Galvanic Coupling Research Articles

Effect of different galvanic coupling methods on the surface chemical transformation of TC4 titanium alloy

In clinical applications, titanium and its alloy implants often suffer from corrosion, wear and tear, and poor biological activity. Surface modification is critical for improving the stability and bioactivity of titanium and its alloys. Zinc phosphate chemical conversion has received increasing attention as a promising technique for biomedical applications. However, the presence of a passive oxide layer on the TC4 (Ti6Al4V) surface poses challenges for conventional chemical conversion methods. In this study, the principle of galvanic coupling was utilized to facilitate the surface chemical transformation of TC4 titanium alloy, referred to as galvanic coupling phosphate chemical conversion (GCPCC). The effects of two types of galvanic coupling and different plastic deformations on the surface chemical transformation of TC4 titanium alloy at different temperatures were mainly investigated. The results indicate that the Ti/Fe multipoint coupling formed by magnetron sputtering during chemical transformation at 70 °C significantly enhances the nucleation sites of hopeite (Zn3(PO4)2·4H2O) and accelerates the nucleation rate. Compared with line-coupled conversion coatings, multipoint coupling GCPCC coatings exhibit superior uniformity and finer microstructure, and the thickness of the laths is significantly reduced from 5 to 10 μm to less than 1 μm. Moreover, the temperature exerts a substantial influence on the formation of conversion coatings. At 70 °C, the GCPCC coating primarily comprises hopeite, while the coating resulting from chemical conversion treatment consists of both hopeite and an amorphous ZnP-like granular coating at 50 °C.

Investigating the effect of current density in ultra-fast electrolytic zinc phosphate deposition

The influence of the current density utilized during electrolytic zinc phosphate deposition on the properties of the final coatings has been investigated. The adoption of a concentrated electrolyte allows satisfactory coating properties with current densities as high as 100 mA cm−2, resulting in exceptional deposition rates. The size of the Zn3PO4 crystals was shown to decrease with the current density, which in turn affected the coatings final properties. An explanation to this finding was provided following classical nucleation theory. Samples obtained at 25 and 50 mA cm−2 featured more compact layers while samples obtained at 100 mA cm−2 were thicker but porous. Scratch test was used to assess wear resistance, which was observed to be increasing with the applied current density. The more compact layers obtained at 25 and 50 mA cm−2 provided an enhanced corrosion resistance as highlighted by potentiodynamic polarization and electrochemical impedance spectroscopy. The adoption of an electrolytic setup allowed for co-deposition of metallic Zn which can further protect the steel substrate by galvanic coupling.

Electrochemical Evaluation of Al-5 wt% Zn Metal-Rich Primer for Protection of Al-Zn-Mg-Cu Alloy in NaCl

An intact and X-scribed Al-5wt%Zn-rich primer (AlRP) without pretreatment or topcoat was evaluated for its ability to suppress potential-dependent intergranular corrosion and intergranular stress corrosion cracking of peak-aged AA7075A-T651 in NaCl salt fog and full immersion. The ability of the primer to provide sacrificial anode-based cathodic prevention of peak-aged AA7075-T651 substrate was evaluated both under the primer coating and at scratches. The AlRP evaluated consisted an epoxy-based resin embedded with spherical Al-5wt%Zn pigment particles. Performance was evaluated under full immersion in 0.6 M NaCl solution and compared to ASTM B117 salt spray exposure using two approaches. These consisted of the University of Virginia (UVA) cycle test on intact coatings and the full immersion galvanic couple testing on simulated scratched panels created when intact coatings form bimetal couples with bare AA7075-T651. Focus was placed on the ability of the AlRP to achieve a targeted intermediate galvanic couple potential near a “prevention” potential which suppresses stress corrosion crack growth, intermetallic particle corrosion as well as intergranular corrosion. The long-term (24-h) open-circuit potential (OCP) of AlRP-coated AA7075-T651 in 0.6 M NaCl indicated that the AlRP provided less than 100 mV of cathodic potential shift of the intact coating from its OCP in 0.6 M NaCl. Electrochemical cycle testing conducted at a potentiostatic hold of –0.95 VSCE demonstrates that the AlRP did not enable sacrificial anode-based cathodic protection as the coupled potential remained at the corrosion potential of bare AA7075-T651. Furthermore, the current observed throughout galvanic corrosion experiments coupling of AlRP to AA7075-T651 indicated the AlRP coating was a cathode in the bimetal galvanic couple. ASTM B117 salt spray exposure of the AlRP revealed oxidation of the AA7075-T651 substrate below the primer detected as a continually growing oxygen signal at the primer-substrate interface that did not arrest corrosion over the exposure period.

