Aluminium Sacrificial Anode Research Articles

Reducing the cost of ballast tank corrosion: an economic modeling approach

One of the most relevant problems in ship construction and maintenance nowadays concerns the corrosion in the double hull space ballast tanks of modern merchant vessels. On the one hand, there is a general consensus that the economic life span of such a vessel depends primarily upon the corrosion state of its ballast tanks, while on the other hand, the position of these tanks, squeezed between the outer hull and the loading tanks, makes routine inspection and maintenance almost impossible.Today, ship's ballast tanks are usually constructed in grade A steel and protected with a standard epoxy coating, backed up with sacrificial zinc anodes. Such a construction has been applied without significant alterations for many years. However, the objective of this economic study is to compare this construction method with some feasible alternatives. The considered alternatives are: (1) an increase of the scantlings, eliminating the necessity to replace corroded steel but diminishing the cargo carrying capacity of the ship, (2) application of the novel and more durable TSCF25 coating (3), the use of corrosion resistant steel in ship construction or (4) a standard PSPC15 coating combined with lifetime lasting aluminum sacrificial anodes. After running each alternative through a cost model including an extensive sensitivity analysis, it is concluded that the durable coating and the use of lifetime lasting aluminum anodes are bound to improve the actual basic tank concept. Corrosion resistant steel becomes attractive depending upon the evolution of the international steel market.

Study on alternative approaches to corrosion protection of ballast tanks using an economic model

One of the most relevant problems in ship construction and maintenance nowadays is corrosion in ballast tanks of modern merchant vessels. On the one hand, there is a general consensus that the economic lifespan of such a vessel depends, to a large degree, upon the corrosion state of its ballast tanks, while on the other hand these ballast tanks, located between the outer hull and the cargo tanks, makes routine inspection and maintenance a difficult task.Today, ship's ballast tanks are usually constructed in steel and protected with an epoxy coating backed up by sacrificial zinc anodes. Such a construction has been applied without significant alterations for many years. The objective of this economic study is to compare this construction method with some potential alternatives. The considered alternatives are: (1) an increase in structural scantlings, eliminating the necessity to replace corroded at a cost of real cargo carrying capacity of the ship, (2) application of the novel and more durable TSCF25 coating (3), the use of corrosion resistant steel in ship construction and (4) a standard PSPC15 coating combined with lifetime lasting aluminum sacrificial anodes. A cost model was used to evaluate these alternative options together with sensitivity analysis. It is concluded that the durable coating and the use of lifetime lasting aluminum anodes are bound to improve the actual basic tank concept. Corrosion resistant steel becomes attractive when the steel price becomes competitive.

Mechanistic study of electrochemical treatment of basic green 4 dye with aluminum electrodes through zeta potential, TOC, COD and color measurements, and characterization of residues

Herein we report a study on the changes in zeta potential during the electrochemical (EC) treatment of basic green 4 (BG) dye solutions. BG is a basic acrylic dye with a triphenylmethane group. It is extensively used in the textile and other industries. This study was conducted in a batch electrochemical reactor using a sacrificial aluminum anode. Zeta potentials were measured with changes in operating variables such as current density (j), initial pH (pH0), and initial dye concentration (C0). The process performance was analyzed in terms of the chemical oxygen demand (COD), total organic carbon (TOC) and decolorization efficiency along with important cost-related parameters such as electrode and energy consumption. At the optimum conditions, 82.4% COD, 63.5% TOC and 99.4% color removal efficiencies were observed, when C0 = 100 mg L−1, the treatment time was 45 min, with j = 117.64 A m−2 and the initial pH0 = 6.2. The respective electrode and energy consumptions at the optimum conditions were 0.16 kg Al per kg COD removed and 2.48 kW h per kg COD removed. The magnitude of the zeta potential gave an indication regarding the potential stability of the colloidal suspensions of BG dye and aluminum flocs present in the solution over the pH range of 3.2–12.2. It was found that the removal of the cationic dye was maximum when the zeta potential was least negative and that the removal was due to adsorption on neutral aluminum hydroxide. Finally, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), pore size distribution and thermogravimetric analysis (TGA) techniques were used to characterize the solid residues obtained during the EC treatment of aqueous solutions with and without BG dye.

