatite coating on Ti-6Al-6Mo alloy: influence of immersion time

This study investigates the formation and characteristics of hydroxyapatite (HAp) coating on Ti-6Al-6Mo alloy through immersion in a supersaturated calcification solution (SCS) for 3, 7, and 14 days. X-ray diffraction (XRD) and secondary electron microscopy (SEM) with electron dispersive spectroscopy (EDS) were used to identify the phases and characterize the morphology and composition of the HAp layer. Atomic force microscopy (AFM) and contact angle tests were used to evaluate the surface properties, while potentiodynamic corrosion testing in Hanks’ solution was used to assess corrosion behavior. It is confirmed that the sample immersed for 14 days formed an HAp layer on the Ti-6Al-6Mo substrate with a Ca/P ratio of 2.5, approaching the ideal value of 1.67. This HAp film exhibits a smooth and homogeneous crystal structure, with a surface roughness of 31.47 nm and an appreciable corrosion rate of 0.0005 mm y−1. This study signifies the impact of immersion time on the microstructural properties and biocompatibility of biomimetic HAp coatings applied to Ti-6Al-6Mo alloy, contributing to the progress of HAp coatings in biomedical engineering.

Comparative Study for Corrosion Resistance of Ferrous and Non-ferrous Pipes Immersed in Magnetized Water

This study aims to investigate the corrosion resistance of galvanized steel (GS) and AZ31 pipe materials immersed in a magnetized water treatment (MWT) applied river water source. The potentiodynamic corrosion test results showed that a better corrosion rate is obtained by the AZ31(corr.rate: 0.0442 mm/y) specimen than GS (corr.rate: 0.0764 mm/y) due to the passivation efficiency resulting from the calcite and MgO particles on the surface.

The influence of pH electrolyte on the electrochemical deposition and properties of cerium oxide thin films

Thin cerium oxide layers cathodically deposited on zinc were studied. These electrochemically deposited coatings provide effective corrosion protection and require less deposition time compared to chemical conversion coatings. The kinetics of their formation depend on various factors, such as temperature, applied current density, electrolyte composition, pH, and agitation. In this study, the effect of bath solution pH was investigated, with coatings produced at room temperature from aqueous cerium nitrate solutions. Chronopotentiometry, linear sweep voltammetry, and electrochemical impedance spectroscopy (EIS) were used to monitor the deposition process, while scanning electron microscopy and energy-dispersive spectroscopy were performed to characterize the deposits. Corrosion resistance was evaluated through potentiodynamic tests in a 3.5% NaCl solution. The results indicate that the electrolyte pH significantly influences the cerium electrodeposition process. Based on the findings, the cerium oxide coating obtained from a pH 4 solution exhibited lower corrosion current density, higher polarization resistance, and superior anti-corrosion performance.

Corrosion protection investigations of oxide‐silane composite coating on hot dip aluminized steel

AbstractThe hot dip aluminized ASTM 1035 steels (Al‐coated steel) underwent anodic oxidization, and various thicknesses of Al2O3 coating were applied to the surface of the Al‐coated steels (Al–Al2O3‐coated steel). The corrosion resistance of the Al–Al2O3‐coated steel was investigated using potentiodynamic tests, electrochemical impedance spectroscopy tests and measurement of galvanic current density in a bimetallic cell. It was found that the anodic oxidation resulted in the formation of a porous Al2O3 coating on the surface of the Al‐coated steel, improving both its corrosion resistance and galvanic corrosion resistance when coupled with carbon fiber reinforced nylon 6 composite (Cf/PA6). Silane treatment effectively sealed the pores within the Al2O3 coating, resulting in improved corrosion protection for Al–Al2O3‐coated steel due to the exceptional insulation, impermeability and hydrophobic properties of silane coating. Compared to the Al‐coated steel/carbon fiber reinforced polymer (CFRP) couple and Al–Al2O3‐coated steel/CFRP couple, stable galvanic current density decreased by approximately 75% and 45%, respectively.