Galvanic lithotrophy, a new path to fuel bioelectrochemical processes

Galvanic coupling with a biocompatible conductive material can make accesible unexplored electron sources for bacteria.

Comparative Analysis of SPR and SPR-Bonded Joints of Hot Press Forming Steel and AA5052 under Corrosive Conditions

The increasing demand for effective joining techniques in dissimilar materials has led to the widespread use of self-piercing rivet (SPR) mechanical joints, particularly in aluminum combinations. Studies in this field aim to enhance joint strength by optimizing process conditions, including the use of SPR-bonded processes with structural adhesives. Structural adhesives in SPR-bonded processes introduce different corrosion behavior owing to galvanic corrosion caused by potential differences between sheets over time. In this study, we utilize SORPAS® simulation to optimize SPR conditions and analyze stress and deformation. A tensile shear test was performed on a hot pressforming steel/AA5052-H32 combination for SPR and SPR-bonded processes. The experimental results indicated die sticking during SPR optimization, increased tensile strength through AA5052-H32 surface cleaning in the SPR-bonded process, varying corrosion conditions, and consistent SPR-bonded strength after salt spray exposure. The difference in failure modes between the processes concerning corrosion time can be attributed to the corrosion- mitigating effect of structural adhesive within the galvanic coupling region formed by potential differences. Additionally, adhesive and rivet failure modes were observed. Moreover, adhesive failure occurred in the SPR-bonded process after shear tensile tests, characterized by a fracture between the lower AA5052-H32 interface and adhesive. Furthermore, we found a linear relationship between the remaining adhesive area and shear tensile strength.

Enhanced Chalcopyrite Dissolution in Acidic Culture Medium: The Impact of Arsenopyrite Presence

Nowadays, research on promoting the dissolution of chalcopyrite is important. As a natural symbiotic mineral of chalcopyrite, arsenopyrite will have an impact on the dissolution of chalcopyrite. This paper shows the influence of arsenopyrite on the dissolution of chalcopyrite in an acidic culture medium. The leaching results showed that adding arsenopyrite increased the leaching concentration of copper by 332 mg/L. The residues showed a decrease in sulfur through X-ray diffraction analysis (XRD) and an increase in dissolution degree through scanning electron microscope (SEM). Electrochemical experiments have shown that the rest potential of arsenopyrite is higher than that of chalcopyrite, so there is a galvanic interaction, and the impact on chalcopyrite is greater than that of arsenopyrite. The polarization curve also proves this. Under the interaction of galvanic couples, the reduction of S0 production and the enhancement of Cu2+ release can promote the dissolution of chalcopyrite. In addition, X-ray photoelectron spectrometer (XPS) analysis under the action of galvanic coupling indicates that more SO42− is generated on the surface of chalcopyrite, replacing Sn2−/S0, and SEM shows a stronger corrosion morphology. All results confirm that the electrochemical effect between arsenopyrite and chalcopyrite promotes the dissolution of chalcopyrite in the acidic culture medium.

Mitigation of Galvanic Corrosion in CFRP-Metal Couples through Addressing the Carbon Surface

