Aluminium Sacrificial Anode Research Articles

Development of Al-Mg Alloy for the Protection of Steel Structure in 3.5% Nacl

Aluminium (Al) is thoroughly used as a sacrificial metal for the protection of steel in seawater. Aluminium is rarely used as a sacrificial anode without being alloyed due to its built-in properties to get passivates and form a passive layer and the continuity of its layer depends on the chemical composition and microstructure. In this paper, Aluminium-Magnesium(5xxx) system is considered because magnesium remarkably affects the chemical properties by changing the microstructure of Aluminium from a homogeneous solid solution to a complex structure with multiple intermetallic phases. In this research work developing Aluminium-Magnesium alloys containing 2.5 and 4.5 weight percent magnesium. The microstructures of pure aluminium and developed alloys were studied and the effect of the distribution of magnesium whether as a second phase particle, intermetallic compound or precipitates on the performance of aluminium sacrificial anode was discussed. Standard weight loss method and potentiodynamic tests are used to evaluate the performance of alloy sacrificial anode. The result shows that as the magnesium content increases corrosion rate of developed alloy increases and corrosion potential shifts in more negative directions. Corrosion potential is increased by 250 mV at 4.5% magnesium because of the formation of an intermetallic compound of aluminium& Magnesium (β phase - Al3Mg2) at the grain boundary. Magnesium improves the corrosion rate of developed alloy,it acts as a depassivators for the passive film of Aluminium by forming intermetallic compound and this compound has different electrochemical properties that leads to corrosion of aluminium and improves the performance of aluminium sacrificial anode.

Artificial neural network modelling to predict the efficiency of aluminium sacrificial anode

ABSTRACT Study explores the potential of a deep learning-based approach for predicting the current efficiency of aluminium sacrificial anodes in marine environments. The model takes into account various input variables, including the chemical composition of the sacrificial anode, pH, dissolved oxygen (DO), temperature, pressure, cathode electrode, current density, and the ratio of the surface area of the cathode to anode, with the anode current efficiency serving as the output variable. Utilising artificial neural networks in this study shows a mean absolute percentage error of 6.4% and 7.8% for the training and validation for predicting the current efficiency. The proposed model shows promising potential to predict the current efficiency of aluminium sacrificial anodes and improve the design of cathodic protection systems based on aluminium sacrificial anodes.

Effect of backfilled stone/brine media on the long‐term free corrosion and electrochemical performance of an aluminum sacrificial anode

AbstractAn Al–Zn–In–Si–Sn–Ti sacrificial anode, utilized to protect steel shells of subsea‐immersed tunnels, works in a backfilled stone (6–10 mm)/brine (40 Ω cm) media (125 Ω cm). This paper investigated its impact on the anode's long‐term free corrosion and electrochemical performance. After prolonged free corrosion, the anode's general corrosion rate is minimal. Although its capacity (Q) and current efficiency (η) increase slightly, it shows a nonuniform dissolution state. Over a long‐term working period, a significant amount of Al(OH)3 deposits and diffuses between the backfilled stone toward the cathode surface, creating distinct stone impressions and a thick product layer. These effects considerably increase the media ρ around the anode and continuously decrease the brine's pH, decreasing Q and η values and output currents. Nonetheless, the current distribution within the media gradually becomes uniform with time, resulting in a homogeneous potential distribution along the cathode.

Effect of backfilled stone/brine media on the initial electrochemical performance of aluminum sacrificial anode

AbstractAluminum alloy sacrificial anodes applied to protect the subsea immersed tunnels' steel shells are buried in an unfamiliar inhomogeneous backfilled stone/brine media. To verify its influence, the effect of the backfilled stone (10–12, 6–10, and 3–6 mm)/brine (40 Ω cm) media, denoted as Stone 1, Stone 2, and Stone 3, on the initial electrochemical performance of an Al─Zn─In─Si─Sn─Ti anode is investigated by electrochemical and surface analysis techniques. With decreasing the stone size, the Stones 1–3 media's resistivity increases to 100, 125, and 150 Ω cm, respectively. The backfilled stone/brine media inhibits the anode′s free corrosion and pitting process and accelerates its activation in the initial period. The anode′s capacity and current efficiency decrease slightly; however, the anode′s output current and its transmission are depressed more heavily by decreasing the backfilled stone size. Also, the backfilled stone shields parts of the cathode surfaces, decreases dissolved oxygen concentration, and blocks the diffusion of the anode's dissolution product in the media, resulting in the change of the anode's protective effect.