Atmospheric Plasma Treatment to Improve PHB Coatings on 316L Stainless Steel.

In the present study, biopolymeric coatings of polyhydroxybutyrate (PHB) were deposited on 316L stainless steel substrates. The PHB coatings were developed using the spin coating method. To improve the adhesion of the PHB coating on the substrate, this method uses an atmospheric plasma treatment. Adhesion tests show a 156% increase in adhesion after 5 s of surface treatment. Raman spectroscopy analysis of the polymer shows the incorporation of functional groups and the formation of new hydrogen bonds, which can help us bind drugs and promote osteogenesis after plasma treatment. Additionally, the electrochemical behaviors in artificial body fluids (Hanks' solution) of the PHB coatings on the steel were evaluated with potentiodynamic tests, which revealed a decrease in the corrosion current and resistance to the transfer of the charge from the electrolyte to the 316L steel because of the PHB coating. All the PHB coatings were characterized using scanning electron microscopy and Raman spectroscopy after the electrochemical tests. This analysis confirmed the diffusion of electrolyte species toward the surface and the degradation of the polymer chain for the first 15 s of treatment with atmospheric plasma. These findings support the claim that plasma surface modification is a quick, environmentally friendly, and cost-effective method to enhance the performance of PHB coatings on 316L stainless steel for medical devices.

Investigation of bio-corrosion behavior, structural and thermal properties of Ni20Ti50Sn30 high-temperature shape memory alloy

In this study, Ni20Ti50Sn30 (atomic %) sample was prepared using the arc melting method. Some thermodynamic parameters (phase transformation temperatures, PTT; enthalpy, ΔH; and phase transformation hysteresis, H) obtained from the phase transformations of the alloy were determined using differential scanning calorimetry (DSC). The sample exhibited high-temperature shape memory alloy (HTSMA) properties. X-ray (XRD) analysis was performed to determine the crystal structure properties at the alloy. The presence of B2, B19′, Ti2Ni, β-Ti, Ni3Sn4, TiNiSn and Ti3Sn phases was identified through X-ray analysis of the alloy. Scanning electron microscopy (SEM) was used to examine the pre- and post-corrosion surface morphologies of the sample, with EDX analysis being performed to reveal chemical structure determinations (matrix phases, precipitates and weathering zones). The presence of dendritic arms was observed, while martensite plates were absent in all SEM images. Particularly in the SEM image taken after corrosion, it was noted that the TiO2 layer placed on the surface of the matrix rich in Ti elements altered the surface morphology of the alloy. The presence of Ti and O elements in the post-corrosion EDX analysis confirmed the existence of this layer. Biocompatibility studies of the alloy were conducted using potentiodynamic corrosion tests and electrochemical impedance spectroscopy (EIS) methods. It was determined that the NiTiSn sample was in the excellent stability class according to corrosion standards.

Influence of Process Parameters on the Mechanical Properties and Corrosion Resistance of Dissimilar Friction Stir Welded Joints of AA2024-O and AA6061-O Aluminum Alloys

The influence of the process parameters, traverse, and rotational speeds of dissimilar friction stir welded joints of AA2024-O and AA6061-O aluminum alloys on the corrosion resistance was evaluated. Potentiodynamic tests using a 3.5% NaCl solution, open circuit potential, and polarization curves showed the corrosion behavior for the different welding parameters. These data were correlated with those obtained by mechanical tests (microhardness, tensile, and fracture analysis) and microstructure analysis by optical and scanning electron microscopy. It was observed that the combined effect of the parameters influenced the variation of corrosion resistance. This was evidenced mainly by the improvement of corrosion resistance at 1200 rpm–65 mm·min−1, which was related to the tendency of grain size and heat input presented. The corrosive attacks on the welded joints presented greater affectations in the presence of base material 1 (AA6061-O) with higher metallic dissolution. Corrosion attacks abovementioned were presented in different forms, such as pitting, localized, and selective, and they were observed by scanning electron microscopy. Finally, in corrosive and mechanical terms, the best performing condition was 1200 rpm and 65 mm·min−1 compared to the low parameter of 840 rpm and 45 mm·min−1.

