Anodic Corrosion Rate Research Articles

Kinetic investigation of sulfur corrosion: First principles calculations

The expressions of two important kinetic parameters (chemical activation energy of electrode reaction and absolute potential of equilibrium state) that determine the reaction rate during the anodic dissolution reaction are derived from the thermodynamic and kinetic relationships of the anodic dissolution reaction, the relationship between absolute potential and current density in the anode dissolution process is constructed. Under the framework of first principles, the calculation model of the electrochemical corrosion anodic dissolution reaction is proposed. Density functional theory study of the process of dissolving Fe atoms from the surface of Fe(111) alloy models in vacuum and explicit water molecules. The addition of water molecules and sulfur atoms promotes charge transfer during dissolution and increases the corrosion rate, while water molecules reduce the work function, while S goes increases the work function. Through the corrosion current density model of activation energy, the role of alloy dissolution kinetics with different alloys added was explored. The analysis shows that the addition of Mn and Cr can greatly reduce the anodic corrosion rate and increase the corrosion resistance of Fe.

Electrochemical interaction behaviours between adjacent coating defects in steel structure associated with corrosion acceleration effects

The corrosion interaction mechanism of carbon steel was studied to address the mutual interference of carbon steels under coating defects in the atmospheric environment. The findings revealed that the electrochemical interactions between the carbon steels were primarily influenced by the solution resistance, cathode area, and cathode-to-anode area ratio. In addition, the upper limit of the accelerating effect of the macrocell current on the anodic corrosion rate was determined by theoretical deduction. Finally, the corrosion-accelerating effect of the macrocell current was determined to assess the corrosion rate of carbon steels with electrochemical interactions under defects.

Effect of Chloride Concentration on Stress Corrosion Behavior and Mechanism of SA516Gr70N Steel in Alkaline NaCl/Na2S Solution

The effects of chloride on the electrochemical process and susceptibility to stress corrosion cracking (SCC) of SA516Gr70N steel in alkaline NaCl/Na2S solution were investigated by using electrochemical techniques (impedance spectroscopy and polarization curve measurement) and slow strain rate tensile (SSRT) tests. SA516Gr70N steel exhibited SCC susceptibility to a certain extent in alkaline NaCl/Na2S solution. The susceptibility to SCC decreased with increasing chloride concentrations in solutions with pH values of 9 and 11, while susceptibility was not apparent in higher pH solutions. Electrochemical analysis showed that the corrosion potential became more negative, and the anodic corrosion rate decreased with increasing chloride concentration due to the competitive adsorption of HS− and Cl−. The mechanism of SCC is mainly controlled by anodic dissolution with the addition of chloride.

An Effect of Nickel Additives on Anode Behavior of Zinc-Aluminum Alloys Zn5Al, Zn55Al in NaCl Electrolyte

The results of studying the anodic behavior of Zn5Al, Zn55Al alloys doped with nickel in a NaCl electrolyte are presented. It was found that nickel additives in an amount of 0.01-0.5 wt % contribute to a decrease in the anodic corrosion rate of the initial Zn5Al and Zn55Al alloys by approximately 15-20%. It is shown that alloying the initial alloys with nickel shifts the potentials of free corrosion, pitting and repassivation to the positive region. The proposed compositions of zinc-aluminum alloys containing nickel can be used as an anode coating for corrosion protection of metal structures for various purposes, including steel structures and structures.

Failure investigation of stainless steel anodes used in gold electrowinning

Failure of austenitic stainless steel anodes in a gold electrowinning process (EW) was reported after a short period of service (3–6 weeks). Different analytical and characterization techniques were employed to conduct root cause failure analysis (RCFA) of the failed anodes. Electrochemical behaviour of the stainless steel alloy in the industrially supplied and synthesized electrowinning solutions were evaluated using different electrochemical test methods. The main failure mechanism of these anodes was found to be transpassive dissolution. Local solution acidification in the pores and crevices also contributed to the high corrosion rate of the stainless steel anodes as the transpassive dissolution rate increases when the pH of the electrowinning solution decreases. Gold and silver were found in the anodic layer along with typical stainless steel corrosion products (iron and chromium oxides), contributing to gold loss in the electrowinning process. Materials selection, design change, solution and process modifications are recommended to prevent similar failures or maximize the lifetime of the anodes.

