Sacrificial Zinc Anode Research Articles

Učinkovitost obrade elektrokoagulacije kombinirane s različitim veličinama čestica prirodnog zeolita

In a previous study, the larger size of synthetic zeolite particles was highlighted as better choice for electrocoagulation combined with zeolite (ECZ). This choice resulted in a smaller rise in pH and temperature, a more significant decline in turbidity as well as chemical oxygen demand (COD), and lower electrode wastage, but with greater damage to the electrode surface. The focus of this study was to determine whether natural zeolite of three different particle sizes has the same effect on the ECZ process. The Taguchi method L9 was employed in planning the experiments, with particle sizes of natural zeolite ranging up to 600 μm, three different electrode materials (carbon steel, aluminium alloy, and sacrificial zinc anode), current density in the range of 0.003–0.018 A cm<sup>–2</sup>, and contact time in the range 10–30 min. The Taguchi optimisation results revealed a more significant decrease in COD and turbidity with the smallest particle size of natural zeolite used (90 µm) and with Al electrodes. Evidently, the zeolite particle size, together with the zeolite composition, had a significant influence on the reduction in COD and turbidity. Anode consumption ranged from 0.0172 to 0.6469 g, with minor cathode consumption evident on all electrode materials. Optical microscopy analysis indicated significant corrosion of the anodes, particularly with the largest natural zeolite particle size of 160–600 µm, while minor corrosion damage was also observed on the cathodes.

A comparative numerical evaluation of linear anode arrangements for enhancing above ground storage tank cathodic protection via mesh grid and concentric ring designs

Cathodic protection as a complementary method is one of the most effective ways to prevent corrosion, along with coating and choosing the suitable material. There are different ways to protect the storage tank bottom. Due to the presence of the geo membrane layer and its effective and pivotal role, the use of mixed metal oxide (MMO) anodes is highly recommended. In the current study, the protection process of the above-ground storage tank bottom is simulated using MMO backfilled wire (concentric rings) and ribbon anodes (mesh grid system). In this regard, several parameters must be considered in reaching the protection criteria. The simulation results show that the effect of the limiting oxygen current density, soil resistivity and the anodic current have the greatest role. Anode depth and the spacing between the anodes are also critical factors if they have large values. Due to the importance of the number of conductor bars and feeding cables, two configurations have been presented for ribbon anodes. These configurations have a direct impact on grid resistance, rectifier size, and related costs. Finally, an economic comparison has been made regarding the use of sacrificial and MMO anodes in the form of ribbon next to wire anodes. The results show that, in the use of ribbon anodes, MMO anodes have better performance than magnesium and zinc sacrificial anodes, and the cost required for MMO linear anodes is far lower than the method of sacrificial ribbon anodes. In the present study, the cost of the MMO linear anode system is approximately 20% of zinc and magnesium sacrificial ribbon anode system cost.

Electrocoagulation treatment of compost leachate using aluminium alloy, carbon steel and zinc anode

Analysis of surface changes and corrosion occurrence at the electrode surface, electro-generated sludge analysis, and electrocoagulation (EC) treatment efficiency using aluminium alloy, low carbon steel, and zinc sacrificial anode as electrodes for the treatment of compost leachate with the medium organic load were compared for the first time. Different operating conditions (initial pH values in the range of 4–8, stirring rates in the range 70–270 rpm, and contact times in the range of 10–30 min) were used to study the EC process. Light microscopy analysis show the significant corrosion of anodes, while minor corrosion damage was also observed on the cathodes. Pitting was found on carbon steel and aluminium electrodes, and general corrosion on the zinc electrodes, which increase with the duration of EC (10 to 30 min). Weight loss analysis of electrodes shows a decrease in anode mass in all experiments and aluminium cathode mass, while steel cathode mass increases. Zinc cathode mass increases in initially acid and decreases in an alkaline environment. The highest anode consumption was obtained in the experiment with the Zn electrode (in the range of 0.3300–0.6469 g). SEM/EDS analysis of the electro-generated sludge confirmed the presence of aluminium, zinc, and iron, with oxygen as the main elements, while carbon indicated collected organic matter from the compost leachate. PXRD analysis of sludge shows a mixture of amorphous phase with the a semicrystalline phase of AlO(OH) and the crystalline phase of AlPO4 obtained with Al electrodes, an amorphous structure of the sludge obtained with Fe electrodes, and structurally well-ordered phases of Zn7Cu(OH)13((SiO(OH)3)0.7(O4H7)0.3(SO4)) and (Zn0.9Cu0.1)O obtained with Zn electrodes. In addition, the treatment efficiency was analysed and Taguchi's L9 orthogonal array design was performed.