Improvement of corrosion resistance and electrical conductivity of a Cr–C coated heat-assisted forming stainless steel bipolar plate for proton exchange membrane fuel cell

Heat-assisted forming is gaining increasing attention for its potential in improving the formability and quality of metallic bipolar plate (BPP) of proton exchange membrane fuel cell (PEMFC). However, the effects of heat-assisted forming and the subsequent coating process on corrosion resistance and electrical conductivity of stainless steel BPP still remain unclear. This work proposes a way to improve simultaneously the corrosion resistance and electrical conductivity of heat-assisted forming stainless steel BPP by depositing a Cr–C coating directly on its surface without removing the oxide layer using the magnetron sputtering method. Potentiodynamic tests indicate that self-corrosion current density and corrosion current density at 1.0 V (vs. Ag/AgCl) of the Cr–C coated heat-assisted forming SS316L BPP prepared under 900 °C for 10 min are 0.021–0.040 μA cm−2 and 77.54 μA cm−2, respectively, both of which are smaller than those of coated SS316L BPP formed under room temperature. In addition, the contact resistance is close to that of the gold-plated copper plate under the same pressure. The corrosion resistant intermediate oxide layer and conductive network formed between Cr–C coating and metal substrate through defects of oxide layer may be the main reason for improvement of its corrosion resistance and electrical conductivity, respectively.

Copper-Decorated Titanium Electrodes: Impact of Surface Modifications of Substrate on the Morphology and Electrochemical Performance.

This study investigates the effect of surface modifications of the titanium substrate on the growth of electrochemically deposited copper. These materials are intended to serve as cathodes in the electroreduction of nitrates in aqueous solutions. Surface modifications included the use of hydrogen fluoride for titanium etching and anodization to promote the growth of a structured titania nanotube array. The effect of an intermediate calcination step for the nanotubes before deposition was assessed along with a comparison to an untreated substrate electrode. The materials were comprehensively characterized by SEM, XRD, contact angle, potentiodynamic tests, EIS, and cyclic voltammetry. Their electrocatalytic ability was tested in the reduction of aqueous solutions containing nitrates. The results reveal that surface finishing impacted the shape and size of the Cu microparticles, as well as the nucleation mechanism enabling a crystal-facet-controllable synthesis. All the materials exhibited microsized copper particles with a spherical shape with some clusters. On the etched titanium surface, a high number of heterogeneous submicroscopic particles were also present. The thermally treated anodized substrate promoted the development of a combination of sparse microparticles corresponding to defect sites in amorphous titanium and the presence of a diffuse coating of octahedral nanosized particles whose growth was promoted by the tetragonal structure of anatase crystals. Electrochemical tests display reduced charge transfer resistance upon copper deposition on the modified substrates, which is indicative of the enhanced conductivity of the coated materials. Additionally, cyclic voltammetry and electrolysis experiments reveal the electrodes' potential for nitrate reduction, showing a better response for the etched titanium substrate (30% nitrate removal, after 2 h at 25 mA cm-2).

Effect of magnetron sputtering C-doped CrN film on the conductivity and corrosion resistance of 304 stainless steel bipolar plates

Using a high-power impulse and direct current (DC) magnetron sputtering approach, C-doped CrN films with various C-target pulse frequencies are created on the surface of SS 304. The microstructure, corrosion resistance and conductivity of the films are examined. With the decreases of C-target pulse frequency, the roughness of the CrCN films decreases and the density increases. The results of XPS and TEM analyses demonstrate that C atoms are either present in CrN lattice as interstitial atoms or precipitate at grain boundaries to form amorphous carbon, which facilitates the increase of film density and conductivity. In the potentiodynamic tests, the CrCN-1000 Hz film exhibits the lowest corrosion current density 0.54 μA/cm2 at 0.6 V vs. Ag/AgCl potential. The values of icorr and Ecorr are 0.11 μA/cm2 and 0.427 V, respectively. Furthermore, the CrCN-1000 Hz film has the lowest interface contact resistance (ICR) under a compaction force of 140 N/cm2 after potentiostatic polarization test, indicating that C doping is beneficial to improve the corrosion resistance and conductivity of CrN film.