Electrochemical dicarboxylation of conjugated fatty acids as an efficient valorization of carbon dioxide

Carbon dioxide was electrochemically incorporated in internal conjugated dienes and the process was optimized to achieve satisfactory yields (>70%) even for less reactive substrates. Reactions were performed galvanostatically in an undivided cell at room temperature with a magnesium or aluminium sacrificial anode. Using an optimized electrosynthetic method for the dicarboxylation of 1,3-cyclohexadiene (optimal electrode material, CO2 pressure, amount of charge), the effect of molecular configuration and alkyl substitution on the reactivity of conjugated double bonds towards carboxylation was studied. Use of a bubble reactor at atmospheric pressure instead of a higher pressure reactor, and lowering of the current density made it possible to effectively perform the double carboxylation of internal conjugated double bonds in open chains. Conjugated linoleic acid methyl esters were used in this reaction for the first time and by searching for the optimal reaction conditions (solvent, supporting electrolyte, reactant concentration, amount of charge, current density) yields approaching 80% of the corresponding fatty triacid product could be obtained, at current efficiencies over 50%.

The impact of aluminium sacrificial anodes on the marine environment: A case study

Cathodic protection using Al sacrificial anodes is a method of corrosion control that is often applied to submerged metallic structures. This technique leads to the progressive dissolution of the sacrificial anode and the metal(s) constituting the anode are inevitably released into the surrounding aquatic environment with potentially detrimental effects. The chemistry of sediments and waters from a French harbour where Al sacrificial anodes are deployed is examined in this study. In order to assess the potential influence of Al dissolution from the anode on the aquatic environment, total Al concentrations in water and sediment were determined and corresponding Al enrichment factors were calculated. Single and sequential extractions were also undertaken in order to evaluate the mobility of Al in the sediments. Results showed that whilst anodic dissolution does not significantly increase the concentration of Al in the water, both enrichment and an increase in the mobility of Al were evident in sediments sampled from the vicinity of the sacrificial anodes.

Direct electrochemical reduction of organic halide droplets dispersed in water

The direct electroreductive homocoupling of benzyl bromide has been efficiently achieved using water as the solvent. This process does not involve any organic co-solvent, transition metal catalyst, oil, surfactants, but only a cheap and non-toxic supporting electrolyte (KCl). Benzyl bromide droplets dispersed in water were reduced at a low current density, in an undivided cell fitted with a sacrificial aluminum anode. Various cathode materials have been tested (Ni, Pt, C, Ag) to favor organic halide reduction versus hydrogen evolution. Moreover, it was shown that the presence of aluminum cations generated by the oxidation of the anode played a crucial role in the efficiency of the electrochemical reduction step. Surprisingly, this property was exalted in acidic solutions (pH = 1). Under such acidic conditions, both bibenzyl proportion and faradaic yields were considerably improved. The electrochemical activation of energetically stronger C–X bonds such as those encountered in benzyl chloride (Csp3–Cl) or ethyl 4-iodobenzoate (Csp2–I) could be also achieved in water though resulted in lower faradaic yields. From a mechanistic point of view, both the faradaic yields and the product distribution obtained under various conditions suggested the occurrence of a radical coupling pathway occurring within the organic droplets or at their surface.