Carbon-based reinforcements are widely used in composite materials for a wide range of applications including wind energy and transportation. In the later, the carbon-fiber reinforced polymers (CFRP) components are often joined together with metallic parts creating conditions for galvanic corrosion. Therefore, a deeper understanding of the electrochemical processes occurring at the carbon surfaces is crucial for developing new approaches for the corrosion protection of multi-material assemblies.In the present work, the electrochemical performance of different types of carbons, namely HOPG (Highly Ordered Pyrolytic Graphite) glassy carbon (GC), and CFRP, have been investigated in neutral NaCl solutions under cathodic polarization. At the potentials relevant to galvanic coupling to metals the CFRP surface is the most electrochemically active of the studied carbon surfaces. The ranking of the studied surfaces in terms of supporting the oxygen reduction reaction was established as follows: CFRP > GC > HOPG. It was found that the observed differences in the electrochemical responses of these materials to ORR are correlated with the proportions of edge sites present on each carbon surface [1].Under galvanic coupling conditions in multi-material structures composed of CFRP and Al alloys or Zn, significant degradation of the composite surface occurs at the carbon/electrolyte interface and due to an attack on the epoxy of the matrix phase most probably resulting from nucleophilic attack by hydroxyl and perhydroxyl ions, formed as a result of the oxygen reduction reaction on carbon fiber. The obtained results demonstrate the intense electrochemical activity of CFRP even when slightly polarized cathodically with a concomitant sharp increase in the pH above its surface. Contrary to expectations, exposure of CFRP to degradative high pH media before galvanic coupling did not provoke accelerated galvanic corrosion of the coupled metal under bulk electrolyte immersion conditions [2].The use of the corrosion inhibition approach to suppress the degradation of CFRP and reduce its cathodic activity in the galvanic couples was also demonstrated. It was found that the presence of sodium dodecyl sulphate (SDS) in the electrolyte offers a clear inhibition effect. From the results, it is concluded that SDS interacts with CFRP surface resulting in the formation of a persistent adsorbed layer. Surface analysis by scanning electron microscopy confirms mitigation of the CFRP composite degradation under impressed cathodic polarization in the presence of SDS or after prior exposure to SDS-containing solution [3].[1] S.U. Ofoegbu, M.G.S. Ferreira, H.I.S.Nogueira, M.L. Zheludkevich, Comparison of the Electrochemical Response of Carbon-Fiber-Reinforced Plastic (CFRP), Glassy Carbon, and Highly Ordered Pyrolytic Graphite (HOPG) in Near-Neutral Aqueous Chloride Media, C, 9 (2023) 7.[2] S.U. Ofoegbu, M.C. Quevedo, A.C. Bastos, M.G.S. Ferreira, M.L. Zheludkevich, Electrochemical characterization and degradation of carbon fibre reinforced polymer in quiescent near neutral chloride media, npj Materials Degradation, 6 (2022) 49.[3] S.U. Ofoegbu, K. Yasakau, S. Kallip, H.I.S.Nogueira, M.G.S. Ferreira, M.L. Zheludkevich, Modification of carbon fibre reinforced polymer (CFRP) surface with sodium dodecyl sulphate for mitigation of cathodic activity, Applied Surface Science, 478 (2019) 924-936.

Simultaneous wastewater treatment and H2 evolution using Mg-Cu galvanic coupling

Contamination-free drinking water and potential sources of green energy are two major concerns of modern society. This article aims to address these through the development of some novel processes and facile experimental setups using analytical grade metals and seawater. Here, the Mg-Cu galvanic coupling process has been successfully used for dye removal from industrial wastewater and for green H2 production. It has been observed that the electrochemical process in the presence of seawater removes ∼100 % rhodamine B, ∼91 % methyl orange and ∼72 % methyl blue dyes within 240 min through an electrochemical reaction. The rate of dye degradation can be enhanced by increasing the area of the counter electrode. The H2 evolution is simultaneously observed from both window and counter electrodes during the dye degradation process. Collected H2 from both electrodes is equivalent to the NTP H2 volume against a meagre loss of metallic Mg dissolved in seawater. In the present work, H2 is produced for the first time by removing the pollutant from wastewater without using any external energy and without hindering the rate of H2 production.

Oral Galvanism Side Effects: Comparing Alloy Ions and Galvanic Current Effects on the Mucosa-like Model.

The interaction of different dental alloys with the oral environment may cause severe side effects (e.g., burning sensation, inflammatory reactions, carcinogenesis) as a result of oral galvanism. However, the pathogenesis of side effects associated with oral galvanism is still unclear, and the effects of direct current and alloy corrosion ions are considered potentially contributing factors. Therefore, the aim of this study was to systemically compare the damaging effects of (1) galvanism as a synergistic process (direct current + corrosion ions), (2) direct current separately, and (3) corrosion ions separately on an in vitro mucosa-like model based on a cell line of immortalized human keratinocytes (HaCaTs) to reveal the factors playing a pivotal role in dental alloys side effects. For this, we chose and compared the dental alloys with the highest risk of oral galvanism: Ti64-AgPd and NiCr-AgPd. We showed that galvanic current may be the leading damaging factor in the cytotoxic processes associated with galvanic coupling of metallic intraoral appliances in the oral cavity, especially in the short-term period (28 days). However, the contribution of corrosion ions (Ni2+) to the synergistic toxicity was also shown, and quite possibly, in the long term, it could be no less dangerous.