Effect of Surface Nanocrystallization on Corrosion Resistance of the Conformed Cu-0.4%Mg Alloy in NaCl Solution

Surface nano-crystallization (SNC) of a conform-extruded Cu-0.4 wt.% Mg alloy was successfully conducted by high-speed rotating wire-brushing to obtain the deformed zone with dislocation cells and nanocrystallines. SNC promotes the anodic dissolution and corrosion rate of the Cu-Mg alloy in the initial stage of immersion corrosion in 0.1 M NaCl solution. The weakened corrosion resistance is mainly attributed to the higher corrosion activity of SNC-treated alloy. With extending the immersion time, the SNC-treated alloy slows the corrosion rate dramatically and exhibits uniform dissolution of the surface. The formation of the dense corrosion products leads to the improvement of overall corrosion performance. It indicates that the SNC-treated Cu-Mg alloy can function reliably for a longer duration in a corrosive environment.

Corrosion-Induced Mass Loss of Cu9Al4 at the Cu-Al Ball–Bond Interface: Explained Based on Full Immersion of Cu, Al, and Cu-Al Intermetallic Galvanic Couples

The disappearance of Cu9Al4 has been observed at the failed Cu-Al ball–bond interface in the standard humidity reliability test. Galvanic corrosion has been considered as the cause of the bond failure, yet no convincing argument has been provided to explain the preferential attack on Cu9Al4. Due to encapsulation, corrosion should proceed with the thin-layer electrolyte condition. The high ohmic resistance may constrain the galvanic corrosion between adjacent entities only. Thus, in this study, the galvanic corrosion between Cu and Cu9Al4, Cu9Al4 and CuAl2, and CuAl2 and Al were investigated using the zero-resistance ammetry. The results showed that the galvanic corrosion rate was the highest for the Cu9Al4-CuAl2 couple as compared with the other two galvanic couples. Also, the observed residual alumina between Cu9Al4 and CuAl2 and the associated internal stress build-up during the CuAl2-to-Cu9Al4 transition contributed to a higher crack propagation rate. Therefore, the failure first occurs at this interface. This failure then leads to a separation of Cu and Cu9Al4 from CuAl2 and Al. For the Cu-Cu9Al4 couple, Cu9Al4, the anode should corrode significantly faster due to the strong galvanic effect imposed by a larger surface area of Cu. In contrast, for the CuAl2-Al couple, the anodic corrosion rate of Al is slow as the galvanic effect imposed by the CuAl2 cathode is weak due to the small cathode surface area. As a result, Cu9Al4 disappeared from the failed ball–bond interface.

Effect of sintering atmosphere on corrosion resistance of NiFe2O4 ceramic in Na3AlF6–Al2O3 melt

A comparative study on the corrosion resistance of NiFe2O4 ceramic inert anode for aluminum electrolysis prepared in the different sintering atmosphere was carried out in Na3AlF6–Al2O3 melt. The results show that the corrosion rates of NiFe2O4 ceramic inert anodes prepared in the vacuum and the atmosphere with oxygen content of 1×10–2 are 6.08 cm/a and 2.59 cm/a, respectively. A densification layer is formed at the surface of anode due to some reactions which produce aluminates. For the anode prepared in the atmosphere with oxygen content of 1×10–2, the thickness of the densification layer (about 50 μm) is thicker than that (about 20 μm) formed at the surface of anode prepared in the vacuum. The content of NiO and Fe(II) in Ni(II) x Fe(II)1–x Fe(III)2O4 increases with the decrease of the oxygen content of sintering atmosphere, which reduces the corrosion resistance of the material.

