Electrochemical Corrosion Characteristics Research Articles

Evaluation of the mechanical and corrosion protection performance of electrodeposited hydroxyapatite on the high energy electron beam treated titanium alloy

In our present study, the Ti–6Al–4V alloy surface was modified by irradiating with the high energy low current DC electron beam (HELCDEB) using 700keV DC accelerator. Following this, the HELCDEB treated surface was coated with hydroxyapatite by adopting electrodeposition method. The microstructure and hardness of HELCDEB treated Ti–6A1–4V alloy with and without electrodeposited hydroxyapatite were investigated. Also, the electrochemical corrosion characteristics of the samples in simulated body fluid (SBF) was studied by potentiodynamic polarisation and electrochemical impedence techniques (EIS) which showed an enhanced corrosion resistance and revealed an improved life time for the hydroxyapatite coating developed on the HELCDEB treated Ti–6A1–4V alloy than the untreated sample.

Electrochemical corrosion characteristics of type 316L stainless steel in hot concentrated seawater

The corrosion behaviour of 316L stainless steel was studied in the concentrated artificial seawater at 72°C, i.e., the simulated low temperature-multi effect distillation environments, by using electrochemical measurement techniques. The corrosion state changes from spontaneous passivation to pitting after about 1150h of immersion. Pitting corrosion is under mixed control of charge transfer and diffusion processes in the long-term immersion. The salt deposits retard the diffusion of oxygen to the metal surface. The pit depth only reaches about 38μm after one year of immersion due to the alloying effect of Mo, low dissolved oxygen levels and weak occlusion states.

Localized Electrochemical Corrosion Characteristics of Carbon Steel in Seawater

The galvanic and potential distributions of carbon steel immersed in seawater were studied by wire beam electrode (WBE) technique. Results indicated that the corrosion of carbon steel in seawater tended to local corrosion. With immersion time increasing, local corrosion was more and more serious. During the initial immersion period, the top of the coupon near the water surface was main cathode. With the corrosion extended, corrosion products gradually gathered on the surface of the carbon steel. Potential differences between cathode and anode gradually became small. Cathode and anode redistributed on the surface of carbon steel. At last, the top and the bottom were cathode while the middle was anode. The areas of anode first increased and then decreased. The areas of cathode were in contrast.

Complex Behavior Using the Hybrid Method of Cavitation and Electrochemical Corrosion for Casted Al Bronze

The sustainable development of engineering, mechanical instrument requires higher speed and higher power. It cause a physical damage is excessive damage for underwater rotating system as cavitations and erosion, but also electrochemical corrosion by chloride ion and flow of current in marine environment. In this study, we assessed electrochemical corrosion characteristics of aluminum-bronze that are the material for the underwater rotating system used in the ocean industry and studied the complex behavior of electrochemical corrosion and cavitation corrosion through the hybrid test that also included cavitation corrosion environment. After the cavitation hybrid tests, surface of specimens are observed to measurement damage degree using 3D optical microscope and compared the average of damage depth by immersion time. The observation of the surface micro-structure suggested that the corrosion took place initially in β phase that has poor corrosion resistance in spite of high hardness.

Investigation of Wear and Corrosion Protection of AlSi20 Coatings Produced by Plasma Spraying and Laser Cladding on AZ31B

Magnesium and magnesium alloys are the lightest structural materials with an approximate density of 1.7 g/cm2 (density of aluminum ~2.7 g/cm2). Due to poor corrosion and wear resistance properties, they need to be coated for usage in service conditions under corrosive and tribological loads. AlSi20 was found to be a suitable coating material to improve the wear and corrosion protection properties of magnesium alloys. Within this work, AlSi20 coatings were applied by plasma spraying, laser cladding, and a combination of both processes. First, the coatings are characterized by their microhardness and residual stresses formed within the coating during the different coating processes. Then, these coatings were investigated regarding corrosion resistance in 3.5% sodium chloride solution in a three-electrode setup to obtain electrochemical corrosion characteristics. Abrasive wear was investigated using a pin-on-disk tribometer and the abrasion rate was calculated. Resistance against shock loads was tested by applying a cyclic load at 50 Hz to investigate the resistance against impact stresses.