Development of metal oxide incorporated Al-Zn-Sn sacrificial anodes processed by stir casting and heat treatment

Aluminum sacrificial anodes are currently the first choice for cathodic protection in numerous applications. The galvanic performance of aluminum-based sacrificial anodes is considerably enhanced by addition of certain alloying elements called activators. Recent researches proved that incorporation of specific metal oxides like MnO2, CeO2, RuO2, and IrO2 into the aluminum matrix could enhance the galvanic efficiency of aluminum anodes; however, the mechanism by which metal oxides improve galvanic properties of aluminum is still subject to discussion. The present work investigates the effect of incorporating commercially available low-cost manganese dioxide concentrate into Al-5Zn-0.1Sn sacrificial anodes in different volume fractions. It also studies the influence of heat treatment on anode’s galvanic performance by performing solution treatment at 3 different temperatures (250 °C, 400 °C, 550 °C). The electrochemical testing results proved an increase in efficiency of anodes incorporated with metal oxides and solution treated at 550 °C. The SEM imaging and EDX elemental mapping declared that the presence of SiO2 particles in the anode matrix which might cause effective and uniform corrosion of Al anodes and decreased non-coulombic losses.Graphical abstract

High-Productivity Single-Pass Electrochemical Birch Reduction of Naphthalenes in a Continuous Flow Electrochemical Taylor Vortex Reactor.

We report the development of a single-pass electrochemical Birch reduction carried out in a small footprint electrochemical Taylor vortex reactor with projected productivities of >80 g day–1 (based on 32.2 mmol h–1), using a modified version of our previously reported reactor [Org. Process Res. Dev.2021, 25, 7, 1619–1627], consisting of a static outer electrode and a rapidly rotating cylindrical inner electrode. In this study, we used an aluminum tube as the sacrificial outer electrode and stainless steel as the rotating inner electrode. We have established the viability of using a sacrificial aluminum anode for the electrochemical reduction of naphthalene, and by varying the current, we can switch between high selectivity (>90%) for either the single ring reduction or double ring reduction with >80 g day–1 projected productivity for either product. The concentration of LiBr in solution changes the fluid dynamics of the reaction mixture investigated by computational fluid dynamics, and this affects equilibration time, monitored using Fourier transform infrared spectroscopy. We show that the concentrations of electrolyte (LiBr) and proton source (dimethylurea) can be reduced while maintaining high reaction efficiency. We also report the reduction of 1-aminonaphthalene, which has been used as a precursor to the API Ropinirole. We find that our methodology produces the corresponding dihydronaphthalene with excellent selectivity and 88% isolated yield in an uninterrupted run of >8 h with a projected productivity of >100 g day–1.

Evaluating the Performance of Aluminum Sacrificial Anodes with Different Concentration of Gallium in Artificial Sea Water

In this manuscript, the influence of gallium content additions of Al-Zn-In-Mg alloy was investigated through electrochemical techniques and microstructure observation in 3.5 wt% NaCl solution. The results indicated that Al-Zn-In-Mg-0.03Ga alloy has the best discharge performance among all alloys. We propose that this is due to the fact that gallium addition to the Al-4Zn-In-Mg alloy improves the discharge activity of the alloy as well as elevating its anodic efficiency. In particular, the effect of gallium addition to improve discharge activity tends to be a parabolic curve, in which there is an increase when the gallium is first added that rises to the maximum anode current efficiency of about 98.25% whenever gallium content is 0.03 wt%.

Abatement of As and hydrated silica from natural groundwater by electrocoagulation in a continuous plant having an electrolyzer and a flocculator-settler

