Anode Cathodic Protection Research Articles

Conducting Composites as Cable Anodes in Cathodic Protection

Conducting Composites as Cable Anodes in Cathodic Protection

Prevention of Chloride-induced Corrosion Damage to Bridges.

The annual direct cost of bridge infrastructure corrosion to the U.S. economy is estimated at $8.3 billion, with indirect costs approximately 10 times higher. Of the approximately 600000 bridges in the U.S., between 15% and 20% are listed as “structurally deficient”, frequently due to corrosion damage. Five technologies are presented for reducing the cost of chloride-induced corrosion damage: (1) conductive coating anodes for cathodic protection of existing reinforce concrete bridges, (2) epoxy-coated rebar (ECR), (3) stainless steel rebar, and (4) high-performance concrete for extending the service life of new structures, and (5) metalizing to provide economical, long-term corrosion protection of steel bridges. Conductive coating anodes and stainless steel rebar represent ongoing work by the Oregon Department of Transportation with final verdicts not expected for years. The ECR and metalizing technology have longer track records and are better established in the bridge construction and protection industry. Application of these technologies is guided by a thorough understanding of their performance, of characteristics of the bridge and its environment, and of the results that are sought.

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.

Synergistic interaction of indium and gallium in the activation of aluminium alloy in aqueous chloride solution

Aluminium alloys are being employed very widely as galvanic anodes for cathodic protection. Aluminium‐zinc‐mercury and aluminium‐zinc‐indium are the popular alloys that are used as anodes. In general, the alloying ingredients activate aluminium and maintain uniform dissolution. In the present investigation, the role of addition of gallium in the ternary alloy of aluminium‐zinc‐indium has been studied by making use of polarisation studies, capacity measurements and galvanic current measurements.

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

Thermal Sprayed Titanium Anode for Cathodic Protection of Reinforced Concrete Bridges

Stable operation of cobalt catalyzed thermal sprayed titanium anodes for cathodic protection (CP) of bridge reinforcing steel was maintained in accelerated tests for a period equivalent to 23 years service at Oregon Department of Transportation (Oregon DOT) bridge CP conditions with no evidence that operation would degrade with further aging. The cobalt catalyst dispersed into the concrete near the anodeconcrete interface with electrochemical aging to produce a more diffuse anode reaction zone. The titanium anode had a porous heterogeneous structure composed of α-titanium containing interstitial oxygen and nitrogen, and a fee phase thought to be Ti(O,N). Splat cooling rates were 10 to 150 K/s, and microstructures were produced by equilibrium processes at the splat solidification front. Nitrogen gas atomization during thermal spraying produced a coating with more uniform composition, less cracking, and lower resistivity than using air atomization.

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.

Microanalysis of Thermal-Sprayed Titanium Anodes for Cathodic Protection of Reinforced Concrete Bridges

Abstract This paper addresses the microanalysis techniques used to characterize thermal sprayed Ti coatings on concrete surfaces as anodes in impressed current cathodic protection (ICCP) systems. Thermal sprayed Ti anodes on concrete were electrochemically aged in laboratory studies of anode performance and service life. A thermal sprayed catalyzed Ti anode was installed on the Depoe Bay Bridge on the Oregon Coast in a field demonstration of the ICCP system. Both air and N were used as the atomizing gases during the study. Thermal sprayed Ti coatings are typically applied in an inert atmosphere or vacuum using shrouds or chambers to prevent reactions with the atmosphere. This was not possible with a structure as large as a bridge. Microanalysis of Ti and N together is difficult and the effects of O add to the complexity of the analysis. The ternary Ti-O-N system has not be well studied.

Electrodes based on Magnéli phase titanium oxides: the properties and applications of Ebonex® materials

Magneli phases are a range of substoichiometric oxides of titanium of the general formula TinO2n−1, (where n is between 4 and 10) produced from high temperature reduction of titania in a hydrogen atmosphere. These blue/black ceramic materials exhibit a conductivity comparable to that of graphite and can be produced in a number of forms, such as tiles, rods, fibres, foams and powders. While these materials have been studied for many years, they have only recently received interest for use as ceramic electrode materials, commercially termed ‘Ebonex®’, and are beginning to challenge precious metal coated anodes for some applications in aggressive electrolytes. Other uses for these materials include electrowinning, electroplating, battery materials, impressed current cathodic protection anodes, electrochemical soil remediation, oxidation of organic wastes, flexible cable materials and electrophoresis. The scope of this review considers the structure and properties of Magneli phase titanium oxide materials, together with their electrochemical behaviour and applications.

Mathematical Models for Cathodic Protection of an Underground Pipeline with Coating Holidays: Part 2 — Case Studies of Parallel Anode Cathodic Protection Systems

Abstract A boundary element mathematical model was used to assess the influence of cathodic protection (CP) design parameters on performance of a parallel-ribbon sacrificial anode CP system for coated pipelines. The model accounted for current and potential distributions associated with discrete holidays on coated pipelines that expose bare steel to the environment. Case studies, based on the CP system used to provide protection to the Trans-Alaska pipeline, were selected to show conditions under which a given CP system will and will not protect a pipe. In the cases studied, Mg ribbons provided adequate protection in 50 kΩ-cm soil, but almost no additional protection was achieved by retrofitting Mg anodes to a CP system using Zn ribbons if the Zn ribbons remained connected to the pipe. The model also was used to show the lack of sensitivity of aboveground on-potential surveys to localized corrosion on the buried pipe.