Electrochemical investigation on localised corrosion under silica sand deposit layers of carbon steel within a bespoke test cell

The corrosion behaviour of deep pit-like features on carbon steel under silica sand deposits has been evaluated using a bespoke localised corrosion cell. Local pH and electrochemical measurements were performed, including impedance spectroscopy and galvanic coupling. The corrosion rate of X65 carbon steel at four different recession depths up to 9 mm was evaluated in the presence and absence of a ∼8 mm-thick silica dioxide deposit layer, in a carbon dioxide-saturated environment. The deposit reduced corrosion rates to approximately 1 mm·yr−1 and iron carbonate formed on the steel surface under the deposit due to an increase in local pH.

Galvanic Corrosion of Strands in Re-Grouted, Post-Tensioned Concrete Bridges

Grouted, post-tensioned (PTD) concrete systems are widely used to construct bridges, typically with an anticipated corrosion-free service life of 100+ y. However, the usage of inadequate grout materials and grouting practices in PTD concrete systems have caused unwanted air voids in ducts, leading to strand/grout/air interface, carbonation of exposed grout layer, and localized corrosion of strands (say, within about 10 y to 20 y). Re-grouting of voids as a tendon repair strategy has led to accelerated galvanic corrosion of the portion of strands at the interface between the carbonated base grout and repair grout with different chemistry, raising concerns and reluctance in re-grouting of voids in tendons. This work focused on understanding and quantifying the galvanic corrosion at the interface of carbonated base grout and repair grout in a re-grouted tendon. The theoretical analysis based on mixed potential theory estimated a galvanic current density of approximately 2 µA/cm2 and showed that the galvanic coupling can increase the corrosion current density of the prestressing steel in the base grout by about two-fold. The study on prestressed steel in simulated solutions estimated a galvanic current density of approximately 20 µA/cm2. Then, the study on prestressing steel in grouts and the analytical simulation estimated galvanic current densities around 1.5 µA/cm2 to 2 µA/cm2 at 95% external relative humidity (ERH) and 25°C. A model relating the galvanic current density in grouted systems as a function of ERH was developed, which showed an exponential increase in the galvanic corrosion with an increase in ERH. Also, a case study showed that if the tendon anchorage region experiences 95% ERH for about 20 y, sufficient strand corrosion could happen, and structural behavior can change from ductile to brittle nature, which could be a serious concern for structures in the coastal zone.

Investigating surface wear characteristics of single-crystal SiC based on metal electrochemical corrosion

Aiming at the environmental pollution of the polishing solution in chemical mechanical polishing, this study introduces a chemical mechanical polishing technique for single-crystal SiC based on metal electrochemical corrosion. The wear properties of the SiC C-surface, as influenced by different materials on grinding balls (Cu, Fe, Al, and Al2O3), and different solutions (KCl, Na2SO4, Fenton, and H2O), were examined through wear experiments to elucidate the material removal mechanisms involved. The experiments demonstrated that the most significant wear marks, with a peak cross-sectional area of 46.89 μm2, were obtained when the C-face of SiC was ground with Al-paired grinding balls in an Na2SO4 electrolyte solution. Energy dispersive spectroscopy analysis of the wear debris revealed an O elemental content of 11 %, and X-ray photoelectron spectroscopy analysis indicated the existence of SiO2 and Al2O3 oxides. Subsequently, the effects of Na2SO4 solution concentration and pH on the wear pattern of the C-surface were investigated. The largest wear cross-sectional area (approximately 50 μm2) was observed when using an Na2SO4 electrolyte solution with a concentration of 1.25 mol/L at a pH of 9 in an alkaline solution. The proposed mechanism of material removal in single-crystal SiC via metal electrochemical corrosion involves the Al metal acting as a cathode. This causes galvanic coupling corrosion, generating a corrosion current, which subsequently induces oxidation of the SiO2 oxide layer on the anode SiC surface. The oxidized layer is then mechanically removed.

