Galvanic Corrosion Potential Research Articles

Water quality assessment of Bheemasandra Lake, South India: A blend of water quality indices, multivariate data mining techniques, and GIS.

An integrated approach combining water quality indices (WQIs), multivariate data mining, and geographic information system (GIS) was employed to examine the water quality of Bheemasandra Lake, located adjacent to a sewage treatment plant (STP) in Tumakuru city, India. The analysis of 22 lake water samples, examined before and after the monsoons, revealed that the physicochemical parameters namely - electrical conductivity, biochemical oxygen demand, turbidity, total dissolved solids, ammoniacal nitrogen, nitrates, phosphates, magnesium, total hardness, total alkalinity, and calcium - exceeded the acceptable limits stipulated by national and international standards. The Canadian Council of Ministers of the Environment WQI (pre-monsoon: 25.3; post-monsoon: 33.9) and weighted arithmetic WQI (pre-monsoon: 3398; post-monsoon: 2093) designated the water as unsafe for drinking. Irrigation WQIs (sodium adsorption ratio, sodium percentage, residual sodium carbonate, magnesium hazard, permeability index, and potential salinity) implied water's suitability for irrigation. However, electrical conductivity indicated otherwise. Industrial WQIs (Larson-Skold Index, Langelier Index, Aggressive Index, and Puckorius Scaling Index) illustrated scaling propensity and the chloride sulfate mass ratio alluded galvanic corrosion potential. Hierarchical cluster analysis gathered 22 sampling points into two clusters (cluster 1: relatively lower polluted regions; cluster 2: highly polluted regions) for each season based on similarities in water features. Principal component analysis extracted four (79.07% cumulative variance) and six (87.14% cumulative variance) principal components before and after the monsoons, respectively. These components identified the primary pollution sources as urban sewage and natural lithological processes. WQI maps, created using the inverse distance weighted interpolation technique, enhanced the visualization of spatial-temporal variations. This study highlights the dire consequences of urbanization, STP pollution, and sewage management failures, necessitating that concerned authorities should implement policies and measures to curb the negative impacts on the environment and public health.

Designing Cu chemical distribution in Ti(AlCu)N coatings for enhanced erosion-corrosion and antibacterial performance

In order to enhance the erosion-corrosion resistance and antibacterial property simultaneously, we prepared PVD TiAlCuN coatings with periodically modulated TiAlCuN/TiAlN sublayers near the topmost surface. Firstly, Ti(AlCu)N phase and Cu nano-precipitates formed in TiAlCuN sublayers can improve coating mechanical performance. Secondly, apart from reducing galvanic corrosion potential, the Cu ions could preferentially diffuse upward to the topmost surface, along the grain boundaries in the columnar TiAlN sublayers, leading to Cu ions at the topmost surface and good antibacterial property. The interfaces between TiAlN and TiAlCuN sublayers can act as multiple barriers to crack propagation and prevent severe coating spallation. The optimized coating exhibits i) the lowest cumulative mass loss and erosion-corrosion rate after 24 h erosion-corrosion testing, which associates with the improved mechanical property and good corrosion resistance, and ii) excellent antibacterial property against Escherichia coli (E. coli) with an antibacterial rate of 99.68 % and a live/dead bacteria proportion of 7.40 %/92.60 %, due to the advanced homeostasis work of the primordial surface Cu ions. The design of modulating the surface Cu chemical distribution achieved by subsurface column-layer architecture provides a new design concept for incorporation of Cu in coatings for the applications of metal parts in critical marine environment.

Enabling sustainable transportation through joining of dissimilar lightweight materials

Abstract

Electrochemical Corrosion Study of Weld Joint of Nb and Ti6Al4V in Saline and Water

