Galvanic Corrosion Resistance Research Articles

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.

A method for preparing alloy coating on the aluminum alloy substrate via laser cladding technology to prevent the galvanic corrosion of TC4/5083 couple

The Cu-Ni-Cr alloy coating was prepared on 5083 aluminum alloy substrate using laser cladding technology. The microstructure of the coating and its galvanic corrosion resistance in contact with TC4 alloy were studied. The results indicate that the Cu-Ni-Cr alloy coating primarily consists of Al-rich dendrite phase and Cu-rich matrix phase. The shear strength of the Cu-Ni-Cr alloy coating is 154.68 MPa, which is greater than that of the aluminum alloy substrate. The galvanic current density of the TC4/Cu-Ni-Cr couple is 0.05 μA·cm−2. The neutral salt spray corrosion test results demonstrate that the Cu-Ni-Cr alloy coating exhibits excellent resistance to galvanic corrosion. The coating can attenuate the galvanic corrosion effect when it is in contact with the TC4 titanium alloy, offering new solutions to address the galvanic corrosion challenges between titanium alloy and aluminum alloy in marine environments.

TiC morphology and corrosion resistance of CrMnFeCoNi+x(TiC) coatings prepared by laser cladding

The corrosion resistance of CrMnFeCoNi coatings with varying TiC contents and the evolution of TiC within these coatings were comprehensively investigated. These CrMnFeCoNi coatings, with different TiC concentrations, were fabricated using laser cladding technology. The behavior of TiC evolution in CrMnFeCoNi coatings was observed to follow a distinct pattern. At a TiC loading of 2 wt%, TiC exhibited a dispersed distribution. Interestingly, in coatings loaded with 4 wt% TiC, TiC was observed in various shapes, including elongated, square, petaled, and circular forms owing to the melting of TiC particles under the influence of a high-energy laser beam. The convection action of the molten pool combined several unmelted, partially melted, and precipitated TiC particles, resulting in diverse shapes. Furthermore, increasing the TiC content to 10 wt% led to the aggregation and fusion of TiC into clusters. Additionally, the electrochemical corrosion resistance behavior of CrMnFeCoNi coatings with varying TiC content displayed a significant correlation with the TiC concentration. As the TiC content increased, the galvanic corrosion resistance also increased. At lower TiC content levels, a higher number of electrochemical cells formed between the CrMnFeCoNi matrix and the dispersed TiC, leading to an elevated corrosion rate. In contrast, as the TiC content increased, the dispersed TiC phase fused together, reducing the likelihood of electrochemical cell formation. Notably, the electrochemical corrosion resistance of the CrMnFeCoNi coating containing 10 wt% TiC resembled that of the TiC-free coating.

Effects of the TiO2 content on the mechanical properties and galvanic corrosion resistance of Al2O3 coatings

In this study, the conventional air plasma spraying (APS) technology was employed to deposit Al2O3 coatings with varying TiO2 contents (AT coatings) on a Ti80 substrate. The coating microstructure was characterized using scanning electron microscopy (SEM), as well as the mechanical properties including fracture toughness and Vickers hardness by indentation method. Besides, the galvanic corrosion behavior of a 921A/AT coating system couples was thoroughly investigated in comparison to a 921A/Ti80 couple. The influence of TiO2 content on the resistance of Al2O3 coatings to galvanic corrosion were discussed experimentally and theoretically. Microstructural observation indicated that the introduction of TiO2 into Al2O3 coating was conducive to improving coating quality, exhibiting a decreasing value in surface roughness and porosity. Besides, improved fracture toughness and decreasing hardness were observed for samples with higher contents of TiO2. Both experimental and theorical results demonstrated that the AT coatings could potentially inhibit the galvanic corrosion which occurred on 921A/Ti80 couples, but its resistance to galvanic corrosion weakened conversely with the increase of TiO2 content. Thereinto, the volume resistivity played a decisive role.