Effect of segregation on initiation of corrosion of aluminium sacrificial anode containing mischmetal

The effects of rare earth (RE) elemental additions in the form of mischmetal, added into an Al–Zn–In sacrificial anode alloy, were studied in 3% NaCl solution. Scanning electron microscopy and energy dispersive X-ray analysis were employed to analyse the microstructure of all Al alloys. Potentiodynamic polarisation of the anode material and a model alloy that simulated the segregated grain boundary composition were also investigated. The results showed that the microstructure of Al–Zn–In–RE alloy exhibited a typical dentritic form with small precipitates in an Al matrix and eutectic in interdendritic regions. Preferential attack from anodic segregation produced the early pitting and minor element enrichment on the surface, thus activating the anodes. Thus, using a RE mischmetal, which is much cheaper than pure RE elements, Al–Zn–In–RE alloys obtained desirable electrochemical properties for Al sacrificial anodes.

Electroreduction of tetra-coordinate phosphonium derivatives; one-pot transformation of triphenylphosphine oxide into triphenylphosphine

Electroreduction of triphenylphosphine dichloride in acetonitrile was performed successfully in an undivided cell fitted with an aluminium sacrificial anode and a platinum cathode, wherein Al 3+, which was electrogenerated at the anode would react as a Lewis acid with triphenylphosphine dichloride to afford tetra-coordinate chlorotriphenylphosphonium species and subsequent two-electron reduction at the cathode would give triphenylphosphine. One-pot transformation of triphenylphosphine oxide to triphenylphosphine was achieved successfully by the treatment of triphenylphosphine oxide with oxalyl chloride and subsequent electroreduction. In a similar manner, some tetra-coordinate triphenylphosphonium species derived from triphenylphosphine oxide were reduced electrochemically to triphenylphosphine in moderate yields.

Influence of Si on the Electrochemical Performance of Al-Zn-In-Mg-Ti Sacrificial Anode Alloy

The effects of Si content on the electrochemical performance of Al-5Zn-0.03In-1Mg- 0.05Ti (wt.%) alloy were studied by the electrochemical measurements and metallographic method. The optimal microstructures and electrochemical performance were obtained when the Si content in Al-Zn-In-Mg-Ti alloy was 0.1 wt.%. This anode alloy shows a current efficiency of 94.3% with even corrosion. However, in the case of Si content over 0.1 wt.%, the electrochemical performance of aluminum sacrificial anode shows only a nil improvement, and the corrosion morphology becomes uneven. The results reveal that the appropriate amount of Si is effective on reducing the harmful effect of iron impurities, improving the non-uniform corrosion and the electrochemistry performance of Al-Zn-In-Mg-Ti alloy.

Influence of fouling on the efficiency of sacrificial anodes in providing cathodic protection in Southeast Asian tropical seawater

Aluminum and zinc based sacrificial anodes are routinely used to provide corrosion protection to metals (typically steel) exposed to seawater, for example in steel pipelines and storage tanks. However, the high fouling rates experienced in South East Asia means that both the anodes and the metals to be protected rapidly become coated with macrofoulers, which could potentially prevent the anodes from being effective. The present study, involving exposure tests of up to 18 months, indicates that both aluminum and zinc sacrificial anodes remain effective even after being completely coated with biofouling. Furthermore, it was easier to remove the biofouling on the cathodically protected samples than on their unprotected counterparts, possibly due to the higher local pH produced by cathodic protection at the metal and seawater interface.

ChemInform Abstract: Use of a Sacrificial Aluminum Anode in the Acylation of Some Olefins.

ChemInform Abstract: Use of a Sacrificial Aluminum Anode in the Acylation of Some Olefins.