A Type 1 niobium (Nb) part and a grade 5 titanium (Ti6Al4V) part were joined by laser weld, to form a component to be used in implantable medical devices for electrical stimulation therapies. This component could be exposed to body fluid or particularly water which could penetrate through the medical adhesive seal over the time of implantation. To meet the device reliability, performance, and patient safety goals, electrochemical immersion testing was conducted to study corrosion of the base metals and their galvanic couples and to evaluate corrosion resistance of the weld joints. Samples of as-manufactured Ti6Al4V parts, Nb parts, and weld joints were prepared, cleaned and inspected for testing (Figure 1, Table 1). A wire made of the same material and mostly sealed by medical adhesive, was welded to each sample for electrical connection. The surface areas of samples were calculated. They were divided into groups and tested at 37°C in glass jars containing de-ionized (DI) water or phosphate buffered saline (PBS), respectively. Electrochemical tests including open circuit potential (OCP); cathodic polarization (CP) or anodic polarization (AP); galvanic corrosion or zero resistance ammeter (ZRA) testing; anodic cyclic polarization (ACP) and potentiostatic polarization (PP) were performed at different times during immersion of the samples. The potentiodynamic scan rate for CP, AP and ACP scans was 0.2 mV/s. The tests used three-electrode configuration consisting of a working electrode (WE) which was the testing sample; a reference electrode (Ref.) which was a Ag/AgCl electrode in 3 M NaCl solution; and a counter electrode (CE) which was a piece of platinum sheet, or for galvanic corrosion testing, which was the secondary working electrode of the Nb/Ti6Al4V galvanic couple. Visual and stereomicroscopic examinations were made during and after the testing with a total of immersion time of about 100-130 days. After 3-4 days of immersion, OCP was stabilizing with an average of about 0.08, 0.05 and 0.07 V vs. Ref. in DI water and 0.11, -0.02 and 0.06 V vs. Ref. in PBS, for the Ti6Al4V, Nb and joint samples, respectively. Though the OCP difference was small, it indicated Nb would act as anode when joined or coupled to Ti6Al4V. Galvanic corrosion could occur in Nb of the joint, especially considering the anode (Nb) to cathode (Ti6Al4V) area ratio was as small as 0.01. A galvanic current was estimated to be about 9-13 nA/cm2 in DI water and 24-42 nA/cm2 in PBS based on anodic polarization of Nb and cathodic polarization of Ti6Al4V in potentiodynamic scans (Figure 2a). Further, galvanic corrosion potential and current (Figures 2b and 2c) of the Nb/Ti6Al4V couples was measured by ZRA testing. After ~48 days of testing, the galvanic current was stabilized with an average of about 1 nA/cm2 in both DI water and PBS, indicating a stable passive film formed on Nb surface. The average galvanic corrosion rate of Nb of the couples was about 0.008 μm/year in both DI water and PBS, calculated from the measured galvanic current which was considered more accurate (as obtained in a more steady state) and much lower than the estimation from potentiodynamic scans. ACP curves of the joint and base metal samples showed similar polarization behavior in both DI water and PBS (Figure 2d). All samples displayed stable passivation with low current from OCP to a potential of Ep ≅0.8 V vs. OCP. Beyond Ep, current increased markedly, and small hysteresis formed in ACP scans for the joint and Nb samples. Additional potentiostatic polarization was thus performed on the joint and Nb samples in PBS for ~4 days at potentials of 1.2 V and 1.4 V vs. Ref. which were above Ep and in the hysteresis range. The current would stabilize at the increased levels for both potentials. Neither localized pitting or crevice corrosion attack nor active gas bubbling was observed on the joints and parts. Corrosion rate estimated from the increased current at 1.4 V vs. Ref. for Nb could be as high as 66 μm/year. Depending on the type of device design, an electrochemical potential possibly applied to the joint component was assessed under simulated electrical signals for stimulation, which was measured to be under 0.3 V vs. Ref. and smaller than Ep. Therefore, the joint materials of Nb and Ti6Al4V are stable and suitable for the device application with no concern of corrosion. Figure 1

해양구조물의 방식을 위한 알루미늄 합금의 희생양극적 부식 특성의 전기화학적 평가

The corrosion behavior of metals and alloys for the safety of offshore structures in seawater was investigated for the application of sacrificial anodes. The experiments were focused on the polarization behaviors and the surface morphology of each metal after experiments. Pure Zn, pure Al (Al1050), Al alloys (Al5052, Al6061), Mg alloys (AZ31, AZ91D) and steel (SCM440) were assessed in 3.5% sodium chloride solution by means of potentiodynamic polarization to verify the galvanic corrosion potential (). Potentiostat plots were plotted to compare the surface and corrosion current density () of metals as sacrificial anodes in seawater to protect steel alloy as a cathode. Al alloys showed the best performance as a sacrificial anode, on the other hand, Mg alloys showed overprotection behavior. The surface morphologies of sacrificial anodes were observed by FESEM and compared.