Effect of In, Bi, Zn Binary-Metal Dopings in Sn-0.7Cu Solder on its Electrochemical Corrosion Charateristics in 3 wt.% NaCl Solution

Effect of In, Zn, Bi binary-metal dopings in Sn-0.7Cu (SC) solder on the electrochemical corrosion characteristics of SC solder were conducted, the potentiodynamic polarization test coupled with SEM analyses had been widely used to study the corrosion properties of alloy materials. The results showed that when both In-Zn binary-metal doping was increased, the corrosive current density (Icorr) increased, which proved that anti-corrosion capacities of Sn-0.7Cu solder decreased with In-Zn doping increasing, the affected order was Zn>In. When both In-Bi binary-metal doping percent were increased, the corrosive current density (Icorr) decreased, the affected order was In>Bi. When both Zn-Bi binary-metal doping percent were increased, the Icorr increased, the affected order was Zn>Bi. There was collaborated function on SC solder for the three metals. The synthesized result showed that the sequence of In, Bi, Zn affecting on corrosion of SC solder was that Zn>In>Bi, which provide a support data to improve soldering reliability in electronic packagings.

Kinetic regularities and mechanism of formation of nanosize passive films on titanium alloys for medical application and their electrochemical behavior in simulated physiological media

Chronopotentiometry and potentiodynamic voltammetry simulated were used to study the electrochemical behavior of the new pseudoelastic medical Ti-Nb-Ta alloy in simulated physiological media (neutral and acidified Hank’s solution, artificial saliva) at temperatures of 37 and 50°C as compared to titanium and nitinol. The mechanism of formation of protective passive films on the alloy surface is proposed on the basis of analysis of kinetic regularities used to establish steady-state potentials during exposure to the corresponding solutions. X-ray photoelectron spectroscopy technique was used to study the composition of passivating layers on the surface of the Ti-Nb-Ta alloy after corrosion tests. It is found that the new alloy is as good as titanium as regards its corrosion-electrochemical characteristics and is not subjected to pitting corrosion, as opposed to nitinol.

Influences of the three‐phase boundary on the electrochemical corrosion characteristics of carbon steel under droplets

AbstractThe potential/current distributions of carbon steel were investigated under 0.001 M sodium chloride droplets of various sizes using a wire beam electrode. During the corrosion process, carbon steel exhibited heterogeneous electrochemical characteristics with the major anodes located near the edge of the droplets. The three‐phase boundary (TPB) plays a vital role in determining the electrochemical distribution and the corrosion degree of carbon steel. With the increase of droplet size, the average anodic current density and the corrosion degree decreased, which is believed to be due to the decrease of the TPB length per unit area.

Corrosion Electrochemical Characteristics of the Passive Films Formed on Inconel 718 Alloy in the Environments Containing High H<SUB>2</SUB>S and CO<SUB>2</SUB> Partial Pressures

Corrosion Electrochemical Characteristics of the Passive Films Formed on Inconel 718 Alloy in the Environments Containing High H<SUB>2</SUB>S and CO<SUB>2</SUB> Partial Pressures

Microplasma electrochemical deposition of aluminum oxide-polyethylene composite coatings on iron surface

Composite coatings containing aluminum oxide and polyethylene are deposited using microplasma electrochemical anodic treatment of the iron surface in an aluminate bath at a voltage of 260–360 V. Using scanning electron microscopy, microprobe analysis, Fourier transform infrared spectroscopy, and electrochemical polarization measurements, the composition, structure, and corrosion characteristics of the coatings are determined. Adding 0.5–1.0 wt % polyethylene dispersion to the electrolyte is shown to substantially facilitate the origination of microplasma conditions, prevent the strong warming of electrolyte during anodizing, and obtain coatings with substantially higher corrosion resistance compared to those produced in an aluminate bath containing no polymer dispersion.