APPLICATION OF ELECTROCOAGULATION PROCESS IN REMOVAL OF ZINC AND COPPER FROM AQUEOUS SOLUTIONS BY ALUMINUM ELECTRODES

In this study, the performance of electro-coagulation in combination with aluminum sacrificial anode, in removal of zinc and copper has been investigated. Several parameters, such as pollutant concentration, pH, electrical potential, COD, turbidity and contact time were studied to achieve a higher removal capacity. Variable concentrations (5-50-500 ppm) of zinc and copper solu- tions were prepared. In order to follow the progress of the treatment, samples of 25mL were taken at 15 min intervals up to 60 min and then filtered with 0.45 ى diameter to eliminate sludge formed during electrolysis. The varying pH of the initial solution was also studied to measure their effects on the zinc and copper removal efficiency. Results obtained with synthetic wastewater revealed that the most effective removal capacities of studied metals could be achieved at 40 V electrical potential. In addition, the increase of electrical potential, in the range of 20-40 V, enhanced the treatment rate without affecting the charge loading required to reduce metal ion concentrations under the admis- sible legal levels. The process was successfully applied to the treatment of an electroplating waste- water where an effective reduction of zinc and copper concentration under legal limits was obtained, just after 15-60 min. Moreover, it can be concluded that the electro-coagulation process has the potential to be utilized for the cost-effective removal of heavy metals from water and wastewater.

Electroreduction of triphenylphosphine dichloride and the efficient one-pot reductive conversion of phosphine oxide to triphenylphosphine

Electroreduction of triphenylphosphine dichloride in acetonitrile was performed successfully in an undivided cell fitted with an aluminium sacrificial anode and a platinum cathode. Further, the one-pot transformation of triphenylphosphine oxide to triphenylphosphine was achieved successfully by the treatment of triphenylphosphine oxide in acetonitrile with oxalyl chloride and subsequent electrochemical reduction.

Finite Element Method Simulation of 35# Steel Cathodic Protection Models in the Seawater

Physical models of cathodic protection (CP) for copper protected by 35# steel and for 35# steel protected by aluminum sacrificial anode respectively in seawater were built in this study. Weak form of Laplace equation was deduced to make finite element method (FEM) numerical calculation conveniently. Then, potential distribution of each physical model was computed by FEM following with measured experiments for validation. Typical FEM simulated data along X-axis and Y-axis of physical models agree well with measured experimental data. For 35# steel protected by aluminum sacrificial anode models, normal cathodic protection, over-protected (OP) and under-protected (UP) models were built, respectively. The results demonstrated that it should be feasible of CP for copper by 35# steel and for 35# steel by aluminum sacrificial anode respectively, and FEM could afford well forecast for CP design in engineering.

Arsenic removal through electrocoagulation: Kinetic and statistical modeling

Arsenic removal from water/wastewater has been the subject of top priority among researchers/industries in recent years due its notorious characteristics. A novel technique of electrocoagulation has been attempted in the present investigation to remove arsenic from aqueous solution. Experiments were carried out in a batch electrochemical reactor using aluminum and mild steel sacrificial anodes. The mechanism of electrocoagulation has been modeled using adsorption isotherm kinetics. Experimental runs were designed by response surface methodology and the influence of combined effects of operating parameters on arsenic removal has been critically examined.

Electrochemical Reactions at Sacrificial Electrodes: Electrochemical Synthesis of Aluminium(III) Alkoxides and their Coordination Compounds

Electrochemical reactions of methanol, ethanol, propan-l-ol, butan-1-ol, pentan-1-ol, hexan-1-ol, heptan-1-ol, octan-1-ol, nonan-1-ol and decan-1-ol (ROH) at sacrificial aluminium anode and inert platinum cathode in the presence of tetrabutylammonium chloride as a conductive additive and acetonitrile as solvent yield aluminium(III) alkoxides. On refluxing with ligand (L) {where L = 2,2’-bipyridyl and 1,10-phenanthroline} these alkoxides don’t form coordination compounds. However, the coordination compounds have been prepared by electrolyzing the solution of above alcohols in the presence of ligand (L) at aluminium anode. These products have been characterized by microanalysis, physical measurements and IR spectral studies.General formula conform to M(OR)3 and M(OR)3.L.{where M- Aluminium and L- ligand}.All these reactions proceed with high current efficiencies.