Galvanic Corrosion of 70-30 Copper-Nickel Alloy in Contact with Nickel-Aluminum Bronze in Simulated Deep Sea Environment

The galvanic corrosion behavior of 70-30 copper-nickel alloy as a brand new seawater pipe material and nickel-aluminum bronze as the commonly used pipe valve material in simulated low temperature conditions of deep sea was studied. The galvanic corrosion potential and galvanic current density of the pair were monitored, and the galvanic corrosion tendency and effect at different temperature were evaluated. Combined with the electrochemical measurements, the influence of seawater temperature on galvanic corrosion behavior was also discussed. The results showed that as the result of coupling, 70-30 copper-nickel alloy acting as the coupled cathode was prevented from corrosion, while nickel-aluminum bronze became the sacrificial anode. With the decrease of seawater temperature, the galvanic corrosion tendency and galvanic corrosion rate of the pair decreased. The change in galvanic corrosion tendency with seawater temperature was attributed to the different electrochemical properties induced by the inherent difference in chemical compositions of the alloys. The low galvanic corrosion rate and effect were related to the reduced mass transfer rates at low temperature. Moreover, the electrochemical behavior of the copper alloys was much sensitive to the change in the amount of dissolved oxygen at the lower seawater temperature, especially for the alloy with higher passivation ability, i.e., 70-30 copper-nickel alloy.

Effects of Surface Oxide Coating on Corrosion Behavior of Ti-1023/LY12 Galvanic Couple

Galvanic corrosion behavior of Ti-1023 titanium alloy coupled to LY12 aluminum alloy was investigated in 3.5% NaCl solution. Particular attention was given to the effect of anodized coatings on corrosion behaviors of Ti-1023/LY12 galvanic couple. Galvanic test was conducted on the following couples: Ti-1023/LY12, Ti-1023/anodized LY12 and anodized Ti-1023/anodized LY12, respectively. Corrosion properties including open circuit potential (Eoc) of each material, galvanic corrosion potential (Eg) and galvanic corrosion current (Ig) of the couples were monitored. Corrosion morphology was observed by optical microscope (OM) and corrosion mechanisms were analyzed and discussed. It was showed that anodized coatings significantly decreased Eg and Īg of the couples and provide effective protection of the anode from suffering corrosion attack. Only slight localized corrosion was detected on anodized LY12 alloy in the two anodized couples and the LY12 in anodized Ti-1023/anodized LY12 couple was found to be least susceptible to galvanic corrosion. The LY12 alloy in the bare couple: Ti-1023/LY12, was found to be highly susceptible to galvanic corrosion and suffered severe uniform and localized corrosion attack

Study on Corrosion Behavior of Ti-Ni-Nb Shape Memory Alloy and 1Cr18Ni9Ti Stainless Steel Aeroplane Pipe System

The susceptibility to stress corrosion cracking (SCC) and galvanic corrosion of an aeroplane pipe made of 1Cr18Ni9Ti connected with a pipe coupling that made of Ti-Ni-Nb shape memory alloy were evaluated. SCC test was completed under simulated service environment in 6% NaCl solution through a self-designed corrosive system. Galvanic corrosion behavior of Ti-Ni-Nb/1Cr18Ni9Ti couple was conducted in 3.5% NaCl solution at 30°C, in which galvanic corrosion current (Ig) and galvanic corrosion potential (Eg) were monitored. The corrosion morphology was observed by using scanning electronic microscope (SEM) and optical microscope (OM) after SCC test and galvanic test. It was showed that no obvious corrosion was detected on the surface of the whole pipe system after the simulated test. The two metals showed excellent resistance to SCC based on the section morphology observation. The average galvanic corrosion current of 1Cr18Ni9Ti/Ti-Ni-Nb couple was 0.13µA/cm2. No obvious corrosion pitting was detected on the surface of the two alloys by OM observation. Therefore, 1Cr18Ni9Ti pipe was safely connected with Ti-Ni-Nb pipe coupling in aeroplane pipe system.

