Sacrificial Anode For Cathodic Protection Research Articles

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

Development of Al-5%Zn-0.5%Sn-2.6%Mg Alloy as Sacrificial Anode for Cathodic Protection of Steel in 3 wt.% NaCl Solution

In this work, two aluminum alloys, Al-5Zn-0.5Sn and Al-5Zn-0.5Sn-2.6Mg, were prepared by melting in an induction furnace to be used as sacrificial anodes for cathodic protection of marine structures. The alloys are characterized by scanning electron microscopy mapping coupled to energy dispersive X-ray analysis, X-ray photoelectron spectroscopy and X-ray diffraction. Afterwards, the corrosion behavior was studied in 3 wt.% NaCl solution through immersion tests, potentiodynamic polarization, electrochemical impedance spectroscopy and weight-loss measurements. Results display that active dissolution of Al-5%Zn-0.5%Sn-2.6%Mg alloy and its quasi-uniform corrosion is associated with the major precipitates MgZn2 and Mg2Sn particles formed during the melting process. Galvanic coupling measurements over 45 d were carried out on both alloys. The sacrificial cathodic protection of both anodes was successful but the couple efficiency was greater for Al-Zn-Sn-Mg owing to its more negative corrosion potential and uniform dissolution.

Effect of Zn/Mg ratio on cathodic protection of carbon steel using Al−Zn−Mg sacrificial anodes

Abstract Al−Zn−Mg alloys with different Zn/Mg mass ratios were evaluated as sacrificial anodes for cathodic protection of carbon steel in 3.5 wt.% NaCl solution. The anodes were fabricated from pure Al, Zn and Mg metals using casting technique. Optical microscopy, SEM−EDS, XRD and electrochemical techniques were used. The results indicated that with decreasing Zn/Mg mass ratio, the grain size of α(Al) and the particle size of the precipitates decreased while the volume fraction of the precipitates increased. The anode with Zn/Mg mass ratio >4.0 exhibited the lowest corrosion rate, while the anode with Zn/Mg mass ratio

Possibility of High Phosphorus Pig Iron as Sacrificial Anode

Cathodic protection is an effective method to control the corrosion of underground pipelines and submerged structures. In the present work, high phosphorus containing pig iron was utilized as sacrificial anode for cathodic protection of underground mild steel plates and the results were compared with that of a commercially pure magnesium sacrificial anode. Driving potential and current between the galvanically coupled sacrificial anodes and mild steel plates were continuously monitored in real time for one month. Microstructure and morphology of the corrosion products formed on the surface of pig iron, magnesium sacrificial anodes and mild steel plates were observed with the help of optical microscope and scanning electron microscopy, and phase identification were performed using x-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy. The distribution of phosphorus in the pig iron matrix and soluble rust formation on the surface of pig iron under buried condition were critical from the point of sacrificial effect, indicating the possible scientific reasons for high phosphorous pig iron to be used as sacrificial anode.

Galvanic Anodes for Reinforced Concrete Structures: A Review

In recent years, the use of sacrificial anodes for cathodic protection in reinforced concrete structures has increased, reflecting ease of installation, low-maintenance requirements, as well as desirability in prestressed concrete structures where the naturally controlled protection potential decreases the risk of hydrogen embrittlement. Zinc-based alloys have been among the most evaluated galvanic materials for concrete structures, especially in the United States, in many applications: thermal spray, superficial metal/mesh with and without hydrogel adhesive, embedded in concrete (point anodes) with or without salt activator, etc. However, the protection capacity lifetime of zinc alloys as used has been questioned based both on laboratory and on field application studies. Aluminum alloys have also been evaluated, sometimes showing better results as anode materials than zinc alloys. However, both zinc and aluminum alloy anodes may experience limited applicability in concrete structures exposed only to atmospheric conditions, as opposed to those in immersed, tidal, and splash zone service. This paper presents a review of the research work in the literature to date for both laboratory and field evaluations, toward identifying technically relevant situations where the use of sacrificial anodes may or may not be a practical option for reinforcement protection in concrete structures.