Hydrogen Production Properties of Aluminum–Magnesium Alloy Presenting β-Phase Al3Mg2

In this study, aluminum–magnesium (Al-Mg) bulk porous materials were fabricated by using uniaxial hot pressing to control the porosity rate of the material over a wide range (up to 50%). The fabricated materials were analyzed by X-ray diffraction and scanning electron microscopy. The results demonstrated the appearance of intermetallic (IM) phase Al3Mg2, and its quantity increased with the applied pressure. In the context of the decline of global fossil fuel reserves, the revalorization of these materials by hydrogen (H2) production was investigated. Hydrolysis of the Al-Mg materials was carried out in a simulated seawater solution (aqueous solution of sodium chloride 35 g/L). The results showed the role of the porosity rate in the H2 production properties of the fabricated materials; the increase of porosity rate from 10% to 50% cuts the reaction time in half. Finally, the role of IM phase Al3Mg2 in H2 production was highlighted through galvanic coupling.

Corrosion behavior of AA5052 aluminum alloy in the presence of heavy metal ions in 3.5 % NaCl solution under negative pressure

Aluminum alloy heat exchange tube is attractive for the Low Temperature-Multi Effect Distillation (LT-MED) desalination device, for its low cost and excellent mechanical property. However, it is prone to galvanic coupling corrosion in presence of heavy metal ions. In this paper, the effect of Cu2+ and Fe3+ ions on the corrosion of aluminum alloy in 3.5 wt% NaCl solution under negative pressure is investigated by the weight-loss method and the electrochemical measurements. It shows that the operation pressure affects significantly the corrosion behavior of AA5052 aluminum alloy in presence of heavy metal ions. As the pressure decreases, the resistance of the aluminum alloy to corrosion increases markedly. The corrosion products formed under different operation pressure are detected by SEM, XRD analysis. It is found that the diffusion process of corrosion products from the aluminum alloy surface into the solution is prevented as the decrease of pressure, resulting in the formation of the passivation layer on the aluminum alloy surface. The decrease of pressure can effectively restrain the heavy metal ions to be adsorbed on the defects of the oxide layer and mitigate the corrosion of aluminum during the LT-MED desalination process.

Effect of Anodic Polarization on the Susceptibility of AA6111 Automotive Sheet to Stress Corrosion Cracking

AA6xxx Al-Mg-Si-Cu alloys are increasingly used to meet lightweight objectives in automotive applications given their high strength-to-weight ratio. However, their use in conjunction with steels and carbon fiber-reinforced polymers in these applications will result in galvanic coupling that may be deleterious to the Al alloy. As such, the ability of anodic polarization to induce stress corrosion cracking (SCC) in AA6xxx, an alloy typically considered SCC-resistant, is explored. In this study, fracture mechanics-based testing under full immersion in 0.6 M NaCl was used to quantify the threshold stress intensity above which SCC can occur (KTH) and stage II SCC crack growth rate (da/dtII) as a function of applied potential at and above the freely corroding potential. Under freely corroding conditions and potentials applied within the range observed for the freely corroding potential, no SCC was observed as results matched those gathered in the air (i.e., KTH was equivalent to the measured fracture toughness). When applying potentials anodic to the freely corroding potential (greater than −706 mVSCE), a decrease in KTH and an increase in da/dtII was observed. Crack growth rates measured under anodic polarizations were slowed through the reapplication of the freely corroding potential. These data imply that galvanic coupling may have the capacity to induce severe SCC in AA6111.

Effect of substrate orientations on the electrochemical and localized corrosion behavior of a quad-layer Al alloy composite

Electrochemical and localized corrosion behavior of a 4045/7072/3003 M/4045 Al alloy composite in 3.5 wt.% NaCl solution was investigated from cross-sectional and plane directions by electrochemical impedance spectroscopy, polarization curves, and high-resolution microscopic examination. Plane directions showed higher corrosion resistance than the cross-sectional surface, with almost all localized corrosion initiated from Si-containing inclusions. The cross-section showed a complex galvanic effect among the four layers, the galvanic coupling between 4045/7072 accelerated the dissolution of 7072 because 7072 served as the anode, however, the galvanic coupling between 3003 M/4045 protected 4045 from corrosion, indicating that 3003 M served as the anode.