Comparison of Galvanic Corrosion Potential of Metal Injection Molded Brackets to that of Conventional Metal Brackets with Nickel-Titanium and Copper Nickel-Titanium Archwire Combinations

The aim of the study is to investigate the galvanic corrosion potential of metal injection molding (MIM) brackets to that of conventional brackets under similar in vitro conditions with nickel-titanium and copper nickel-titanium archwires. Twenty-five maxillary premolar MIM stainless steel brackets and 25 conventional stainless steel brackets and archwires, 0.16 inch, each 10 mm length, 25 nickeltitanium wires, 25 copper nickel-titanium wires were used. They were divided into four groups which had five samples each. Combination of MIM bracket with copper nickel-titanium wire, MIM bracket with nickel-titanium wire and conventional stainless steel brackets with copper nickel-titanium wire and conventional stainless steel brackets with nickel-titanium wires which later were suspended in 350 ml of 1 M lactic acid solution media. Galvanic corrosion potential of four groups were analyzed under similar in vitro conditions. Precorrosion and postcorrosion elemental composition of MIM and conventional stainless steel bracket by scanning electron microscope (SEM) with energy dispersive spectroscope (EDS) was done. MIM bracket showed decreased corrosion susceptibility than conventional bracket with copper nickeltitanium wire. Both MIM and conventional bracket showed similar corrosion resistance potential in association with nickel-titanium archwires. It seems that both brackets are more compatible with copper nickel-titanium archwires regarding the decrease in the consequences of galvanic reaction. The EDS analysis showed that the MIM brackets with copper nickel-titanium wires released less metal ions than conventional bracket with copper nickeltitanium wires. MIM brackets showed decreased corrosion susceptibility, copper nickel-titanium archwires are compatible with both the brackets than nickel-titanium archwires. Clinically MIM and conventional brackets behaved more or less similarly in terms of corrosion resistance. In order to decrease the corrosion potential of MIM brackets, more precise manufacturing technique should be improved to get a more smoother surface finish.

Galvanic Corrosion between Depleted Uranium and 40Cr Steel

Individual corrosion and galvanic corrosion behaviors of depleted uranium (DU) and 40Cr steel were investigated by electrochemical analyzing technologies in 3.5w.t%NaCl solution, including open circuit potential(OCP) test, linear polarization(LP) test, potentiodynamic polarizaition(PD) test, galvanic corrosion potential and corrosion current density test. The results reveal that the OCP of DU and 40Cr steel are around -790mV and -660mV, respectively. 40Cr has a higher linear polarization resistance than DU in galvanic corrosion. The dynamic processes of galvanic corrosion goes through an conversion in the whole test period. DU acts as anode with an accelerated corrosion rate, while the 40Cr steel behaves as cathode during the process of galvanic corrosion for DU/40Cr couple. The galvanic potential and current density of the DU/40Cr couple are -780mV and 17.5μA/cm-2, respectively.

Hydrogen entry behaviour of newly developed Al–Mg–Si coating produced by physical vapour deposition

A ternary Al–Mg–Si alloy was prepared by co-evaporation technique and tested with respect to hydrogen entry behaviour as an alternative to conventional zinc coating on steel. Hydrogen entry behaviour evaluated using Devanathan cell showed a smaller hydrogen entry for this new coating than conventional zinc coating. Compared to an unscratched surface, hydrogen entry increased by more than 100 times in the scratched surface, but it was lower than that for the zinc coating with a scratched surface owing to the moderate galvanic corrosion potential of the new coating. This new coating is proposed especially for high-strength steel application.

