Cathodic Protection Of Steel Research Articles

Cathodic Protection of Steel in Concrete Using Conductive Polymer Overlays

Cathodic Protection of Steel in Concrete Using Conductive Polymer Overlays

水道水中における鋼の犠牲アノード方式によるカソード防食

水道水中における鋼の犠牲アノード方式によるカソード防食

CASE STUDIES OF USE OF DESIGN OF EXPERIMENTS IN MATERIAL RESEARCH

The paper describes principles of factorial and fractional factorial design of experiments. The various ways of analysing data obtained by these procedures are shown via four case studies. Yates method was followed in case 1 where the effect of anode type, carbon content of steel, temperature, and agitation on cathodic protection of steel in seawater, on current density, was studied. In case 2, a glass was formulated within 10 constituante melted, quantity water and tested for flow caracteristics, from the result the factor effect was calculated. In case 3, analysis of results is done in a very simple way. In this case, the effect of carbon content, surface condition, temperature, and agitation on the corrosion of steel in seawater was studied. In case 4, the effect of eleven constituents on acid resistance of a cast iron enamel has been studied through sixteen experimental compositions. This case gives a method to find out which of the sixteen experimental compositions is nearest to a target value.

Model Investigation of the Peculiarities of the Corrosion and Cathodic Protection of Steel in the Insulation Defects on Underground Steel Pipelines

The new data of model investigations on cathodic passivation, nature of galvanic macrocells, and the dimensional effects in the defects of insulation on underground pipelines are analyzed. Partially revising some conventional concepts concerning the mechanism of the corrosion and cathodic protection of steel in soils is advisable.

Anwendung des kathodischen Korrosionsschutzes für den Bewehrungsstahl in Beton / Applications of Cathodic Protection to Steel in Concrete

Abstract The paper deals with the application of cathodic protection of steel in atmospherically exposed reinforced concrete. The use of this technique to control corrosion rate in chloride contaminated constructions and to improve the corrosion resistance of reinforcement in new structures expected to become contaminated is discussed. The more recent applications of cathodic protection on carbonated concrete are also considered. For each type of application, principles and operating conditions (potential and current applied, throwing power, risk of hydrogen embrittlement in the case of prestressed structures) are discussed. Examples of cathodic protection and prevention in bridges, and buildings are reported.

Non‐destructive determination of the sheet resistance of conductive coating anodes on concrete

Conductive coatings form the basis of a common anode system used in the cathodic protection of steel in concrete. One of the properties required by such a coating is a low sheet resistance (square resistance). This, together with the protection current density and anode connection geometry, determines the uniformity of the current distribution over the concrete surface. It is shown that the sheet resistance may be determined using a non‐destructive test employing a collinear four‐probe array. When a current (I), passed between the outer probes of an equally spaced four‐probe array, induces a voltage difference (δV) between the inner probes, the sheet resistance is given by (pgr;/ln2)x(dgr;V/I). The validity of the measured values may be assessed by the absence of any sensitivity to probe orientation and spacing. This technique may be used in the assessment of the quality of installed conductive coating anodes. The sheet resistance will depend on factors such as the thickness and age of the installed coating.

Rotating Ring-Disk Studies on the Impact of Superimposed Large Signal ac Currents on the Cathodic Protection of Steel

Corrosion experiments with dc and ac polarisation were carried out in neutral aerated solutions using a rotating ring-disk electrode (RRDE) with a mild steel (ST 1.0037) disk and a platinum ring electrode. Combined with solution analysis and weight loss measurements, the influence of superimposed large signal ac currents on the anodic iron dissolution was studied by analysing the ac current signal at the ring electrode i R as a function of the frequency (f: 0, 5 ,16 2/3, 30, 50 Hz), the effective ac current density of the disk (i D,eff : 1, 5, 10, 15, 20 mA cm -2 ) and different cathodic dc protection current densities (i = D : -0.1, -0.5, -1.0 mA cm -2 ). Measurements were performed in sodium sulphate solutions (pH 5) and in systems where a defined carbonate layer is formed on the iron disk electrode (0.3 M NaCI, CaCO 3 + CO 2 , pH 5.8). The time average ring current density, which is proportional to the dissolution rate of the iron disk, was found to increase with increasing ac current density but decreased with increasing frequency f and cathodic dc protection current density i = D . After iR-drop correction of the maximum disk potential a unique current density potential curve of iron dissolution can be obtained, which fits all data obtained independent of the frequency and ac amplitude applied. This polarisation curve provides to determine a threshold potential for cathodic protection under ac polarisation conditions.