Microstructure evolution and its effect on the corrosion of dissimilar aluminum alloys friction stir welding joint

Microstructural heterogeneity in weld nugget zone (WNZ) of dissimilar AA7050-AA2024 friction stir welding joint and its effect on galvanic corrosion (GC) were explored. The increase in solid-solutioned Zn content and the number of intergranular MgZn2 greatly worsens the corrosion resistance of local AA7050-WNZ, while the grain refinement and fragmented Al2Cu slightly improves that of local AA2024-WNZ. The heterogeneous microstructure evolution lowers the GC resistance of global WNZ, causing the severest GC at WNZ-bottom with lowest resistance. The GC and intergranular corrosion synergistically promote the dissolution process. This work provides an insight on GC of dissimilar joint from microstructural heterogeneity.

Role of KMnO<sub>4</sub>–NaF Treatment in Galvanic Corrosion Resistance of AA5083 Coupled to Steel

The role of KMnO4–NaF conversion treatment in the galvanic corrosion resistance of AA5083 aluminum alloy coupled to AISI 1045 carbon steel in synthetic seawater (diluted 100 times) was investigated. The 10 min-treated AA5083 was observed to reduce the period of high current density during the early stage of coupling and decrease the number of localized corrosion damages on the AA5083. The 10 min conversion treatment significantly reduced the electrode potential of bulk Al6(Fe, Mn), and it was concluded that the Al6(Fe, Mn) particles on the conversion-treated AA5083 no longer acted as a local cathode at the electrode potential when the AA5083 was in contact with AISI 1045 carbon steel. The decrease in cathodic activity of Al6(Fe, Mn) was attributed to the removal of Fe from the surface film of Al6(Fe, Mn), addition of Mn by the conversion treatment, and thickening of the film.

Chemical Conversion Treatment of AA5083 Aluminum Alloy and AISI 1045 Carbon Steel under Galvanically Coupled Condition in Na<sub>2</sub>MoO<sub>4</sub>: Effect of pH on Corrosion Resistance

To ascertain the effect of solution pH of Na2MoO4 chemical conversion treatment for aluminum/steel joints on corrosion resistance, AA5083 aluminum alloy and AISI 1045 carbon steel were immersed in 50 mM Na2MoO4 at pH ranges of 8–12 under galvanically coupled condition. Subsequently, in diluted synthetic seawater, the galvanic corrosion resistance of the AA5083 alloy connected to the AISI 1045 carbon steel was assessed. The number of localized corrosion damages was counted, and AA5083 treated at pH 11 was found to be the better corrosion resistance. The oxygen reduction current on bulk Al6(Fe, Mn) decreased with increasing solution pH of the conversion treatment. The Al6(Fe, Mn) particles on AA5083 were not preferential cathodes, and alkalization through oxygen reduction would not occur when the treatment was performed above pH 9. Auger electron spectroscopy analysis showed that Mo-accumulation, Fe-removal, and film thickening occurred on the particles of AA5083 treated at pH 11. These factors contributed to the suppression of the cathodic activity of the Al6(Fe, Mn) particles, resulting in the improved galvanic corrosion resistance of AA5083.

The improved galvanic corrosion resistance of a eutectic high entropy alloy through heat treatment

The improved galvanic corrosion resistance of a eutectic high entropy alloy through heat treatment

Friction stir spot welding and its weld-bond of aluminum alloy and CFRP

In this study, the possibility of using adhesive for friction stir spot welding was investigated with the aim of improving the strength and rigidity of aluminum and CFRP dissimilar material joining members and improving galvanic corrosion resistance. As a result, it was found that there is a trade-off relationship between the friction stir spot welding, which improves the joint strength in proportion to the frictional heat, and the weld bond, in which the adhesive is thermally decomposed by the frictional heat. When using adhesive together, it is necessary to consider the selection of adhesive and the optimization of frictional heat according to the application and required strength level.