Evaluation of microstructure, corrosion resistance performance, and mechanical properties of 316L austenitic stainless steel FCAW welded joints: a comparative study

ABSTRACT This research aims to not only examine the effect of different mixtures of Ar and CO2 on microstructural features and corrosion behavior of double-pass FCAW of 316L SS but also compare these characteristics with gas tungsten arc welding (GTAW) and self-shielded FCAW. Different shielding gas mixtures, namely 100%Ar, 100%CO2, 82%Ar+18%CO2 were used to make the specimens. All specimens represent biphasic microstructures containing austenite (Ɣ) and delta-ferrite (δ-ferrite). Based on the potentiodynamic (PD) test results, the anti-corrosion protection performance of the welded region was enhanced when using GTAW compared to self-shielded FCAW. Additionally, the impedance value of the GTAW joint was higher than that of the FCAW-welded specimens. The ductility of welded joints was ranked as GTAW > CO2 +Ar shielded FCAW > self-shielded FCAW > CO2 shielded FCAW. The ranking of transverse tensile strength was as follows: CO2 shielded FCAW> self-shielded FCAW > CO2+ Ar shielded FCAW> GTAW.

Comparative study of metallic foil friction stir welded and conventional friction stir welded AZ61 Mg alloy butt joints: Biomedical and engineering applications

Metallic Foil Friction Stir Welding (MFFSW) was newly developed from the Friction Stir Welding (FSW) technique. Magnesium (Mg) alloys were the most trending alloys in the aerospace, automobile, and biomedical industries. This study aims to investigate the variation in mechanical, corrosive, microstructural, and fractographic properties of MFFSW as a process innovation when compared with FSW. The metallic foil of pure manganese (Mn) with a thickness of 500 μm was inserted between two AZ61 Mg alloys. The tensile strength, impact strength, and hardness were noted as mechanical properties of the output. Potentiodynamic corrosion tests were performed to reveal the corrosion properties. An optical microscope was used to examine a distinct transverse section of the weld. Fractography tests with scanning electron microscopic analysis were conducted on destructive tensile specimens. The ultimate tensile strength, impact energy, yield strength, and microhardness increased to 16%, 32%, 12%, and 19.17%, respectively, compared to FSW. MMFSW shows a lower elongation of up to 33% than FSW. MMFSW (9.61 mm/A) shows a lower corrosion rate than FSW (11.02 mm/A), which employs improved corrosion properties. Optical microscopy images of the stir zone in both MFFSW and FSW revealed that adding a Mn alloying element improved grain growth uniformity and eliminated unexpected grain growth patterns. Hence, the experiment’s conclusion shows that MFFSW has the edge over FSW for mechanical and corrosion properties. Thus, the Mn strip improves the properties of MFFSW.

Influence of Hybrid Surface Modification on Biocompatibility and Physicochemical Properties of Ti-6Al-4V ELI Titanium.