Bond Strength of Electrochemically Aged Arc-Sprayed Zinc Coatings on Concrete

Abstract Research was conducted to determine the effect of electrochemical aging on large-area arc-sprayed Zn anodes for cathodic protection (CP) of bridges and other reinforced concrete structures. The study focused on the influences of total charge passed and concrete surface preparation on bonding of Zn to the concrete. Half the samples were preheated prior to being arc-sprayed with Zn. The preheated samples had initial bond strengths 80% higher than the unheated samples. This difference became insignificant after ≈ 200 kcoul/m2 (5.2 A-h/ft2). Bond strengths for all samples started to decrease after ≈ 600 kcoul/m2 (15.5 A-h/ft2). Changes in bond strength were correlated with observed changes in permeability of the Zn coating to water, electrical behavior of the Zn-concrete interface, charge-transfer resistance, and chemical composition at the Zn- concrete interface.

Development of Conductive Polyester Concrete for Bridge-Deck Cathodic Protection and Ice Control

An electrically conductive polymer concrete was developed and field tested by the California Department of Transportation. The conductive polymer concrete was a blend of polyester resin, mineral aggregate, and carbon in the form of coke breeze. After laboratory work it was used as an anode for cathodic protection (CP) of reinforcing steel on two bridge decks and used as a heater on another. The first CP system was placed on an entire bridge deck in 1988. Field data generated from 1988 to 1996 indicated it was quite successful, although there were some shortcomings. Following improvements a second bridge deck CP system is being placed. Use of the polymer as a heater was tried in 1990 by placing a 3 m2 (10 ft2) test section on a deck located on I-80 in the Sierra Nevada mountains. The heater was evaluated during the winter of 1990–1991. The results of the evaluation indicated such a heater is feasible.

Characterization of Activated Titanium Solid Reference Electrodes for Corrosion Testing of Steel in Concrete

Abstract Small bars of Ti activated with mixed-metal oxide (commercially produced for permanent impressed-current anodes in cathodic protection) were used as embedded reference electrodes (RE) in c...

Optimal Positioning of Anodes for Cathodic Protection

We consider an optimal control problem that arises in cathodic protection. The control is the position of a finite number of anodes, each with a prescribed current density. The goal is to obtain a desired potential distribution on the cathode that will prevent or reduce cathodic corrosion. The existence of an optimal solution is proven. The differentiability of the functional minimized is justified, and the equations satisfied by the derivative are established. Then a numerical algorithm is proposed for computing the optimal position of the anodes. Finally, we present some numerical results obtained by implementing the proposed numerical algorithm with a boundary element method.

Aluminium Alloy Anodes for Cathodic Protection of Marine Structures

Aluminium Alloy Anodes for Cathodic Protection of Marine Structures

Impressed current cathodic protection and its effect on marine paint systems

The operation of impressed current cathodic protection devices on ships frequently results in some destruction of the paint coating on the rest of the structure. The reasons why these devices are more aggressive to paints than laboratory work suggests are explored and the operational parameters of practical systems described. The use of a conductive paint to simulate an anode is introduced as well as tests which have shown that a conducting paint film may be used as a cathodic protection anode with significant improvement in corrosion protection in high resistivity environments.

Cathodic Protection of Offshore Structures

Synopsis A brief introduction is given to the theory of cathodic protection. Principles and design procedures are described for both sacrificial anode and impressed current cathodic protection with a comparative assessment of both systems and the anodes used in them.

Titanium in the Oil Industry

Introduction Titanium is becoming increasingly widely used in the oil industry in such areas as exploration/production, pipelines, underwater operations, engineering/construction and refining. The applications mainly depend on the unique corrosion resistance of the material in seawater but some use is made of the high specific strength of titanium alloys and also of their excellent resistance to cavitation and erosion. Potential and established uses of titanium include tube‐in‐shell and plate type heat exchangers, equipment for data logging, tanker purge systems, pumps and valves, fixtures and fittings, cathodic protection anodes and submersibles for underwater operations.

FRP船のCu-Al合金製プロペラの腐食と防食について

In the first report it was shown that damage of metallic propulsive device (Cu-Al alloy propeller) on FRP ships was caused by electrochemical corrosion and could be prevented by supplying sufficient, cathodic protective current. The purpose of this research are to find the stray current that might cause corrosion of the propeller and to determine the protective current density to Cu-Al alloy. Measurements were carried out on the stray current to Cu-Al alloy and on the dissolution rate of zinc anodes for cathodic protection of propellers while running and while stopping. The following conclusions were obtained: (1) The stray current was not directly related to the corrosion of the propeller. (2) The dissolution rate of zinc anodes for cathodic protection of propeller was closely related to the corrosion of the propeller. (3) The protective current density required for protection of Cu-Al alloy was 425mA/m2.

人工海水中におけるアルミニウム合金の流電陽極試験

The tests of galvanic anodes for cathodic protection were conducted on materials of Al-Zn, Al-Sn, Al-Cd, and Al-Zn-Sn alloys in an artificial seawater by using an apparatus for galvanostatic electrolysis. Corrosion aspects of the test pieces after 10-day immersion were analyzed by X-ray diffraction patterns and discussed by Hansen's Constitutional Diagram of Binary Alloys. The following conclusions were deduced from the change in anodic potential of aluminum alloys during 10 days and the current efficiency after that period: (1) Among Al-Zn alloys, Al-Zn (5.0-10.0) alloys showed good results. (2) None of Al-Sn and Al-Cd alloys were promising. (3) Among Al-Zn-Sn alloys, Al-Zn(3.0)-Sn (0.5) alloy and Al-Zn(3.0)-Sn (1.0) alloy had the best results.