Effect of halides in the electrowinning of zinc. II. Corrosion of lead-silver anodes

This paper summarizes experimental results obtained from a series of laboratory scale electrowinning tests conducted over 5months to quantify the effects of halides (chloride, fluoride and bromide) on the performance and corrosion of lead-silver anodes under conditions similar to those used during the electrowinning of zinc. The parameters investigated include operating anode potential, corrosion rate and anode scale/cell mud generation rates. Information was also obtained on the consumption of halides and manganese ions and the composition of the anode scale and cell mud.The results have confirmed plant observations of excessive anode corrosion and chlorine emissions at a chloride concentration of 400mg/L but not at a concentration of 200mg/L. It has also confirmed the importance of maintaining a suitable manganese(II) concentration in the electrolyte. Bromide and fluoride ions, albeit at lower concentrations, do not have measurable effects on anode corrosion.Although a definitive explanation for enhanced local corrosion at high chloride concentrations has not been advanced, the nature of the accelerated corrosion suggests that a crevice-like corrosion process is responsible for localized massive corrosion. This has been attributed to the presence of high acidity and permanganate ions between the manganese oxide layer and the alloy surface.

An effective hybrid organic/inorganic inhibitor for alkaline aluminum-air fuel cells

An issue associated with aluminum-based batteries is the drastic parasitic corrosion of aluminum anode, which significantly restricts the utilization of aluminum. An effective approach is to add inhibitors in electrolytes to reduce the anode corrosion rate. In this work, Na2SnO3 and casein are proposed to act as a hybrid inhibitor in alkaline aluminum-air fuel cell. It is demonstrated that 0.05M Na2SnO3 and 0.6gL−1 casein offers the strongest corrosion protection, reducing the corrosion rate by approximately one order of magnitude. The corrosion inhibition is mainly attributed to the inhibition of cathodic reaction process. In addition, the analysis on the morphology and composition of the aluminum surface suggests that casein can greatly promote the deposition of tin to form a uniform and stable layer on the aluminum surface, due to the strong adsorption of polar functional groups in casein. Furthermore, the use of the hybrid inhibitor in aluminum-air fuel cell contributes to an increase of discharge capacity by 89.3%.

Review—SEI: Past, Present and Future

The Solid-Electrolyte-Interphase (SEI) model for non-aqueous alkali-metal batteries constitutes a paradigm change in the understanding of lithium batteries and has thus enabled the development of safer, durable, higher-power and lower-cost lithium batteries for portable and EV applications. Prior to the publication of the SEI model (1979), researchers used the Butler-Volmer equation, in which a direct electron transfer from the electrode to lithium cations in the solution is assumed. The SEI model proved that this is a mistaken concept and that, in practice, the transfer of electrons from the electrode to the solution in a lithium battery, must be prevented, since it will result in fast self-discharge of the active materials and poor battery performance. This model provides [E. Peled, in “Lithium Batteries,” J.P. Gabano (ed), Academic Press, (1983), E. Peled, J. Electrochem. Soc., 126, 2047 (1979).] new equations for: electrode kinetics (io and b), anode corrosion, SEI resistivity and growth rate and irreversible capacity loss of lithium-ion batteries. This model became a cornerstone in the science and technology of lithium batteries. This paper reviews the past, present and the future of SEI batteries.

Effect of sintering atmosphere on corrosion resistance of Ni/(NiFe2O4–10NiO) cermet inert anode for aluminum electrolysis

A comparative study on the corrosion resistance of 17Ni/(NiFe2O4–10NiO) cermet inert anode prepared in different sintering atmospheres was conducted in Na3AlF6–Al2O3 melt. The results indicate that the corrosion rates of NiFe2O4-based cermet anodes prepared in the vacuum and the atmosphere with oxygen content of 2×10−3 (volume fraction) are 6.46 and 2.71 cm/a, respectively. Though there is a transition layer with lots of holes or pores, a densified layer is formed on the surface of anode due to some reactions producing aluminates. For the anode prepared in the atmosphere with oxygen content of 2×10−3, the thickness of the densification layer (about 50 μm) is thicker than that (about 30 μm) formed on the surface of anode prepared in the vacuum. The contents of NiO and Fe(II) in NiFe2xO4–y–z increase with the decrease of oxygen content in sintering atmosphere, which reduces the corrosion resistance of the material.