• As and hydrated silica elimination from deep well water by electrocoagulation (EC). • Aluminum sacrificial anodes in an EC reactor coupled to a flocculator-settler. • Aluminum and hydrated silica react, forming aluminosilicates, As adsorbs on flocs. • As concentration after EC treatment met the WHO guideline, hydrated silica is abated. • EC is a cheap (0.48 USD m −3 ) and accessible technology to treat natural groundwater. This paper shows the elimination of arsenic (As) and hydrated silica from natural groundwater (48.63 µg L −1 arsenic, 77.5 mg L −1 hydrated silica, 0.33 mg L −1 phosphate, 5 mg L −1 sulfate, 240 mg L −1 alkalinity, 89.5 mg L −1 hardness, pH 8.44 and 450 µS cm −1 conductivity) by electrocoagulation (EC). The flow plant employed a parallel plates EC reactor in series with a flocculator-settler. Aluminum was used as the sacrificial electrode. Before the electrolysis in the flow plant, a systematic study of the aluminum dose was carried using the EC reactor adapted to a jar test. The influence of the mean linear flow velocity (1.2–4.8 cm s −1 ) and current density (6–9 mA cm −2 ) on the removal of As and hydrated silica was addressed. The residual concentration of As and hydrated silica in the flow plant was C As = 4.2 µg L −1 and C hs = 4.5 mg L −1 , respectively, at 9 mA cm −2 and 1.2 cm s −1 , which agree well with that obtained in the jar test array. The residual As concentration fulfills the World Health Organization (WHO) recommendation (<10 μg L −1 ). The total operating cost of EC was 0.48 USD m −3 , considering electrolytic energy consumption, aluminum price, pumping costs, and sludge confinement. Flocs analyses performed by SEM-EDS, XRF-EDS, XRD, and FTIR showed the existence of aluminosilicates formed by the reaction of aluminum and hydrated silica. At the same time, As, phosphates and sulfates were separated by adsorption on flocs.

AC Corrosion behaviour of aluminium and zinc sacrificial anodes in seawater

ABSTRACT In this work, the corrosion behaviour of aluminium (Al) and zinc (Zn) sacrificial anodes under AC interference were studied in 3.5% NaCl solution by AC corrosion simulation experiments, weight loss tests and surface morphology analyses. It was found that AC accelerated the corrosion of Al and Zn, and their corrosion rates increased with the AC current density, besides the localised corrosion of Al was much more obvious than Zn. When the AC current density was 100 A m−2, the uniform corrosion rates of Al and Zn increased to 14.6 and 0.46 mm/year, respectively, which were 34.8 and 1.48 times of the free-corrosion rates of them. Meanwhile, both the uniform and localised corrosion rates of Al increased much more significant than that of Zn under AC interference.

Influence of silicon on the corrosion behavior of Al–Zn–In sacrificial anode

Steel structures used in offshore sectors are often exposed to adverse weather conditions, and thus, require the application of efficient and safe corrosion protection techniques. The application of sacrificial anodes with aluminum alloys for cathodic protection is a viable anticorrosive protection alternative for long-term wet conditions owing to its low density, galvanic economy, better performance, availability, and recyclability. This study aims to evaluate the effect of different percentages of silicon in commercial Al–Zn–In alloys, used in aluminum sacrificial anodes, on the electrochemical properties of the alloys. The DNV-RP-B401 standard was used to analyze the electrochemical performance and manufacturing of commercial matrix alloys according to the prescribed chemical composition. They were characterized by optical emission spectrometry, electrochemical performance, electrochemical polarization assay, macrography, and scanning electron microscopy. The results revealed greater work efficiency and corrosion uniformity for aluminum cathodic protection anodes with the addition of 0.10% by weight of silicon, which resulted in disk shape precipitation and reduced grain size and smaller spacing between dendritic arms. Therefore, with this percentage of silicon, the anodes exhibit less automatic corrosion of the anode mass, that is, greater anticorrosive protection, smaller amounts of corrosion residues in the medium, less anode disposal with exhausted life, and greater application sustainability for the aluminum anode.

Optimization of Stir Casting Process Parameters for Producing MMC Aluminum Sacrificial Anode Incorporated with Manganese Dioxide Concentrate Powder

Optimization of Stir Casting Process Parameters for Producing MMC Aluminum Sacrificial Anode Incorporated with Manganese Dioxide Concentrate Powder

Electrochemical Degradation of Industrial Dyes in Wastewater through the Dissolution of Aluminum Sacrificial Anode of Cu/Al Macro-Corrosion Galvanic Cell.

This paper reports on the process of industrial-type wastewater purification carried-out through continuous anodic dissolution of aluminum alloy sacrificial anode for artificially aerated Cu-Al alloy galvanic (macro-corrosion) cells and synthetically prepared wastewater solutions. Electrochemical experiments were performed by means of a laboratory size electrolyzer unit, where the electrocoagulation process along with surface-induced electrooxidation phenomena were examined for wastewater containing Acid Mixture and Disperse Red 167 dyes. Final reduction of the dyes concentrations came to 32 and 99% for Acid Mixture and Disperse Red 167, correspondingly. The above was visualized through the employment of electrochemical (cyclic voltammetry and a.c. impedance spectroscopy techniques) and instrumental spectroscopy analyses.