Effective Use of Sacrificial Zinc Anode as a Suitable Repair Method for Severely Damaged RC Members Due to Chloride Attack

In many cases, the repair strategy by using sacrificial anodes for cathodic protection in real RC structures requires additional zinc anodes after several years due to the decreasing protective area. This experimental study evaluates the effectiveness of time lag application of sacrificial anode cathodic protection applied to RC beam specimens that deteriorated severely due to chloride attack. In the experiment, sacrificial anodes and cathodic protection (SACP) were applied to 41-year-old RC beam specimens exposed to natural marine environments in which the embedded steel bars were significantly corroded. The repair work was performed in three stages. Instant-off and rest potential tests of steel bars were conducted periodically to demonstrate the time-dependent depolarization value. In the first stage, a polymer-modified mortar as a patch repair material was cast to replace the concrete in the middle tensile part with small sacrificial anodes embedded in the mortar. After the protective current reaches an equilibrium state, the sacrificial anodes are disconnected from the steel bars for a year, defined as the second stage. During the one year in the second stage, the steel bar in the patch repair area remained passive, without any sign of corrosion. As for the third stage, additional sacrificial anodes were installed in the existing concrete part to protect the steel in it. From one year of observation after applying sacrificial anodes to old concrete parts, the time lag SACP application of both in patch and non-patch repair parts was clarified to be effective in stopping the corrosion of steel bar in both parts until 20–30 years based on the service life prediction. Doi: 10.28991/CEJ-2022-08-07-015 Full Text: PDF

Monitoring Corrosion in Sacrificial Anodes With Pulsed Eddy Current and Electromechanical Impedance: A Comparative Analysis

Measuring the extent of corrosion of sacrificial anodes used in cathodic protection systems would enable real-time monitoring of the efficacy and remaining useful life of the cathodic protection system. This article presents a comparison of the sensing capabilities of pulsed eddy current (PEC) and electromechanical impedance (EMI) based techniques for measuring extent of corrosion of zinc sacrificial anodes. Experiments were conducted with a lead zirconate titanate (PZT) transducer attached to the sacrificial anode as well as with a PEC probe placed in the vicinity of the sacrificial anode. Accelerated corrosion tests were performed on the anode and the corrosion was quantified by the root mean square deviation (RMSD) of the conductance spectra for the EMI based measurement and area under the curve (AUC) method for the pulsed eddy current based measurement. The experimental results show good agreement with finite element method (FEM) simulations. We report that the EMI method has large sensitivity to onset of corrosion in the anode, with sensitivity reducing nonlinearly over time due to delamination of corrosion by-products. In contrast, the PEC method shows excellent linearity over the entire duration of the accelerated corrosion experiment. A key insight from this work is that an effective monitoring strategy could combine the merits of both sensing mechanisms, with EMI used for identifying incipient corrosion and PEC used for tracking the extent of corrosion over the life of the sacrificial anode.