Temperature dependence of the electrochemical corrosion characteristics of carbon steel in a salty soil

The electrochemical corrosion characteristics of carbon steel in a salty soil at different temperatures were studied by measurements and analyses of potentiodynamic polarization curves, linear polarization resistance and electrochemical impedance spectroscopy. The results showed that the mass-transfer of dissolved oxygen plays an essential role in carbon steel corrosion, and the whole corrosion process is mix-controlled by both activation and mass-transfer steps. Passivity can be developed on carbon steel in the soil at low temperatures. With the increase of temperature, the passive current density increases and the passive potential range decreases. When temperature is elevated to a certain value, 50 °C in this system, passivity cannot be maintained and the steel is dominated by an active dissolution status. Anodic Tafel slope decreases continuously with the increase in temperature, which is mainly due to the enhanced electrode reaction rate at an elevated temperature. Simultaneously, cathodic Tafel slope increases with temperature continuously due to the decrease of the solubility of dissolved oxygen in soil. Since the diffusion activation energy is generally much smaller than the reaction activation energy, the effect of temperature on diffusion is far less than that on electrode reaction rate.

Corrosion Electrochemical Characteristics of X60 Pipeline Steel in SRB and CO<SUB>2</SUB> Coexistence Environment

Corrosion Electrochemical Characteristics of X60 Pipeline Steel in SRB and CO<SUB>2</SUB> Coexistence Environment

Effect of vacuum ion-plasma treatment on the electrochemical corrosion characteristics of titanium-alloy implants

The effect of mechanical polishing and various types of vacuum ion-plasma treatment of model implants made of VT1-0, VT20, and VT6 titanium alloys on their electrochemical corrosion characteristics in a 0.9% NaCl solution (Ringer’s solution) is studied. Ion nitriding and the evaporation of a titanium nitride coating are shown to form a surface structure that provides an increase in the hardness, wear resistance, and corrosion resistance of these implants.

Corrosion Fatigue Characteristics of Artificially Degraded CF8A Steel in 3.5 WT.% NaCl Solution

CF8A steel is a material of the piping system in nuclear power plant. In order to evaluate its fracture characteristics and degradation by corrosion, electrochemical corrosion and corrosion fatigue characteristics were evaluated. CF8A steel was artificially degraded at 400°C for 3 months. Corrosion rate of degraded CF8A steel in NaCl solution of room temperature increases with concentration of NaCl solution increase. However, concentration of NaCl solution will be more than 4.0wt.%, it shows decreasing tendency. Crack growth rates of degraded and not-degraded CF8A steel in air condition do not show remarkable difference. However, in 3.5wt.% NaCl solution, it showed higher than that of in air.

Hydrogen absorption and corrosion resistance of LaNi 4.8Al 0.2 and LaNi 4.8Al 0.1Li 0.1 alloys

The hydrogen absorption properties and the electrochemical corrosion characteristics of LaNi 4.8Al 0.2 and LaNi 4.8Al 0.1Li 0.1 alloys were investigated in this study. The structure of the alloys was tested by X-ray diffraction (XRD) method. The ability of alloys to absorb hydrogen was characterized from the pressure–composition ( P– C) isotherms at temperatures ranging from 293 to 353 K. The P– C isotherms allowed to determine thermodynamic parameters for the hydrogen desorption process. It was found that the alloys were solid solutions of CaCu 5 type structure. Partial substitution of Al with Li in the alloy led to increase of the amount of absorbed hydrogen and the related plateau pressures. On the basis of potentiokinetic polarisation characteristics, it was demonstrated that the presence of Li in the alloy was advantageous from corrosion resistance point of view.

Mo and W as alloying elements in Co-based alloys—their effects on erosion–corrosion resistance

In this paper results from erosion–corrosion tests performed under liquid–solid erosion conditions in 3.5% NaCl liquid medium are reported. The focus of the paper is to compare the behaviour of Stellite alloy 706 which contains 5 wt.% molybdenum with Stellite alloy 6 which contains 4.8 wt.% tungsten, both in cast and Hot Isostatically Pressed (HIPed) form, in terms of their electrochemical corrosion characteristics, their resistance to mechanical degradation and relationship between microstructure and degradation mechanisms. It has been shown that both cast and HIPed Stellite 706 possess better erosion and erosion–corrosion resistance than Stellite 6 counterparts under a wide range of conditions. The significant role of the microstructure and specifically the type of carbides in affecting the erosion–corrosion performance of the alloys is demonstrated and discussed. Also it has been shown that in these multiphase alloys there is no direct relationship between the hardness and erosion–corrosion resistance.