Effects of Alloying with Sn and Mg on the Microstructure and Electrochemical Behavior of Cast Aluminum Sacrificial Anodes

The influence of alloying with Sn and Mg instead of In during casting of Al–5 wt% Zn sacrificial anodes on their microstructure and electrochemical properties was investigated. The addition levels were 0.1–1.0 wt% Sn and 0.5–2.0 wt% Mg. The different microstructures were studied, and the effect of particles distribution on the performance of the alloys as sacrificial anodes was discussed. It was observed that increasing amount of Sn distributes its particles locally on the grain boundaries which remarkably affected the electrochemical behavior of the alloys. Adding Sn up to 1.0% gradually shifted the potential of the Al–5 wt% Zn alloy toward more negative values (~ − 0.92 to − 1.1 V) and enhanced the breakdown of the oxide layer. Accordingly, the alloys containing Sn in amounts that range between 0.3 and 1.0 wt% exhibited electrochemical properties close to that of the In-containing alloy. Magnesium addition of 0.5 wt% showed remarkable grain refinement where the grain size range of the base alloy was reduced from (150–200 μm) down to (70–100 μm) due to Mg distribution on the grain boundary area. With increasing Mg wt%, grain coarsening occurred due to the segregation of Mg in the matrix which encouraged the breakdown of the passive film and hence increased the corrosion rate. However, the potential levels of the investigated Mg alloys showed more positive values compared to that of the In-containing alloy, which may hinder using this group of alloys for sacrificial anodes applications.

Environmental Impact Assessment of Sacrificial Anode Method in Taiwan Strait

Taiwan Strait is one of the potential wind farm in the world. Cooperate with the development of national policies, thousands of offshore wind turbines will be installed in Taiwan Strait. In order to enable offshore wind turbine foundation to be erected in the ocean for a long time, the offshore structure facilities are protected by sacrificial anode or impressed current of today. This study utilized the MIKE21 numerical model, combined with ocean parameters such as sea waves and tidal current to simulate the change of the diffusion concentration and diffusion range of the materials released by the aluminum sacrificial anode blocks by the Changhua offshore wind farm located on Taiwan Strait in winter and summer, thus to evaluate the impact on the marine environment.

Study of Al-Zn-Cu-Sm Efficiency for Low-Voltage Sacrificial Anode Candidate

Sacrificial anode is one of the most effective methods for preventing corrosion in seawater environment. Aluminum (Al) anode works very well in seawater environment with high electrochemical capacity and high driving voltage. Commonly used aluminum alloy sacrificial anodes have the possibilities to trigger the occurrence of Stress Corrosion Cracking and Hydrogen Embrittlement due to overprotection on high-strength steel. The low voltage sacrificial anode was developed to overcome this problem. Electrochemical behavior of Al-5Zn-0.5Cu alloy with varied samarium (Sm) addition of 0.02 wt% and 0.1 wt% was investigated in this study. The commonly used Al-5Zn-0.02In alloy is also tested as a comparison. Anode efficiency test with weight loss method according to DNVGL-RP-B401 standard was conducted to determine the performance of Al-5Zn-0.5Cu-xSm alloy. The addition of 0.1 wt% Samarium shows the best anode performance with electrochemical capacity 2809.80 Ah/kg and 98% efficiency. Al-5Zn-0.5Cu-0.1Sm alloy is the most potential alloy to be developed as a low potential sacrificial anode to replace commonly used aluminum sacrificial anode with indium addition.

Efficiency and characterization study of low voltage current sacrificial anode on Al-Zn-Cu and Al-Zn-Si alloy