Термодинамічний аналіз фазового складу протекторних сплавів на основі алюмінію

Literature review on magnesium, zinc and aluminum-based sacrificial anode alloys chemical and phase compositions have been performed. Technological phase diagrams of aluminum-based sacrificial anode alloys with different content of harmful additives, such as iron, silicon and copper, have been calculated and constructed. It is determined that the harmful effect of iron is in faster dissolution of the anode due to large inclusions of iron intermetallic. This iron negative effect can be eliminated in several ways: a) maximization of the melt cooling rate, which will lead to significant grinding of the intermetallics and thus reduce their negative impact; b) high-temperature homogenization of the alloy with subsequent rapid cooling, which will reduce the size of the iron intermetallic inclusions; c) doping the alloy with additional manganese to bind iron in ternary compound, which has a different shape and size than the binary intermetallic and has less negative effect on the sacrificial anode alloy. To eliminate the negative effects of silicon, the alloy has to be additionally doped with magnesium in an amount that will ensure the silicon complete binding. In this case, the phase composition of the alloy will correspond the AP4 alloy (% wt.%: (4.0-6.0) Zn), (0.5-1.0) Mg, (0.05-1.00) Sn , ˂ 0.10 Si, ˂ 0.10 Fe, ˂ 0.01 Cu). Long-term heat treatment of the alloy at a temperature of 120 ° C is proposed to reduce the copper harmful effect on the aluminum-based sacrificial anode alloys. Almost all copper can pass from the solid aluminum solution into the Al2Cu compound during this processing. Keywords: sacrificial anode alloys, aluminum alloys, impurities, technological phase diagrams.

The spontaneous electrochemical reduction of gaseous CO2 using a sacrificial Zn anode and a high-surface-area dendritic Ag-Cu cathode

Carbon dioxide (CO2) has been considered as a green-house gas that causes environmental problems of global warming. On the other hand, the CO2 is a sustainable carbon feedstock, which can be used for the production of value-added products. With rising levels of CO2 in atmosphere, methods capable of converting CO2 into value-added products have become more important. Among several methods, the electrochemical CO2 reduction has attracted much interest because it can alter CO2 to other useful compounds even at relatively low temperatures. In most previous works, the electrochemical reduction of CO2 has occurred only when the cathodic overpotential has been applied in aqueous electrolyte system. In such a system, the continuous electric power has to be supplied and the amount of CO2 delivery has been also limited. In this work, we have designed the gaseous CO2 reduction system using sacrificial zinc anode and dendritic silver-copper cathode. Considering that the standard reduction potential of zinc is further negative than that of CO2, the system has been operated spontaneously, in which the Zn electrode is readily oxidized to Zn(OH)42- ion and gaseous CO2 is reduced. During the spontaneous operation of the system, the power density of 14.97 mW/cm2 has been obtained with the production of carbon monoxide and hydrocarbons such as CH4, C2H4, and C2H2.

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.

Cathodic Protection Range of the Embedded Sacrificial Zinc Anode for RC Member Deteriorated by Carbonation and Mixed Chloride

Much is left unknown about applicable conditions of the method or quantification of the cathodic protection range. In particular, little has been studied about how the range or effect of cathodic protection is influenced by such factors as the thickness of reinforcing bars (rebars) to be protected, combined deterioration by carbonation and mixed chloride, amount of chloride ions and carbonation depth. This study experimentally evaluated the effect of differences in the chloride ion content in concrete, the carbonation depth or the rebar thickness on the cathodic protection range of the embedded sacrificial anode method. The results of the experiment were that the smaller the carbonation depth, the amount of chloride ions or the rebar thickness, the larger the amount of depolarization of the rebars in the concrete to be protected was. That is, for corrosion protection of rebars near patch repair areas embedded with sacrificial anodes, it would be appropriate to make the steel surface area of components smaller and the salt damage environment less corrosive.

Vibration-based inverse graphical technique for thickness estimation of bulk acoustic wave (BAW) resonators: application for corrosion monitoring of sacrificial anodes