Corrosion electrochemical characteristics of red iron oxide pigmented epoxy coatings on aluminum alloys

Red iron oxide pigmented epoxy coatings were prepared on aluminum alloys and were characterized by electrochemical impedance spectroscopy (EIS) immersed in NaCl solution. The evolutions of impedance models of coated metals were obtained by the fitting analysis of experimental data using suitable equivalent electrical circuits (EEC). The results indicated that the composite electrode system could be fitted by three impedance models. At the initial immersion stage, coatings acted as a barrier layer and only performed a simple circuit consisting of a coating resistance ( R c) parallel to a coating capacitance ( C c). After a certain time of exposure, water and (or) oxygen arrived at the metal surface through the coating, leading to the formation of electrochemical corrosion sites at metal interface and thereby the appearance of double-layer capacitance ( C dl) and charge transfer resistance ( R ct). After intensive attacking of metal substrates, the mass transfer of corrosion products was in difficulty. In this case, the diffusion elements were added to the EEC. It was found that due to the presence of inert pigment particles, the mass transfer behaviors were interestingly different from those of the varnish polymer coatings. Electrical parameters were also obtained from the EIS data. ln C c–time curve showed a Case II water sorption kinetics, typical non-Fickian diffusion for water uptake.

Use of Advanced Thermal Spray Processes for Corrosion Protection in Marine Environments

The microstructure and aqueous electrochemical corrosion characteristics of stainless steel 316L (UNS S31603) and nickel alloy 625 (UNS N06625) coatings deposited onto a carbon steel substrate using commercial high velocity oxyfuel (HVOF) spraying systems and a new high velocity wire flame spraying system were assessed. The electrochemical corrosion behaviour of the as prepared coatings was compared with their respective materials in wrought form. A HVOF sprayed coating of nickel alloy 625 was found to be more corrosion resistant in an aqueous saline environment than a coating of stainless steel 316L. However, the nickel alloy coating did not match the corrosion resistance of the same nickel alloy in wrought form, but may have the ability to offer corrosion resistance in saline aqueous environments approaching that of a wrought stainless steel. A porosity level of < 2.5% may not have a significant effect on the electrochemical activities of the HVOF sprayed coatings near the free corrosion (rest) potential. However, the level of oxidation depending upon the spraying system was shown to have an effect on the corrosion resistance of the sprayed coatings. The stainless steel and nickel alloy coatings produced using the high velocity wire flame spray system displayed much higher oxides compared with those produced using HVOF processes and. consequently, poorer corrosion resistance.

Electrochemical corrosion properties of Ti–6Al–4V implant alloy in the biological environment

The electrochemical corrosion behavior of Ti–6Al–4V implant alloy was investigated in three biological solutions, i.e. urine, serum and joint fluid. The corrosion properties of Ti–6Al–4V implant alloys were examined by using electrochemical techniques, such as the potentiodynamic method, cyclic voltammetry, electrochemical impedance spectroscopy (EIS). The electrochemical corrosion characteristics of Ti–6Al–4V implant alloys in three biological solutions were measured in terms of the corrosion potential ( E corr ), the corrosion current density ( i corr ), and ac polarization resistance ( R p ). The corrosion kinetic parameters were calculated from both the Tafel plot analyses and EIS analyses. The dependence of impedance versus potentials was studied at 37 °C at various offset potentials in three biological solutions. The ac circuit model for Ti–6Al–4V implant alloy at corrosion interface in biological solution was proposed, which was based on a simple Randles equivalent circuit. It was found that the Ti–6Al–4V implant alloy in three biological solutions showed a characteristic of a capacitive behavior. The experimental results of Tafel plot analyses were found in good agreement with that of EIS analyses.

Cavitation resistance of VT5 alloy after surface mechanical pulsed treatment

The mechanical pulsed hardening of VT5 α-titanium alloy in the course of the friction contact of the working surface with a special tool in various technological media significantly increases its resistance to cavitation-erosion wear. Moreover, the corrosion-electrochemical characteristics remain high and the microhardness of the surface becomes 2–2.5 times higher. This leads to the increase in the cavitation-erosion resistance of the material. The obtained effect depends on the composition of the applied technological medium. The liquid intended for carbonization proves to be more efficient for increasing the wear resistance of the alloy than the PMS-100 liquid.