高温高圧 O2-CO2 下における NaCl 水溶液中の Fe-Zn ガルバニ腐食

Electrochemical characteristics of a Fe-Zn galvanic couple were studied under O2-CO2 mixtures of 2 MPa in a 3 mass% NaCl solution at 423 K for 14.4 ks. In 100% O2 and in 10% CO2+90% O2, both the galvanic corrosion current and corrosion potential of the couple remarkably changed after a certain period. Then, the polarities of the galvanic corrosion currents of the couple were reversed, indicating that Fe was not protected any more and rather corroded at an accelerated rate. On the other hand, the polarities of the current of the couple in 20% CO2+80% O2 and in 100% CO2 were not changed during the immersion time, indicating that Fe was still protected, although the galvanic currents were very low in 100% CO2. The galvanic corrosion potentials were always close to the corresponding cathodic potentials, indicating that the corrosion is governed by cathodic control. In 10% CO2+90% O2 and in 100% O2, the polarization characteristics of Zn specimen before and after the immersion test drastically changed, indicating that the galvanic couple of Zn anode and Fe cathode before the test changed to the couple of Fe anode and Zn cathode after the test. But, in 20% CO2+80% O2 and in 100% CO2, the galvanic couple of Zn anode and Fe cathode was hold during the immersion time. As CO2 ratio decreased, the corrosion products on the surface of Zn changed in the sequence: ZnCO3→Zn5(CO3)2(OH)6→Zn5Cl2(OH)8→ZnO. Above results show that Zn specimen in a Fe-Zn couple acts as a cathode due to the formation of ZnO on Zn. Therefore, whether Zn acts as a sacrificial anode or not, depends on the possibility of the formation of ZnO on Zn.

Effects of electroplated coatings on corrosion behavior of Ti-1023/30CrMnSiA galvanic couple

Galvanic corrosion behavior of Ti-1023 titanium alloy coupled 30CrMnSiA steel was investigated in 3.5% NaCl solution. Particular attention was given to the effect of three different electroplated coatings on corrosion behavior of the galvanic couple. Galvanic corrosion test was conducted on Ti-1023 titanium alloy which coupled Ni-electroplated 30CrMnSiA, Zn-electroplated 30CrMnSiA, Cd-electroplated 30CrMnSiA and bare 30CrMnSiA, respectively. Corrosion properties including open circuit potential (E oc ), galvanic corrosion potential (E g ), and galvanic corrosion current (I g ) were monitored. Corrosion morphology was observed by optical microscope (OM) and corrosion mechanism was analyzed and discussed. The results show that the three electroplated coatings improve the corrosion resistance of the anode in different magnitudes. Ni-electroplated 30CrMnSiA and Cd-electroplated 30CrMnSiA coatings are found to be least susceptible to galvanic corrosion when coupled Ti-1023 titanium alloy. Zn-electroplated 30CrMnSiA is moderately susceptible to galvanic corrosion. But the bare 30CrMnSiA is highly susceptible to galvanic corrosion in corrosive environment.

Effects of Ti-1023 Anodized Coating on Corrosion Behavior of Ti-1023/30CrMnSiA and Ti-1023/LY12 Galvanic Couples

Galvanic properties were evaluated on bare and anodized Ti-1023 titanium alloy which coupled to Ni-electroplated, Zn-electroplated, Cd-electroplated 30CrMnSiA and anodized LY12, respectively. Corrosion properties including open circuit potential (Eoc) of each material, galvanic corrosion potential (Eg), and corrosion current (Ig) of the couples were monitored in conjunction with a Model 263A potentiostat system. Corrosion current density (Īg) and average value of corrosion potential (Ēg) were calculated from Ig-time and Eg-time curves, respectively. Corrosion morphology was observed on a optical microscope (OM) and corrosion mechanisms were analyzed and discussed. The corrosion resistance of Ti-1023/LY12 couple was significantly improved by Ti-1023 anodized coating. However, the coating accelerated the dissolve of the three electroplated coatings in the other galvanic couples, resulting in a heavy corrosion attack on 30CrMnSiA steel.

Corrosion and impressed current cathodic protection of copper-based materials using a bimetallic rotating cylinder electrode (BRCE)

A bimetallic rotating cylinder electrode (having individual electrode areas of 10 cm 2 and rotating at 200–1400 rpm) has been used to examine the corrosion and protection characteristics of copper/nickel aluminium bronze and 90–10 copper–nickel/nickel aluminium bronze galvanic couples in filtered seawater at 25 °C. The flow-influenced electrochemistry of the systems was determined using zero resistance ammetry, corrosion potential measurements and a potential step current transient technique. In each case, the galvanic corrosion potential and corrosion rate displayed a Reynolds number dependency where mass transport control of the anodic dissolution reaction partially controlled the reaction rate. Bimetallic impressed current cathodic protection (ICCP) has also been demonstrated for a range of applied protection potentials and Reynolds numbers. A comparison has been made between the directly measured bimetallic ICCP current demand and that determined from independent, single-metal rotating cylinder electrode measurements. In this case, the mixed charge and mass transport controlled rate of oxygen reduction was examined.