Titanium-based materials are the most widely used materials in biomedical applications. However, according to literature findings, the degradation products of titanium have been associated with potential allergic reactions, inflammation, and bone resorption. The corrosion process of Ti-6Al-4V in the human body environment may be exacerbated by factors such as reduced pH levels and elevated concentrations of chloride compounds. Coatings made of biopolymers are gaining attention as they offer numerous advantages for enhancing implant functionality, including improved biocompatibility, bioactivity, wettability, drug release, and antibacterial activity. This study analyzes the physicochemical and electrochemical behavior of the Ti-6Al-4V ELI alloy subjected to PCL and PCL/TiO2 deposition by the electrospinning method. To characterize the polymer-based layer, tests of chemical and phase composition, as well as surface morphology investigations, were performed. Wetting angle tests were conducted as part of assessing the physicochemical properties. The samples were subjected to corrosion behavior analysis, which included open circuit potential measurements, potentiodynamic tests, and the electrochemical impedance spectroscopy method. Additionally, the quantification of released ions post the potentiodynamic test was carried out using the inductively coupled plasma atomic emission spectrometry (ICP-AES) method. Cytotoxicity tests were also performed. It was found that surface modification by depositing a polymer-based layer on the titanium substrate material using the electrospinning method provides improved corrosion behavior, and the samples exhibit non-toxic properties.

Laser powder bed fusion of pure copper electrodes

This study explores the fabrication and characterization of a pure copper electrode for an EDM equipment using laser powder bed fusion (LPBF) and comparing its performance with an original cast sample. The microstructural, mechanical, electrical, thermal, and corrosion characteristics of the samples were analyzed. The microstructure of the additively manufactured (AM) sample exhibited superior mechanical properties, with an 18 % increase in ultimate tensile strength and more than two times greater elongation in comparison with those of the cast sample. Moreover, the electrical and thermal conductivity coefficients of the AM sample were found to be consistent with industry standards as 5.52 × 107 S/m and 361 W/mK, respectively. Additionally, the potentiodynamic polarization corrosion test results of the AM sample further exhibited superior corrosion resistance in terms of the corrosion potential particularly in a 3.5 % NaCl environment. Advanced electron microscopy techniques were used to investigate the differences in the properties of the AM and cast samples and further shed light on the superior properties of the LPBF counterpart. Despite challenges in manufacturing pure copper components through LPBF, this study demonstrates the feasibility of producing a functional part that competes effectively with cast counterparts and excels in certain aspects.

Effect of Flame Remelting on the Microstructure, Wear and Corrosion Resistance of HVOF Sprayed NiCrBSi Coatings

As a post treatment, thermal remelting is an effective method to eliminate pores and establish a metallurgical bonding for thermal sprayed coatings. However, it is rather difficult to obtain simultaneously high corrosion and wear resistance, since additional energy input usually leads to more homogeneous microstructure in coatings, which deteriorates mechanical hardness. In this work, flame remelting has been imposed to high velocity oxygen-fuel sprayed self-flux NiCrBSi coatings. The remelting effects on microstructure were characterized in terms of porosity and phase analysis. The microhardness, wear resistance and corrosive behaviors were compared among substrate steel, as-sprayed and as-remelted coatings. Results show that the lamellar boundaries and internal defects in the as-sprayed coatings have been eliminated by remelting. The coating porosity has substantially reduced from 7.36% to 0.75%, and a metallurgical bonding at the coating/substrate interface has been formed. Comparing with the as-sprayed coatings, the microhardness of the remelted coatings increases about 21% and the wear weight loss reduces about 42%. By flame remelting, the wear mechanism changes from furrow and abrasive wear to micro-cutting and local fracture. The remelted coatings have also exhibited better corrosion resistance by means of salt spraying and potentiodynamic tests.

Investigations on surface properties of friction stir welded dissimilar AA2024-T3 and 304 stainless steel joints

The present study investigated the influence of tool rotational speed on dissimilar joints between AA2024-T3 and SS304 metals using friction stir welding (FSW). Optimal results were achieved at 560 rpm tool rotation, 25 mm/min traverse speed, and 1 mm tool pin offset. This rotation rate facilitated proper heat input, inducing plastic deformation and material flow, resulting in an ultrafine grain structure in the stir zone (SZ). 3D profilometry showed variable surface roughness affected by process parameters. Potentiodynamic tests demonstrated improved corrosion resistance in FSWed samples compared to the base material. Vickers hardness testing revealed increased hardness in the SZ due to grain refinement. Wear behavior evaluation highlighted the significant influence of tool rotation on enhancing wear resistance in welded specimens.