Observation of electrochemical reactions at Zn electrodes in Zn-air secondary batteries

The anode is the compartment for energy storage in Zn-air secondary batteries. In contrast, the cathode has no storage material but catalyzes the conversion of oxygen to hydroxide and vice versa. Because the composition of the anode varies with the state of charge, the potential of the battery reflects the composition of the materials in the anode. H2 evolution, corrosion, and zincate/ZnO formation occur at the anode during battery operation and have a negative effect on battery performance. Consequently, reducing these adverse reactions by manipulating one of the reaction parameters, such as the concentration of OH−, can improve performance. In addition, the influence of KOH concentrations ranging from 2.0 to 8.0M on these reactions is studied. We found that 4.0M KOH is the optimum concentration for both redox reactions (Zn2+/Zn) and suppression of the anode corrosion rate. However, the higher conductivity obtained with 6.0M KOH is appropriate when a faster reaction is needed, including suppression of negative effects. In particular, suppression of ZnO formation is advantageous, decreasing both resistance and H2 evolution in the cell.

Performance indicator of the atmospheric corrosion monitor and concrete corrosion sensors in Kuwait field research station

Two field research stations based upon atmospheric corrosivity monitoring combined with reinforced concrete corrosion rate sensors have been established in Kuwait. This was established for the purpose of remote monitoring of building materials performance for concrete under Kuwait atmospheric environment. The two field research sites for concrete have been based upon an outcome from a research investigation intended for monitoring the atmospheric corrosivity from weathering station distributed in eight areas, and in different regions in Kuwait. Data on corrosivity measurements are essential for the development of specification of an optimized corrosion resistance system for reinforced concrete manufactured products. This study aims to optimize, characterize, and utilize long-term concrete structural health monitoring through on line corrosion measurement and to determine the feasibility and viability of the integrated anode ladder corrosion sensors embedded in concrete. The atmospheric corrosivity categories supported with GSM remote data acquisition system from eight corrosion monitoring stations at different regions in Kuwait are being classified according to standard ISO 9223. The two nominated field sites where based upon time of wetness and bimetallic corrosion rate from atmospheric data where metals and rebar's concrete are likely to be used. Eight concrete blocks with embeddable anodic ladder corrosion sensors were placed in the atmospheric zone adjacent to the sea shore at KISR site. The anodic ladder corrosion rate sensors for concrete were installed to provide an early warning system on prediction of the corrosion propagation and on developing new insights on the long-term durability performance and repair of concrete structures to lower labor cost. The results show the atmospheric corrosivity data of the environment and the feasibility of data retrieval of the corrosion potential of concrete from the embeddable sets of anodic ladder corrosion sensors.

The Influence of Temperature and Composition on the Operation of Al Anodes for Aluminum‐Air Batteries

AbstractThe influence of composition and temperature on the anode polarization and corrosion rate of pure Al and Al‐In anodic alloys in 8M NaON electrolyte has been investigated. High current density (more than 800 mA cm−2) and faradaic efficiency over 97% were observed for all investigated alloys at 60 °C. Lower temperature provides lower current density (200–300 mA cm−2 at 40 °C, and less than 100 mA cm−2 at 25 °C). Different formation of the product reaction layers was observed for pure aluminum and Al–0.41In alloy, leading to the different polarization character of the samples.The comparison of two Al‐In alloys with similar composition has been carried out. Al–0.45In alloy having a coarse‐grained structure had a more positive no‐current potential and lower value of anode limiting current (200 mA cm−2 vs. 300 mA cm−2) compared with the fine‐grained Al–0.41In alloy, as well as greater parasitic corrosion rate and greater no‐current corrosion.The current‐voltage, power and discharge characteristics of the aluminum‐air cell with Al–0.41In anode and gas diffusion cathode have been investigated. Open circuit voltage of the cell is 1.934 V and the maximum power density of the cell is 240 mW cm−2 at the voltage of 1.3 V.

Comparative study of the effect of lanthanum and scandium additives on anodic characteristics of AK1 alloy based on special-purity aluminum

Potentiostatic method was used to study the corrosion-electrochemical properties in a 3% NaCl electrolyte of an AK1 alloy modified with lanthanum and scandium. It was found that the lanthanum and scandium additives positively affect the corrosion resistance of the AK1 alloy in the NaCl electrolyte. For example, the additives reduce the anodic corrosion rate of the alloy by 3.6 × 10–4 to 0.97 × 10–4 g m–2 h–1. Upon alloying of the alloy, the pitting and corrosion potentials are shifted into the positive region, which indicates that alloys containing lanthanum and scandium become more pitting corrosion resistant.