Galvanic Corrosion of AA5083/Fe in Diluted Synthetic Seawater: Effect of Anodizing on Local Electrochemistry on and around Al 6 (Fe,Mn) on Al-Matrix

In 100-times diluted synthetic seawater at 298 K (pH 8.2), the effect of anodizing on the galvanic corrosion resistance of AA5083 coupled to pure Fe, Type 430, or 304 stainless steel was investigated by measuring the galvanic current densities and electrode potentials. Anodizing in H 2 SO 4 effectively suppressed the galvanic corrosion of AA5083. It was shown that an increase in pitting potential by anodizing alone could not determine whether galvanic corrosion would occur or not. The cathodic activity on Al 6 (Fe, Mn), which causes alkalization on and around Al 6 (Fe, Mn) particles, decreased as the anodizing time and voltage increased. And, the anodic oxide film on the Al-matrix in alkaline environments became stable as the thickness of the oxide film increased. A comparison of these two factors revealed that the dissolution resistance of surface oxide film on Al-matrix contributed the galvanic corrosion prevention of anodized AA5083 coupled to pure Fe. In the case of AA5083 anodized at 16 V for 180 s, no galvanic corrosion damage was observed on the AA5083 coupled to Type 430 or 304.

Study on aramid short fiber reinforced CFRP/aluminum layered structure and its galvanic corrosion resistance

In order to strengthen the bonding interface and weaken the influence of galvanic corrosion on carbon fiber/aluminum laminated composite, the aramid fiber with resin was introduced into the bonding layer of carbon fiber aluminum laminated composite structure to composite in this study. The ultimate load of carbon fiber/aluminum laminated composite reinforced by aramid fiber was studied based on the End Notched Flexure (ENF) three-point bending test and the fracture surface was analyzed and compared by Scanning Electron Microscopy (SEM) observations. Compared with the pure resin adhesive, the bearing capacity of Carbon Fiber Reinforced Polymer (CFRP)/aluminum composite structure reinforced by thin film prepared by 1 mm aramid short fiber can be increased by 9.7%. After the accelerated corrosion test, the bearing capacity of 1 mm aramid fiber film has been reduced by only 8.40% compared with the structure without corrosion treatment. However, compared with the CFRP/aluminum composite structure with pure resin adhesive layer, the ultimate bearing capacity of the specimen with aramid fiber reinforced adhesive layer is still 28.69% higher after immersion in salt solution corrosion environment. The aramid fiber reinforced carbon fiber/aluminum galvanic corrosion protection mechanism of the layered composite structure was discussed with detailed Scanning Electron Microscopy (SEM) observations and the Energy Dispersive Spectroscopy (EDS) spectrum analysis of corrosion product elements.

Improvement in Galvanic Corrosion Resistance between AA5083 and Pure Fe or Stainless Steels in Diluted Synthetic Seawater Due to Anodizing

Because of worldwide emission gas control, the weight reduction for automobiles has been widely required. Multi-material structures for automobiles, in which several materials like steels and aluminum alloys are utilized, are effective methods as techniques to reduce the weight; however, the galvanic corrosion becomes a serious problem for the joints between steels and aluminum alloys. In our previous research [1], galvanic corrosion damages on pure aluminum coupled to pure iron or stainless steel were prevented by anodizing because the anodic oxide film on pure aluminum becomes thicker with increasing anodizing time and voltage. For aluminum alloys, intermetallic particles on aluminum alloys become the initiation sites of localized corrosion; therefore, anodizing behavior on intermetallic particles should be important for preventing the galvanic corrosion damage on aluminum alloys. In this research, anodizing conditions were determined to prevent the localized corrosion generation on AA5083 when pure iron or stainless steels were coupled to AA5083. Pure iron, type 304 stainless steel, type 430 stainless steel, and AA5083 (Al-Mg alloy) were prepared as specimens in this research. Diluted synthetic seawater (200 mg/L Cl-, pH 8.2) was used as the electrolyte for electrochemical measurements. The electrode area was ca. 10 mm2. Ag/AgCl (3.33 M KCl) was used as the reference electrode. Galvanic currents and electrode potentials of aluminum alloy electrode were measured via a zero resistance ammeter. The distance between steel and aluminum alloy electrodes was kept at 10 mm. Additionally, anodizing was treated to AA5083 in various anodizing voltage and time conditions. The galvanic currents and electrode potentials of AA5083 coupled to pure iron were measured. The galvanic currents were anodic currents during the measurements, and the small oscillations of galvanic currents and electrode potentials were generated. After the measurements, many pits and filiform corrosion were observed on AA5083. The localized corrosion was induced by ennoblement of the electrode potentials of AA5083.[1] Takumi Kosaba, Izumi Muto, Yu Sugawara: Effect of anodizing on galvanic corrosion resistance of Al coupled to Fe or type 430 stainless steel in diluted synthetic seawater, Corros. Sci., 179 (2021), 109145.