Evaluation of the Corrosion of AZ31 Magnesium Alloy Used as Sacrificial Anode for Cathodic Protection of Hot-Water Tank Storage Containing Chloride

Evaluation of the Corrosion of AZ31 Magnesium Alloy Used as Sacrificial Anode for Cathodic Protection of Hot-Water Tank Storage Containing Chloride

Electrochemical Evaluation of Zn-22 wt.% Al- x wt.% Ag (x = 2, 4, 6) Sacrificial Anodes

The object of the present work was to determine the possibility that Zn-Al eutectoid alloys (Zn-22 wt.% Al), with silver contents of 2, 4 and 6 wt.%, could be used as sacrificial anodes for cathodic protection of steel structures in two test aqueous solutions: substitute ocean water and 0.5 M NaCl. Besides the as-cast condition, some samples were homogenized at 350 oC during 96 h and air-cooled. A short-term electrochemical test, DNV RP B401, as well as electrochemical impedance spectroscopy were performed to obtain electrochemical behavior and electrochemical capacity of the anodes, and to reveal any tendencies to passivation. The experimental results suggest that the Zn-Al-Ag sacrificial anodes, with both microstructures, showed a passive behavior in substitute ocean water. However, these alloys exhibited adequate potentials and electrochemical capacities to work as sacrificial anodes in 0.5 M NaCl.

Development of high performance aluminium alloy sacrificial anodes reinforced with metal oxides

Metal composites of alumina and zinc oxide were incorporated into Al + 5% Zn alloy and the reinforced alloys were used as efficient sacrificial anodes for cathodic protection of steel objects. ZnO was not only used to reinforce the alloy matrix and improve the metallurgical characteristics but also to yield effective activation of the sacrificial anodes. Galvanic efficiency as high as 83% was achieved when 0.5% ZnO was incorporated into the anode matrix. High and steady negative potential, very low polarization and substantial reduction in self-corrosion of the anodes were observed during prolonged galvanic exposure tests. However, the incorporation of alumina into the anode matrix led to an adverse effect.

EIS testing of new aluminium sacrificial anodes

Aluminium alloys In/Hg free, suitable as sacrificial anodes for cathodic protection, have been developed. Short-term electrochemical tests were performed on these new alloys to obtain their electrochemical efficiency and to reveal any tendencies to passivation. Samples were galvanostatically held at different current densities, which changed every 24 h according to DNV RP 401. Electrochemical impedance spectroscopy (EIS), polarization curves and electrode potential against time measurements were employed to study the main features of the processes taking place at the alloy–solution interface.

Development of high-driving potential and high-efficiency Mg-based sacrificial anodes for cathodic protection

Development of high-driving potential and high-efficiency Mg-based sacrificial anodes for cathodic protection

Laboratory and Field Characterization of a New Sacrificial Anode for Cathodic Protection of Offshore Structures

A new type of sacrificial anode for cathodic protection (CP) of structures immersed in seawater, such as the steel jackets of offshore platforms, was developed. The anode is constructed of two diverse anodic materials (aluminum alloy on the inside and magnesium in the surface layers) and offers significant reductions in weight and cost of the anodic material. These reductions result from the effect of a highly protective calcareous deposit that forms on the structures. Laboratory scale tests were carried out to simulate and characterize the behavior of anodes in use and to optimize their application. Protective characteristics of the calcareous deposits also were evaluated. Deposits taken from AGIP platforms in the Adriatic sea were analyzed. Traditional aluminum anodes protected the Garibaldi D, which carried two new anodes, and the Daria A was protected entirely with the new type. Such positive experimental results in the field, on platforms in the Adriatic sea, and in laboratory tests enabled this system to be adopted on structures currently under continuous observation.

Aluminium as sacrificial anode for cathodic protection

The performance of commercial aluminium as a sacrificial anode for cathodic protection of mild steel in 0.3% sodium chloride has been studied in alkaline compositions for anolyte based on slaked lime. The influence of several addition agents has been investigated with a view to suppressing local cell action in the above‐mentioned environment.