Current densities for cathodic protection of steel in tropical sea water

AbstractMass losses have been measured for sacrificial anodes used for the cathodic protection of steel structures in tropical sea water off the coast of Singapore. By converting these mass losses to average current density values over the exposure time, information has been provided which may be used to predict the mass of sacrificial anodes needed to ensure adequate cathodic protection during the design life of steel structures in this environment. The average current density for cathodic protection of steel during the first day of exposure in Singapore sea water was found to lie in the range 711–2134 mA m−2, depending on the sea water current, anode type (zinc or aluminium), steel type (carbon content), and depth of exposure (2 or 12 m). The average current density fell with increasing time of exposure to 114·0, 58·0, and 19·1 mA m−2 for 2 months, 9 months, and 13 years exposure respectively. Equations expressing the average current density as a function of time for different depths in Singapore sea wa...

Current densities for cathodic protection of steel in tropical sea water

Current densities for cathodic protection of steel in tropical sea water

Cathodic Protection of Steel by Electrodeposited Zinc-Nickel Alloy Coatings

Abstract The ability of electrodeposited zinc-nickel alloy coatings to cathodically protect steel was studied in dilute chloride solutions. The potential distribution along steel strips partly electroplated with zinc-nickel alloys was determined, and the length of exposed steel that was held below the minimum protection potential (Eprot) was taken as a measure of the level of cathodic protection (CP) provided by the alloy coatings. The level of CP afforded by zinc alloy coatings was found to decrease with increasing nickel content. When nickel content was increased to ≈ ≥ 21 wt%, no CP was obtained. Surface analysis of uncoupled zinc-nickel alloys that were immersed in sodium chloride (NaCl) solutions showed the concentration of zinc decreased in the surface layers while the concentration of nickel increased, indicating that the alloys were susceptible to dezincification. The analysis of zinc-nickel alloy coatings on partly electroplated steel strips that were immersed in chloride solution showed a signif...

Cathodic protection of steel in concrete

Cathodic protection of reinforced concrete has been developed by a combination of trial and error, fundamental research, applied research and transfer of technology from related fields. These developments have been underway for 35 years and have been progressed by civil engineers, concrete technologists, corrosion scientists and cathodic protection engineers. In the past 6 years in the U.K. the investment in repairs to reinforced concrete structures incorporating cathodic protection has grown from a minimal £100,000 p.a. to some £20 million p.a. This paper reviews the developments in cathodic protection of reinforced concrete during the last 35 years with particular emphasis on developments during the last decade. The critical areas of this multi-discipline technology in respect of system performance and future development are anode systems, anode overlays and assessment of cathodic protection performance. These critical areas are addressed in detail and some requirements for future work are highlighted.

Hydrogen absorption resulting from the simulated pitting corrosion of carbon-manganese steels

Hydrogen permeation measurements were performed on membranes of BS4360 Grade 50D C-Mn steel in the quenched and tempered condition. The rates of hydrogen absorption resulting from exposure to FeCl 2 solutions in a simulated corrosion pit were measured and found to be lower than those occurring in artificial sea water at applied potentials in the range commonly used for cathodic protection. A progressive decrease in the hydrogen permeation flux was recorded during simulated pitting and was attributed to the formation of a partially protective film of magnetite on the steel surface. At cathodic applied potentials iron plating was observed on the membranes. It is suggested that a similar process occurs in the cathodic protection of steel containing real corrosion pits and leads to a lowering of the Fe 2+ ion concentration within the pits and a decrease in the aggressiveness of the local environment.

Cathodic Protection of Steel Embedded in Porous Concrete

AbstractThe feasibility of applying cathodic protection to carbon steel strands embedded inporous concrete exposed to a chloride-containing environment was investigated. In-situ polarisation experiments were conducted on the embedded steel using a current-interrupt technique. This enabled the magnitude of the iR drop to be determined, and the actual (or corrected) potential of the embedded steel to be monitored throughout the experiments. The results suggested that, for the porous concretes which were examined, the minimum cathodic potential required to protect the embedded steel depended on the concentration of chlorides in the environment. These potentials are −260 mV SHE (−578 mV CSE) for a 0·02 M NaCl environment and −410 mV SHE (−728 mV CSE)for 0·7 M NaCl or sea water solutions.