Investigation of crevice corrosion of metallic fastened joints in carbon fiber reinforced polymer (CFRP) exposed to coastal seawater

Purpose The purpose of this paper is to study the susceptibility of these three commonly used corrosion resistance fasteners in seawater. For a more practical scenario, a local Atlantic coastal seawater as received was used. Design/methodology/approach Carbon fiber reinforced polymer (CFRP) was fabricated with T700 carbon fiber (Toray Inc.) and VE8084 vinyl ester resin (Ashland) to make a unidirectional composite panel of thickness 1.8 mm. A conductive paint was applied to one of the sample edges that was perpendicular to the fiber direction, providing an electrical contact with carbon fibers to connect a copper wire. This external electric connection was used for potential measurements of both the open circuit potential (OCP) of the CFRP sample, and the mixed potential of the fastened set: consisting of the CFRP and the metallic fastener fastened to it. Three common fastener alloys were selected: 316SS, Monel and Titanium. For this purpose, a high impedance voltmeter was used in conjunction with a saturated calomel reference electrode. Measurements were taken daily. For longer time measurements, a four-channel high impedance analog data logger was used with 30 min sampling rate. Findings For both 316SS and Monel fastened sets, crevice corrosion occurred inside the occluded regions of the set, when immersed in coastal seawater. The attack was more severe for 316 stainless steel set. An isolated island attack of faceted surfaces morphology was seen for 316SS set. While, a circular ring of preferential grain boundary attack appeared for Monel set, indicating an IR (voltage) drop mechanism is more likely operating. Titanium-fastened sets showed high resistance to crevice corrosion when simmered in seawater. However, for long-time exposure, the sets became more susceptible to crevice corrosion attack supported by CFRP attachment (oxygen reduction reaction taking place at the carbon fibers). Originality/value Evidently, titanium, stainless steels and Monel are good candidates for galvanic corrosion resistance. However, their susceptibility to crevice corrosion when coupled with CFRP is a new challenging topic that needs further investigation. This is very important today because the vast application witnessed for CFRP material. This work involves developing an original methodology for this kind of investigation and was done at advanced laboratories of SeaTech at Florida Atlantic University by the Atlantic coastline.

Corrosion Behavior and Galvanic Corrosion Resistance of WC and Cr3C2 Cermet Coatings in Madeira River Water

Thermally sprayed cermet coatings are adequate solutions to improve cavitation and wear resistance of hydraulic turbines made of stainless steel (SS), especially in rivers with a high sediment load, such as the Madeira River in Brazil. However, some cermets are easily dissolved in river water, leading to premature failure of the coating and costly maintenance. Moreover, galvanic corrosion induced by coupling the cermet to a SS can accelerate the coating dissolution. Therefore, the corrosion resistance of six cermets (WC-12Co, WC-10Ni, WC-10Co-4Cr, Cr3C2-25NiCr, Cr3C2-10NiCr and Cr3C2-10Ni) and the galvanic corrosion resistance of these materials coupled to CA6NM SS were evaluated in a solution that simulated Madeira River water. WC-12Co and WC-10Ni cermets exhibited the highest corrosion rates, 0.077 and 0.068 mm/year, respectively, whereas the Cr content in the WC-10Co-4Cr (0.017 mm/year) and Cr3C2-based coatings (0.005 to 0.007 mm/year) led them to corrode at slower rates. Moreover, the WC-10Co-4Cr and Cr3C2-based cermets exhibited negligible galvanic corrosion current when coupled to the CA6NM SS, making them good options to coat hydraulic turbines. In contrast, WC-12Co and WC-10Ni coatings underwent a more severe galvanic corrosion process, which would drastically reduce the lifespan of these materials as hydraulic turbine coatings.