Influence of Mg and Ti on the microstructure and electrochemical performance of aluminum alloy sacrificial anodes

The experiments focused on the influence of magnesium and titanium as additional alloying elements on the microstructure and electrochemical behavior of Al-Zn-In sacrificial anodes. The electrochemical behavior of the aluminum sacrificial anode with 3 wt.% sodium chloride solution was studied by electrochemical impedance spectroscopy (EIS) tests. It was found that a microstructure with few precipitates and refined grains could be achieved by adding 1 wt.% Mg and 0.05 wt.% Ti to the Al-Zn-In alloy, resulting in the improved current capacity and efficiency of the alloy. The equivalent circuit based on the EIS experimental data revealed less corrosion and lower adsorbed corrosion production on the surface of the aluminum alloy with a combination of 1 wt.% Mg and 0.05 wt.% Ti, which suggested that the corrosion behavior seemed to be strongly related to the presence of precipitate particles in the aluminum alloy, and moderate amounts of precipitate particles could be beneficial to the electrochemical performance of the aluminum alloy sacrificial anode.

Optimization of oil removal from oily wastewater by electrocoagulation using response surface method

Electrocoagulation process with sacrificial aluminium anode was used to separate oil from oily wastewater emulsion. A preliminary experimental study was performed to evaluate the most accurate operating parameters, which are then used for the determination of oil removal efficiency. An experimental design using response surface method (RSM) was then applied and oil separation was estimated by measuring turbidity and chemical oxygen demand (COD). An optimal region characterised with low values of turbidity and COD was found. As part of the optimized process, the main effects of the operational parameters were also investigated. The experimental results indicated that electrocoagulation was very efficient and able to achieve 99% turbidity and 90% chemical oxygen demand (COD) in less than 22 min and current density of 25 mA cm −2. Analysis of variance (ANOVA) showed a high variance coefficient ( R 2) value of 0.998, thus ensuring a satisfactory adjustment of the second-order regression model with the experimental data.

Effect of Mg Content on the Performance of Al-Zn-Mg Sacrificial Anodes

Aluminum sacrificial anodes are widely used in cathodic protection of steel structures in sea water. In the present work, samples of Al-5.3 at.% Zn-x at.% Mg (x = 5.5-8.5) alloys were microstructurally and electrochemically characterized to evaluate their performance as Al-sacrificial anodes for cathodic protection of structures exposed to marine environments. The experiments focussed on the influence of Mg content on electrochemical behavior and efficiency. Mg was used in different concentrations ranging from 5.5 to 8.5 at.%. Short-term electrochemical tests, DNV RP B401, as well as polarization curves and electrochemical impedance spectroscopy were performed to obtain electrochemical behavior and efficiency and to reveal any tendencies to passivation. It is shown that by increasing Mg content an improvement of electrochemical properties of Al-alloy such as current capacity and then electrochemical efficiency can be obtained.

The influence of Ti and Zr on electrochemical properties of aluminum sacrificial anodes

The electrochemical behavior of Al–5% Zn–0.02% In sacrificial anode was studied in 3 wt.% sodium chloride solution. The experiments focused on the influence of Ti and Zr as additional alloying elements on the electrochemical behavior of aluminum sacrificial anodes. For this purpose Ti and Zr were added in different levels from 0.01 to 0.2 wt.%. NACE efficiency and polarization tests were used. It was found that by using 0.03–0.05 wt.% Ti and 0.05 wt.% Zr as the alloying elements; incremental homogeneous dissolution could be achieved resulting in improved electrochemical properties of aluminum sacrificial anodes, such as current capacity and anode efficiency. The results suggest that corrosion behavior seems to be strongly related to the presence of bifilms (doubled-over oxide films) suspended in the liquid alloy. Higher levels of Ti and Zr additions precipitate on the bifilms and cause them to sediment out from the liquid alloy prior to casting, thus depleting the cast alloy of a useful dispersion of corrosion centers, and impairing the uniform distribution of dissolution of the cast alloy.