Effects of copper and titanium on the corrosion behavior of newly fabricated nanocrystalline aluminum in natural seawater

Fabrication of a newly nanocrystalline Al and two of its alloys, namely Al–10%Cu; and Al–10%Cu–5%Ti has been carried out using mechanical alloying (MA) technique. The corrosion behavior of these materials in aerated stagnant Arabian Gulf seawater (AGSW) at room temperature has been reported. Cyclic potentiodynamic polarization (CPP), chronoamperometric current-time (CCT) and electrochemical impedance spectroscopy (EIS) measurements along with scanning electron microscopy (SEM) and X-ray energy dispersive (EDX) investigations were employed to report the corrosion behavior of the fabricated materials. All results indicated that Al suffers both uniform and localized corrosion in the AGSW test solution. The presence of 10%Cu decreases the corrosion current density, the anodic and cathodic currents and corrosion rate and increases the corrosion resistance of Al. The addition of 5%Ti to the Al–10%Cu alloy produced further decreases in the corrosion parameters. Measurements together confirmed that the corrosion of the fabricated materials in AGSW decreases in the order Al>Al–10%Cu>Al–10%Cu–5%Ti.

Anticorrosion efficiency of ultrasonically deposited silica coatings on titanium

We utilized high intensity ultrasound to prepare coatings of silica and organically modified silica composed of multiple layers of densely packed nanoparticles. Ultrasound was used to collide nanoparticles onto an activated titanium surface with high speed. Large areas could be homogeneously coated by this method. These coatings were characterized by spectroscopy and microscopy methods and the anticorrosion efficiency in NaCl solution was evaluated by electrochemical measurements. The results indicated that the composite coatings provided good quality barrier layer on bare titanium and decreased the anodic corrosion rate. It was found that increase in the organic content of the coating shifted the passivation potential towards more positive direction. The comparison of the impedance results recorded at the corrosion potential pointed out that in each case a good quality barrier layer was formed on the titanium surface. The outstanding corrosion resistance of the composite coatings with only ~200nm thickness shows that ultrasound assisted deposition can be a competitive method to obtain corrosion protective layers.

Electrochemical investigations on the corrosion inhibition of aluminum by 3-amino-1,2,4-triazole-5-thiol in naturally aerated stagnant seawater

The corrosion behavior of aluminum and its inhibition by 3-amino-1,2,4-triazole-5-thiol (ATAT) in naturally aerated stagnant Arabian Gulf water was reported. The work was carried out using electrochemical impedance spectroscopy (EIS), cyclic potentiodynamic polarization (CPP), and potentiostatic current–time (CCT) measurements. EIS data indicated that ATAT decreased the corrosion of Al by increasing the solution and polarization resistances, the impedance of the interface and the maximum degree of phase angle. ATAT was also found to decrease the cathodic, anodic, and corrosion currents and corrosion rate as well as increase the polarization resistance of Al as confirmed by the CPP and CCT measurements.

Non-mechanical behaviors of soft clay in two-dimensional electro-osmotic consolidation

To investigate the soil behaviors in a direct current field on both spatial and temporal scales, a 1: 5 scale model test was conducted in laboratory to simulate the two-dimensional (2D) electro-osmotic consolidation of soft clay foundation. Volume of drainage, intensity, voltage, water content and pH value of water collected in the cathodes were monitored. The pH values of soil and the mass of anodes were measured before and after the test. The test results indicate that the unsaturated state, resultant from fissures induced by the differences in water contents, is favorable to dynamic compaction of soil during electro-osmotic drainage. The results also demonstrate that water content, degree of saturation and electric potential distributions can be used to deduce the electro-osmotic drainage process. Water content of soil decreases first near electrodes, while keeps nearly constant in the center of the model. The area with constant water content is larger than half of the sample surface. Moving anodes towards cathodes by about one third of the electrode spacing is effective to improve the treatment effect after electro-osmosis stops due to the large resistance. Moreover, it is observed that during electro-osmosis, the corrosion rate of anodes becomes smaller, while the variation in pH values of soil near anodes becomes larger.