Microstructural and electrochemical behavior of spark plasma sintered (Cu-10Zn) + Al2O3 nanocomposites

The present work deals with developing Al2O3 reinforced α-brass (Cu-10Zn) nanocomposites through spark plasma sintering and evaluated its electrochemical properties in a 3.5% NaCl aqueous solution. Microstructural analysis revealed the uniform dispersion of Al2O3 particles with inter-particle spacing ∼2.45 µm in 3 wt.% Al2O3 nanocomposites. The initiation of Al2O3 clustering and vast clustering of particles with wide particles-free-zone were observed in 6 and 9 wt.% Al2O3 nanocomposites. X-ray diffraction peaks confirm the crystallinity and incorporation of Al2O3 in the α-brass matrix. The corrosion behavior was studied by measuring the change in open-circuit potential values, electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and potentiodynamic polarization (PDP) studies in 3.5% NaCl solution. The 3 wt.% Al2O3 nanocomposites exhibited lower icorr value than the Cu-10Zn matrix and other Al2O3 reinforced nanocomposites. The EIS results confirm the surface layer enhancement and resistance to charge transfer in 3 wt.% Al2O3 nanocomposites due to their uniform distribution in the matrix. The uniformly embedded reinforcement particles abridged the prospects of galvanic coupling, which resulted in the upliftment of corrosion resistance and passivation behavior. An increase in the icorr value beyond 3 wt.% Al2O3 nanocomposites was due to the clustering of reinforced nanoparticles and vast particle-free zones and caused intergranular corrosion.

Application of Arc Thermal Spray Process in Corrosion Protection of Steels and Electromagnetic Pulse Shielding

In the present work, an overview has been discussed on the application of arc thermal spray technology. This process used in erosion, corrosion and electromagnetic pulse (EMP) shielding. The Al coating exhibits excellent corrosion properties in simulated weathering i.e., Society of Automotive Engineers (SAE) J2334 as well as 3.5 wt.% NaCl solution at long run of application. However, weathering condition possesses Cl- and CO3-- ions, which simultaneously influence in the deterioration of Al coating. Once the Zn is alloyed with Al in coating, it enhances the corrosion attributed to the formation of severe defects and galvanic coupling between Al and Zn. The stainless steel and Ti coatings have been used on the concrete surface to reduce the corrosion of waste water reservoir where Ti is exhibited more corrosion resistance due to dense and uniform morphology as well as on the surface of Ti coating during exposure in acidic solution, it forms rutile and anatase, which further provide corrosion protection. Moreover, the Zn has beneficial properties in regards of EMP shielding rather than iron and Cu plate. Zn with copper has excellent EMP shielding compared to pure Cu. As the thickness is increased, the EMP shielding properties are increased. From this review article, it is suggested to reduce the porosity of arc thermal sprayed coating using some chemical post treatment.

In-situ electrogravimetric detection of the cathodic process during the galvanic coupling between lithium and copper

In-situ electrogravimetric detection of the cathodic process during the galvanic coupling between lithium and copper

Fully printed and self-compensated bioresorbable electrochemical devices based on galvanic coupling for continuous glucose monitoring.

Real-time glucose monitoring conventionally involves non-bioresorbable semi-implantable glucose sensors, causing infection and pain during removal. Despite bioresorbable electronics serves as excellent alternatives, the bioresorbable sensor dissolves in aqueous environments with interferential biomolecules. Here, the theories to achieve stable electrode potential and accurate electrochemical detection using bioresorbable materials have been proposed, resulting in a fully printed bioresorbable electrochemical device. The adverse effect caused by material degradation has been overcome by a molybdenum-tungsten reference electrode that offers stable potential through galvanic-coupling and self-compensation modules. In vitro and in vivo glucose monitoring has been conducted for 7 and 5 days, respectively, followed by full degradation within 2 months. The device offers a glucose detection range of 0 to 25 millimolars and a sensitivity of 0.2458 microamperes per millimolar with anti-interference capability and biocompatibility, indicating the possibility of mass manufacturing high-performance bioresorbable electrochemical devices using printing and low-temperature water-sintering techniques. The mechanisms may be implemented developing more comprehensive bioresorbable sensors for chronic diseases.