The sacrifice of the anode is the cathodic protection used to prevent corrosion. Al-Zn-In alloys are often used it causes excessive protection that can increase the possibility of hydrogen embrittlement in high-strength steel. Therefore, the solution is to use aluminum alloys with low voltage current. The purpose of this research is to know the efficiency of aluminum sacrificial anode with alloy elements Zn, Si and Cu as low voltage current. As well as studying the potential of Al alloys with elements Zn, Cu and Si can be used as sacrificial anodes at sea water conditions. Testing methods performed are Optical Emission Spectroscopy testing, weight loss testing, efficiency testing, Electrochemical Impedance Spectroscopy testing, and metallographic testing. From this research, we found the result of Al-Zn-Cu alloy which has electrochemical capacity and best efficiency is Al-5Zn-0,1Cu Alloy for 2795 Ah / kg with 98% efficiency and Al-Zn-Si alloy with capacity value electrochemistry and the best efficiency is Al-5Zn-0.1Si alloy for 2808 Ah / kg with 98% efficiency. The lowest value of transfer resistance is found in Al-5Zn-0.1Cu alloy and Al-5Zn-0.1Si alloy with the value of 1012.7 Ω and 1092.9 Ω and the double capacitance value in the smallest Al-Zn-Cu alloy is alloy Al-5Zn-0.5Cu with the value of 13.2 μMho while in Al-Zn-Si alloys are present in Al-5Zn-0.5Si with the value of 19 μMho. With the structure obtained is the greater the addition of Cu and Si, the more rough and corroded surface sacrificial anodes.

ACA/BEM for solving large-scale cathodic protection problems

Cathodic protection (CP) techniques are widely used to avoid corrosion sequences in offshore structures. Boundary Element Method (BEM) is an ideal method for solving such problems since it requires only the meshing of the boundary and not the whole domain of the electrolyte as Finite Element Method does. This advantage becomes more pronounced in CP systems where electrochemical reactions occur mainly on the surface of the metallic structure. In the present work, an accelerated BEM enhanced by Hierarchical Matrices and Adaptive Cross Approximation techniques (ACA) is proposed for the solution of large-scale 3-D CP problems. An offshore oil steel platform, galvanically protected by a number of aluminum sacrificial anodes, is analyzed by means of the proposed ACA/BEM. The nonlinear polarization curves for steel and aluminum in seawater are employed to facilitate the boundary conditions. The potential, as well as, the current density are effectively evaluated and presented.

Evaluating the performance of zinc and aluminum sacrificial anodes in artificial seawater

The cathodic protection of the metallic structure buried/immersed in the aggressive media depends on the electrochemical properties of the sacrificial anode. The objective of this work is to evaluate the performance of the sacrificial anodes i.e. aluminum and zinc alloys developed in our laboratory. The microstructural analysis of the aluminum and zinc anodes revealed the formation of pure α and η phases, respectively. However, in Al few precipitates were accumulated along the grain boundaries of α phase whereas the typical intragranular twin bands and dendrite structure was evident in the case of Zn anode. The performance of the anode materials was evaluated according to the standard test procedure (TM0190) as recommended by NACE. The mass loss and hydrogen evolution tests were conducted to determine the current efficiency of these sacrificial anode materials in artificial seawater. The current efficiency of the aluminum and zinc anode from the mass loss measurement was measured to be 93.3 and 66.6%, respectively. The anode capacity of Al and Zn was 2784.8 and 519.36 A h kg−1 which was high as reported earlier. However, according to the hydrogen evolution test, the current efficiency was 86.2 and 95.3% for aluminum and zinc anodes, respectively. The open circuit potential of both anodes was also shifted to more negative potential (active state) within 336 h exposure to artificial sea water.

Optimization of batch electrocoagulation process using Box-Behnken experimental design for the treatment of crude vegetable oil refinery wastewater

The performance of the batch electrocoagulation process for the treatment of real crude vegetable oil refinery wastewater with high COD using sacrificial aluminum anode was explored in this research. Effects of operating factors such as electrolysis time (0–60 min), applied voltage (10–20 V) and electrode spacing (2–4 cm) on the COD removal were investigated. Mathematical model relating these key operating factors and the COD removal was developed using Box-Behnken design. 3-D response surface plots showed that the COD removal significantly increased with increase in electrolysis time and applied voltage till the optimum value. COD removal decreased, when very short or excessive electrode spacing was fixed. Experimental COD removal of 70.8% was attained at the optimized conditions and observed to be in reasonable agreement with the prediction by the Box-Behnken design.

An energy-efficient air-breathing cathode electrocoagulation approach for the treatment of arsenite in aquatic systems

An air-breathing cathode electrocoagulation (ACEC) process with a sacrificial aluminum anode was used to treat arsenite (As(III)) from aqueous systems. Its performance was investigated by controlling operational parameters. As(III) removal efficiency of the ACEC increased from 81 to 86% with an increase in NaCl concentration from 10 to 20mM. Furthermore, we were able to observe the oxidation of As(III) into its corresponding ions as well as the production of an aluminum oxide hydroxide in the form of boehmite. This study describes ACEC as one of the most energy-efficient treatment methods for As(III) removal based on its performance evaluation.