Galvanic Corrosion Behavior between Aluminum and Iron in Chloride Solutions at Near-Neutral pH and Corrosion Prevention By Anodizing

The joints between steels and aluminum alloys are expected to be used as multi-material structures due to their low cost, high stiffness, and high corrosion resistance. When aluminum alloys are connected to steels, galvanic corrosion is expected to occur because the corrosion potentials of aluminum alloys are lower than those of iron and steels. In the case of the galvanic corrosion in chloride solutions at near-neutral pH, the anodic reaction on aluminum alloys are oxide film formation and/or pitting. For pure Al and aluminum alloys, the generation of localized corrosion is evaluated by the critical potential for localized corrosion, such as pitting potential. In this study, the electrode potential under galvanic coupling and pitting potential were compared. Surface modification is effective methods for improvement on corrosion resistance of aluminum alloys. However, there is little research related to the galvanic corrosion between steels and aluminum alloys. In this research, the galvanic corrosion behavior of pure aluminum coupled to pure iron in chloride containing near-neutral pH solutions and the effect of anodizing on galvanic corrosion were investigated.Pure iron and pure aluminum were prepared as specimens in this research. The specimen surface of aluminum was polished down to 0.25 µm with a diamond paste. The iron surface was also polished down to 1 µm with a diamond paste. Diluted synthetic seawater (200 mg/L Cl-, pH 8.2) was used as the electrolyte for electrochemical measurements. The electrode area was ca. 10 mm2. Ag/AgCl (3.33 M KCl) was used as the reference electrode. Galvanic currents and electrode potentials were measured. The distance between iron and aluminum electrodes was kept at 10 mm. A zero resistance ammeter was used to measure the galvanic currents. The electrode potential of pure aluminum was also measured. Additionally, anodizing in sulfuric acid was conducted to pure aluminum in various voltages and times. Galvanic current measurements were carried out between these anodized specimens and pure iron to evaluate the effect of anodizing on galvanic corrosion prevention.The galvanic currents and electrode potentials of pure aluminum coupled to pure iron were measured. The galvanic currents were anodic currents. The oscillations of galvanic currents and electrode potentials were generated during the measurements. Filiform corrosion was observed on pure aluminum after the measurements. The generation of filiform corrosion was caused by higher electrode potentials of pure aluminum coupled to pure iron compared with the initiate potential for filiform corrosion.The time variation of galvanic currents and electrode potentials of anodized aluminum coupled to pure iron were also measured in the diluted synthetic seawater (pH 8.2). Pure aluminum specimens were anodized at 4, 8 and 16 V at 18 s. The oscillations were observed in the galvanic currents of anodized aluminum (4 and 8V); however, no oscillation was measured on the specimen anodized at 16 V. After the measurements, pitting was observed on anodized aluminum (4 and 8V). However, no pitting was observed on the specimen anodized at 16 V. The thickness of anodic oxide film was measured. It was confirmed that the thickness of the oxide film increased with anodizing voltage. Consequently, it was indicated that the galvanic corrosion resistance of pure aluminum for galvanic corrosion was enhanced by the increase of the thickness of the oxide film.

Effect of anodizing on galvanic corrosion resistance of Al coupled to Fe or type 430 stainless steel in diluted synthetic seawater

In 100-times diluted synthetic seawater at 298 K (pH 8.2), the effect of anodizing on the galvanic corrosion resistance of Al coupled to Fe or Type 430 stainless steel was investigated by measuring the galvanic current densities and electrode potentials of the Al. The optimal anodizing conditions for the corrosion prevention of Al/Fe and Al/Type 430 were determined. The results of this study clearly indicate that the increase in the initiation potential of localized corrosion due to anodizing in H2SO4 effectively prevents the atmospheric corrosion of Al coupled to steels.