Electrochemical performance of metal nitride coated titanium bipolar plate for proton exchange membrane water electrolyser

In order to improve corrosion resistance and electric conductivity of titanium bipolar plate (BPP) for proton exchange membrane water electrolyser (PEMWE), three different metal nitride (i.e.Ta/TaN, Cr/CrN and Nb/NbN) coated titanium bipolar plates are prepared by magnetron sputtering. The coated BPP is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscope (AFM), and their electrochemical performance is assessed by electrochemical corrosion tests including open circuit voltage (OCP), potentiodynamic and potentiostatic polarization tests in the simulated PEMWE anode environment. It is revealed that the surface roughness of titanium substrates is decreased after coating, implicating the reduced interfacial contact resistance (ICR). Potentiodynamic and potentiostatic tests demonstrate that Ta/TaN and Nb/NbN coatings can significantly improve the corrosion resistance of titanium bipolar plate. The corrosion current density of coated substrate is reduced by approximately 67 % upon coating with Ta/TaN and Nb/NbN under the simulated PEMWE anode environment. However, the ICR of Ta/TaN coating is the lowest (3.9 mΩ × cm2), which is reduced by 74 % compared with pristine titanium substrate (14.9 mΩ × cm2). Hence, the Ta/TaN coated BPP is tested in single electrolytic cell and demonstrates significantly improved electrolysis efficiency.

Protection of N80 steel from erosion-corrosion of geothermal water by nanoparticle-modified expoxy resin coatings

In order to investigate the erosion-corrosion resistance of nano-SiO2/EP composite coating and TiO2/EP composite coating in a geothermal environment, the coatings were subjected to potentiodynamic polarization curve tests, AC impedance tests, weightlessness tests, under different immersion time in geothermal water. The micro-morphology of the coating after erosion-corrosion was observed to evaluate the protective effect of the modified EP coating on N80 steel. The result showed that the addition of nanoparticles can improve the corrosion resistance of EP coatings to a certain extent, and the optimum addition amount of nanoparticles is 3%. In geothermal water containing sand, the corrosion inhibition efficiency of EP coatings modified by nanoparticles was above 99.99% except for the 1 wt% SiO2/EP composite coating. When the nanoparticle content is 1 wt%, the protective effect of nano-SiO2/EP composite coating is better than that of TiO2/EP composite coating, but the protective effect is opposite when the nanoparticle content is 3% and 5%, respectively.

CORROSION RESISTANCE OF COLD-ROLLED AISI 301 STAINLESS STEEL

: The performed investigations concerned on the effect of cold rolling on the corrosion behavior and microstructure of austenitic AISI 301 stainless steel. Samples of steel strip were cold-rolled within the degree of deformation 30%, 50% and 80%. The corrosion resistance test was examined using gravimetric and potentiodynamic method. Corrosion tests were conducted in acidic and alkaline corrosive environments. A light microscope and a scanning electron microscope were used to observe the surface morphology of the samples after corrosion testing. Corrosion tests by gravimetric method showed that investigated steel is not resistant to corrosion in 0.5N H2SO4 solution, while no significant weight loss was observed in artificial seawater solution (0.5N NaCl). Based on potentiodynamic tests carried out in 0.5N NaCl solution, it was found that the pitting corrosion resistance of the tested cold-rolled steel AISI 301 decreases with an increase in the degree of plastic deformation in the range of 30% to 80%. However, a decrease in the corrosion potential and an increase in the current density were observed on the polarisation curves. The propensity of the steel to initiation and propagation pitting was found to increase both with increasing degree of deformation and the associated increase in the volume proportion of martensite- in the material structure. The occurring of martensite- ’ in the investigated steel was confirmed by X-ray methods.