Cathodic protection of steel in offshore concrete platforms : O. E. Gjorv and O. Vennesland. Mat. Perform. May 1980, 19(5), 49–52

To improve existing corrosion-control criteria for offshore concrete platforms, researchers studied the effects of various polarization levels on the reinforcement-bar bonding. Experimental investigations indicate that polarization of embedded steel down to -1350 mV (vs a saturated calomel electrode) has no harmful effect on bond strength and may even improve the bond strength of initially clean and smooth steel. For increasing polarization levels, fewer chloride ions from the seawater penetrate the concrete; a calcareous coating on the concrete surface may form at high polarization levels. The current necessary for cathodic protection of embedded steel is controlled primarily by the rate of oxygen diffusion through the concrete. Measurements indicate that the resistance to oxygen diffusion may be 10 times higher through the interface between the concrete and steel than through the concrete cover. The current density necessary for polarizing embedded steel in offshore concrete platforms may be as low as 0.014 mA/ft/sup 2/ (0.15 mA/m/sup 2/).

Corrosion of the inside surface of penstocks

1. The corrosion rate of steel in flowing water of the Mingechaur reservoir is within 0.47–1.08 mm/yr, decreasing rapidly with exposure [3, 4]. 2. Considerable initial values of the cathodic current density, equal to 1–1.5 mA/dm2, are needed for cathodic protection of steel in the same flowing water; however, they decrease rapidly both as a result of the formation of cathode deposits and as a result of the formation of natural films and deposits on the metal. 3. Anodic dissolution of metal in a freshwater flow occurs at the same rates as in nonflowing water.

Cathodic protection of steel in concrete

Cathodic protection of steel in concrete

陰極防食用鉛合金陽極の研究 (第7報) 硫酸溶液中の鉛および鉛合金の陽極腐食について

In order to investigate on cathodic protection of steel and stainless steel used for holding sulfuric acid, examination was conducted to check the behavior of pure lead, lead alloys and high-silicon iron in sulfuric acid solution. The experiments were done by measuring the anode potential and analysis of surface film by oxalatimetry.The results obtained are as follows:1) The growth rate of passive film on Pb, Pb-As, etc. follows parabolic law.2) Those on Pb-Te, Pb-Ag, etc. follow the logarithmic law.3) The amount of lead peroxide on Pb-Sn and Pb-Cd electrodes decrease in proportion to the lapse of time.4) Allowable current density for Pb-Ag anode is considered to be approx. 10A/dm2.5) High-silicon iron may be used at the current density of 4A/dm2, while its weight loss caused by corrosion reaches 0.05g/A·hr and is far larger than those of lead alloys examined.

Current and Potential Relations For the Cathodic Protection of Steel In a High Resistivity Environment

Abstract In order to evaluate potential and current criteria for the cathodic protection of bare low-carbon steel in a high-resistivity environment, specimens were exposed in the laboratory for a period of two months to a soil having a resistivity of about 20,000 ohm-centimeter. Previous work in low-resistivity environments has shown that corrosion can be reduced to a negligible degree by polarizing a steel structure to —0.85 volt (protective potential) with reference to a copper-copper sulfate electrode. In such studies, cathodic polarization curves have also been shown to be useful in indicating the current density required for cathodic protection. In the present study the above criteria were again evaluated. In addition to protecting the steel at the protective potential (free of IR drop), the effect on protection of including IR drop caused by the protective current was also noted. Also, cathodic polarization curves were obtained on a recorder in conjunction with a bridge circuit to eliminate the IR drop. The results show that the best degree of protection was achieved on the specimen controlled at —0.77 volt (without IR) with reference to a saturated calomel half-cell. This is approximately equivalent to the protective potential —0.85 volt with reference to the copper-copper sulfate electrode. Applied current indicated by the break (change-in-slope) in the cathodic polarization curve agreed reasonably well with the actual current necessary to maintain polarization at —0.77 volt (free of IR). The current required for protection was about three times the magnitude of the corrosion current; therefore, the corrosion reaction was either under anodic control (unlike previous studies) or an equivalent type of control which was caused by high resistance at anodic areas. 5.2.4

Principles and Criteria for Cathodic Protection Of Steel in Sea Water—A Review★

Abstract Development of cathodic protection is traced from the initial work of Davy to the formation of an adequate theory of cathodic protection. Techniques used in experimental determination of criteria for protection in laboratory and in field are given with the advantages and limitations of each. Reference list includes 84 items. 5.2.4

Current and Potential Relations for The Cathodic Protection of Steel in Salt Water★

Abstract A laboratory investigation was made pertaining to the cathodic protection of steel specimens that were exposed for 60 days to both stagnant and aerated city water, to which was added 3 percent by weight of sodium chloride. Major consideration was given to the significance of potential as a criterion for protection. Optimum protection was achieved when specimens were controlled at —0.77 volt with reference to the saturated calomel half cell. Although a good degree of protection was obtained at controlled potentials more noble than —0.77 volt, that is, at the potentials associated with the breaks in cathodic polarization curves, this lesser degree of protection could not be obtained at lower mean current densities. 5.2.4