Enhancement of resistance to galvanic corrosion of ZE41 Mg alloy by equal channel angular pressing

AbstractThe galvanic corrosion behavior of as‐received and ECAPed ZE41 Mg alloy coupled with Al7075 alloy is investigated using zero resistance ammeter in three different corrosive environments, 0, 0.1, and 1 M NaCl, to mimic the conditions experienced in engineering applications. The mechanism of galvanic corrosion for the ZE41 Mg–Al7075 aluminum alloy is explained. It is observed that a robust surface film containing a composite layer of oxide/hydroxide of magnesium and aluminum is established in deionized water (0 M). However, only a single layer of magnesium oxide/hydroxide is detected in chloride‐containing environments. Equal channel angular pressing (ECAP) improved the resistance to galvanic corrosion by 58% and 54% when compared with the as‐cast counterparts in 0 and 1 M NaCl solution, respectively. In contrast, galvanic corrosion resistance decreased by 26% in 0.1 M NaCl after ECAP while the as‐received samples evinced pits unfavorable to be used in engineering applications. ECAP is a promising method to combat galvanic corrosion encountered by ZE41 magnesium alloy used in automobiles and components of military vehicles.

Galvanic Corrosion Behaviour of Phosphate Nodular Cast Iron in Different Types of Residual Waters and Couplings

The aim of this paper is to analyze the corrosion process that occurs in galvanic couplings of different alloys. The study focuses on materials that can come into contact in submersible pumps used by water treatment plants. Because, the rotor, one of the pump main components must possess high chemical and mechanical properties, nodular cast iron is usually used. Therefore, this is exposed in the same environment with different types of materials, such as aluminum, copper, bronze, grey cast iron, low alloy steel or stainless steel from which other components are made. The tests have been performed in three types of residual waters with neutral, acidic and basic pH. According to this study, the nodular cast iron galvanic corrosion resistance is highly improved by the phosphate layer deposited on its surface.

Galvanic Corrosion Behaviour of Phosphate Nodular Cast Iron in Different Types of Residual Waters and Couplings

The aim of this paper is to analyze the corrosion process that occurs in galvanic couplings of different alloys. The study focuses on materials that can come into contact in submersible pumps used by water treatment plants. Because, the rotor, one of the pump main components must possess high chemical and mechanical properties, nodular cast iron is usually used. Therefore, this is exposed in the same environment with different types of materials, such as aluminum, copper, bronze, grey cast iron, low alloy steel or stainless steel from which other components are made. The tests have been performed in three types of residual waters with neutral, acidic and basic pH. According to this study, the nodular cast iron galvanic corrosion resistance is highly improved by the phosphate layer deposited on its surface. Keywords: galvanic corrosion, wastewater, nodular cast iron, phosphate layer, galvanic couple

Effect of Ti interlayer on corrosion behavior of nanostructured Ti/TiN multilayer coating deposited on TiAl6V4

To improve the corrosion properties of TiAl6V4 alloy, TiN monolayer and Ti/TiN multilayer coatings are deposited by reactive magnetron sputtering. The phase, structure, and morphology properties are investigated by grazing‐incidence X‐ray diffraction, field‐emission scanning electron microscopy, and atomic force microscopy, respectively, and the corrosion behavior is evaluated by electrochemical impedance spectroscopy and potentiodynamic polarization. The TiN monolayer and Ti/TiN multilayer with thickness of 1,350 and 1,410 nm have the (111) and (002) preferred orientation and crystallite size of 42.5 and 24.3 nm, respectively. Columnar growth in TiN is hindered by the Ti interlayers and no cracking is observed between the layers indicating strong adhesion. The nanostructured Ti/TiN coating forms stable surface titanium oxide which improves the corrosion resistance by approximately 80 and four times compared with TiAl6V4 alloy and TiN coating, respectively. Hindrance of the columnar structure in TiN by the Ti interlayer decreases the local corrosion rate and enhances the galvanic corrosion resistance by forming a layer on the β‐phase enriched with vanadium as well as a TiO2 stable layer. The nanostructured Ti/TiN coating demonstrates capacitive behavior with phase angles approximately −50° and high impedance values at low frequency to be the corrosion resistance mechanism.