Resonant acoustic sensors have been used in a variety of applications that leverage the large sensitivity of mechanical resonance frequency to shift in geometric or mechanical properties of the sensor induced by the measurand. In applications such as structural health monitoring, accurate damage quantification requires development of precise models for resonator-measurand interactions or advanced system identification or optimization algorithms. In this paper, we utilize a graphical technique originally proposed for damage assessment in beams, to determine the extent of corrosion of sacrificial zinc anode discs instrumented with piezoelectric transducers. We develop analytical models for expressing natural resonance frequencies of the radial and transverse vibration modes of a disc in terms of material and geometric properties of its constituent elements. The underlying parameters (in this case, the thicknesses of the zinc and zinc oxide films) are extracted from measured resonance frequencies by finding roots of the characteristic determinant of these modes through graphical technique. Even though accelerated corrosion induced by impressed current results in non-uniform corrosion of the anode, the graphical technique with uniform-corrosion model shows excellent agreement with experimental results and is suitable for in-situ monitoring of sacrificial anodes used in cathodic protection systems. This technique requires no calibration or model of corrosion dynamics, and is computationally inexpensive unlike optimization techniques.

Smart Cathodic Protection System for Real-Time Quantitative Assessment of Corrosion of Sacrificial Anode Based on Electro-Mechanical Impedance (EMI)

Corrosion of metal structures is often prevented using cathodic protection systems, that employ sacrificial anodes that corrode more preferentially relative to the metal to be protected. In-situ monitoring of these sacrificial anodes during early stages of their useful life could offer several insights into deterioration of the material surrounding the infrastructure as well as serve as early warning indicator for preventive maintenance of critical infrastructure. In this article, we present an Electro-Mechanical Impedance (EMI) measurement-based technique to quantify extent of corrosion of a zinc sacrificial anode without manual intervention. The detection apparatus consists of a lead zirconate titanate (PZT) transducer affixed onto a circular zinc disc, with waterproofing epoxy protecting the transducer element when the assembly is submerged in liquid electrolyte (salt solution) for accelerated corrosion by means of impressed current. We develop an analytical model for discerning the extent of corrosion by monitoring shift in resonance frequency for in-plane radial expansion mode of the disc. The model presented here accurately captures the nonlinearity introduced by partial delamination of the corrosion product (zinc oxide) from the disc, and shows excellent agreement with experimental results. Our work establishes the efficacy of the proposed technique for monitoring the state of health of sacrificial anodes in their early stage of deterioration and could thus be widely adopted for structural health monitoring applications within the internet of things.

Experimental Study on Anode Life and Effective Distance of Sacrificial Cathodic Protection in Reinforced Concrete

The purposes of this study were to examine influences of concrete quality and environmental severity on anode life and to determine effective distance of sacrificial cathodic protection in reinforced concrete. 100 x 100 x 400 mm3 concrete beams embedded with a reinforcement at distance of 25 mm from top surface were prepared and sacrificial zinc anode plates were attached on top surface of specimens. 700 x 700 x 75 mm3 concrete slabs embedded with reinforcement mesh of 150 mm spacing were prepared and sacrificial anode were attached on top surface of concrete slabs at lower-left corner. The concrete beams and slabs were then exposed to wet-dry cycle and impressed voltage corrosion accelerations. The anode life was determined by time taken for total consumption of anode in concrete beams and the effective distance was determined by distance influenced by polarization effect of sacrificial anode in concrete slabs. Time taken for total consumption of anode and polarization effect were interpreted from corrosion potential data conducted in accordance with the ASTM C876. As a result, the anode life increased with increasing of concrete quality and decreased with increasing of the environmental severity. The effective distance was approximately 500-600 mm from the anode-installed position.

Influence of Rust Removal Process on The Effectiveness of Sacrificial Anode Cathodic Protection in Repair Concrete

The accumulation of corrosion product on the steel surface may cause eventual failure to deliver of ionic current protection from sacrificial anode cathodic protection. The effect of cleaning of deteriorated steel bar before cathodic protection application is studied in this paper. Two specimens having a length of 580 mm and 150x100 mm of the cross-sectional area with deteriorated reinforcing bar and half-part of chloride contaminated concrete were fabricated to simulate the repair process. Two corroded reinforcing bar with the same surface condition (ø 13mm) were embedded in concrete parallel to each other with the intermediary distance of 40 mm and the cover depth of 30 mm in the bottom surface of the specimen. In the first specimen, rust on the steel bar surface in the repair section was removed. Discrete sacrificial zinc anode is connected to one steel bar in the repair section. During three-years observation, the specimens were exposed to several conditions: 20°C air curing, dry-wet cycle, dry laboratory air, and wet condition, respectively. Potential of both rebar and the sacrificial anode was monitored to understand the performance of the cathodic protection system. The result indicates that rust removal process of steel bar surface in repair concrete part is the most desirable initial condition when the sacrificial anode is applied on it to protect corroded steel bar in new and existing concrete.

Determination of corrosion protection current density requirement of zinc sacrificial anode for corrosion protection of AA5083-H321 in seawater

In this study, the current density requirements of zinc sacrificial anode for corrosion protection of AA5083-H321 aluminum hull for the ship was determined through various electrochemical tests. Surface observation and chemical composition analysis were performed after the galvanostatic test for various current density requirements determined by the cathodic polarization experiment. As a result, the most appropriate current density requirement range was determined as 3.7 × 10−6–5.8 × 10−6 A/cm2. Excessive current density over 7.6 × 10−6 A/cm2 caused local surface damage due to the effect of Mg-rich and Fe-rich intermetallic phases. In addition, the self-consumption of zinc sacrificial anode was determined through Tafel's extrapolation method.

Trace metal biomonitoring in the east Gippsland Lakes estuary using the barnacle Amphibalanus variegatus and mussel Mytilus edulis.

The Gippsland Lakes estuary, a Ramsar listed wetland, in Victoria, Australia, is an area of potential concern for metal pollution due to influxes of human population and associated anthropogenic activities. A biomonitoring exercise was undertaken where the concentrations of 9 metals (Cr, Fe, Cu, Zn, As, Se, Ag, Cd and Hg) were analysed in the soft tissue of two common sessile invertebrates: the mussel Mytilus edulis and the barnacle Amphibalanus variegatus from 6 locations on two different occasions throughout the Gippsland Lakes estuary. A salinity gradient exists in the Lakes, from seawater at Lakes Entrance in the east, decreasing down to < 10 PSU in the west at Lake Wellington during times of rainfall, which is a major factor governing the growth and distribution of both species. Dissolved metal levels in general were low; however, Cu at most sites exceeded the 90% trigger values, while all Zn concentrations exceeded the lowest 80% trigger values of the ANZECC marine water quality guidelines for environmental health. Elevated levels of Cu and Zn were found particularly in barnacles at some sites with environmental contamination due to leaching from anti fouling paints and sacrificial zinc anodes. Elevated levels of Ag and Cd were found in mussels at the Hollands Landing site, which is immediately adjacent to a boat ramp, and Cd and Ag at this site are suspected to originate from inland anthropogenic sources. Concentrations of As in M. edulis across all 6 sites in both sampling periods had mean wet weight As concentrations exceeding the maximum level stated in the FSANZ guidelines. A. variegatus contained elevated levels of Hg especially at the North Arm site with a maximum of 13.6 μg Hg/g dry wt., while A. variegatus also showed temporal changes in Hg concentrations across sites. The maximum Hg concentration found in Mytilus edulis was 1.49μg Hg/g dry wt. at the Hollands Landing site. Previous contaminant studies of biota in the Lakes have targeted sampling of singular predatory or migratory species, such as Black Bream (Acanthopagrus butcheri) and the Burrunan dolphin (Tursiops australis). This is the first biomonitoring study conducted on sessile organisms to assess metal contamination in the system.

Effectiveness of Rusted and Non-Rusted Reinforcing Bar Protected by Sacrificial Anode Cathodic Protection in Repaired Patch Concrete

This study focuses on the monitoring of rusted and non-rusted rebar protected by sacrificial anode cathodic protection until 1000 days. Three specimens of RC beam structures having a length of 580 mm and 150x100 mm cross-section are fabricated. Two reinforcing barwith the same surface condition (ø 13 mm) were embedded in mortar parallel to each other with the intermediary distance of 40 mm and the cover depth of 30 mm in the bottom surface of the specimen. Discrete sacrificial zinc anode is connected to one rebar in patch repair section. During the investigation, the specimenswere exposed under three conditions, i.e., 20°C air curing, dry-wet cycle, and dry laboratory air. Potential of both rebar and sacrificial anode was monitored to check the condition of the cathodic protection system. The result indicates that non-rusted rebar condition in repaired patch concrete (chloride-free) is the most desirable initial condition when the sacrificial anode is applied on it to protect corroded steel bar in existing concrete (chloride contamination).

On the Mitigation of Corrosion Under Insulation (CUI) of Mild Steel Using Local Cathodic Protection

A strategy based on cathodic protection (CP) could be a practically feasible means to protect steel piping from corrosion under insulation. However, experimental studies investigating CP of steel through moist insulation are scarce. Herein, CP was explored to protect insulated steel specimens using sacrificial zinc anodes. The conditions to effectively impart CP through the moist insulation have been discussed. The “throwing power” or protection achieved using sacrificial zinc anodes coupled with mild steel specimens in moist insulation was also estimated using copper electroplating. It was validated that the efficacy of CP depends upon the ionic resistivity of the moist insulation and the moisture content (by volume) must be &amp;gt;25% for efficient ionic conductivity through the insulation. The maximum throwing power of CP through the insulation was achieved when zinc was in direct physical contact with mild steel, with zinc to mild steel area ratio being 1:10.

Performance evaluation of zinc anodes for cathodic protection of mild steel corrosion in HCL

Abstract An assessment of performance of zinc anodes on the cathodic protection of mild steel in 0.5 M hydrochloric acid was made at both the room and elevated temperatures. The cathodic protection reactions process was evaluated by weight-loss method, corrosion rate calculation and potential measurement methods. The effectiveness of zinc sacrificial anodes were found to be cathodically protective on mild steel in the hydrochloric acid at both the room temperature (27 °C) and elevated temperature (60 °C). There was close correlation of the results obtained for the weight-loss method and potential measurement in the HCL environment.

Analysis of an Educational Cathodic Protection System with a Single Drainage Point: Modeling and Experimental Validation in Aqueous Medium.

Cathodic protection, often taught in curricular units, such as corrosion and materials science, is an important subject in the study of chemical engineering. The implementation of lab setups and experimental activities in this field, are core to promoting understanding of the underlying concepts and to developing “hands-on” skills fundamental to the success of future process engineers. This paper reports the influence of different variables on the electrical potential and current behaviors of an educational cathodic protection system operated with a single drainage point. The system comprised a steel bar cathode connected to a zinc sacrificial anode, both placed in aqueous medium. The study variables were the anode area, the cathode diameter, the NaCl electrolyte concentration and the anode placement. Each variable showed a specific influence on the attenuation curves, allowing us to conclude that: (1) increasing the sacrificial anode area, or decreasing the resistivity of the medium, promotes more electronegative potentials on the structure and higher currents; (2) increasing the cathode diameter decreases the protection capacity; (3) positioning the anode in the middle of the cathode lengthwise gives rise to a more balanced potential distribution; and (4), the attenuation curves, both for potential and current, can be successfully predicted using equations based on Morgan and Uhlig’s work. High correlations were obtained between the experimental and modeling data for all the studied variables.

Evaluation of Cathodic Protection Criteria for Embedded Steel Reinforcement in concrete structures

This paper presents the results of performance of sacrificial protection in preventing the rebar corrosion in chloride contaminated and chloride free concrete. In this present study, the effectiveness of sacrificial protection of embedded steel rebars has been evaluated on chloride contaminated and chloride free concrete slabs using ribbon type Zinc anodes with ion conductive polymer backfill over a period of 250 days of exposure. The results showed that the ribbon type zinc sacrificial anodes with the navel electrochemical interface (Ion conductive polymer backfill) can confer effective corrosion protection of embedded steel in concrete on preventing corrosion initiation in chloride contaminated as well as chloride free concretes slabs. The cathodic protection criteria evaluated on concrete unit slab showed that 100-150mV is necessary in the atmospheric exposure and 160-200mV under alternate wetting &amp; drying conditions.