Papers by Keyword: Cathodic Protection (CP)

Abstract: The hot-dip coatings containing Zn-Al-Mg-Ce were prepared through congruent melting. The anti-corrosion performance of the coatings was researched using the weight loss rate by the neutral salt spray testing. The reasons of the effects of the elements Al, Mg, Ce on the anti-corrosion performance promoting were researched through the analysis of Scanning Electron Microscope and the polarization curves. The results showed that Al, Mg, Ce embedded in the Zn matrix uniformly and the protective effect for the steel was enhanced by the electrochemical action.

Abstract: For the jack-up platforms' huge size and complex structure, as well as the variation and complexity of their ambient corrosion environment, problems often arise in cathodic protection (CP) systems. The rise of the computer and the numerical simulation technology provide a new technical method to the prediction, evaluation and optimization of CP system for jack-up platform. Numerical simulation method has the advantage of examining potential maps of the entire structure easily and then the designer can determine the number and placement of anodes required to provide protection from the under and over protection regions based on a generic polarization response. In this paper the 3-D boundary element method was used to calculate the mathematical model of sacrificial anode CP system for a jack-up platform. Introduced piecewise quasi linearized method to deal with nonlinear problem of boundary conditions. Adopt block boundary element method to solve electrolyte inconsistency problem and points regional modeling to solve electrolyte discontinuous. From the results we can conclude that the jack-up platform sacrificial anode CP system meets the protection targets.

Abstract: In the present study, corrosion and cathodic protection (CP) characteristics of concrete piles exposed to marine environments such as marine bridge columns or pier structures were evaluated under simulated conditions. The accelerated environmental tests were carried out at an elevated temperature (40°C) and a high chloride concentration (15%). The protection potential of CP systems with Zn-mesh sacrificial anodes applied to piles was inversely proportional to the water content in the concrete. When the CP system was applied after corrosion initiation and propagation (CProt), the protection current density was higher than when the CP system was applied at the beginning of structural construction (CPrev). However, the four-hour depolarization potential was higher in the latter case than in the former. In addition, it was found that even though the current density of the CPrev system was relatively lower than that of the CProt system, the CPrev system was also able to prevent corrosion. Consequently, both CProt and CPrev systems are very effective at preserving reinforced concrete structures, especially in marine environments.

Abstract: With rising demands, oil and gas exploration of high-pressure high-temperature (HPHT) wells are increasing worldwide. Due to aggressiveness of HPHT environments, piping and equipments are constructed with high-strength corrosion resistant alloys (CRAs). Duplex stainless steel is one of the candidate alloys that offer high strength along with corrosion resistance. It possesses the advantages of both austenitic and ferritic stainless steels and hence, the name duplex or dual phase stainless steel. In order to control corrosion, cathodic protection is commonly being employed on the structures and equipment. Cathodic protection is accomplished by applying a direct current to the structure which causes the structure potential to change from the natural corrosion potential (E_corr). The required cathodic protection current is supplied by sacrificial anode materials or by an impressed current system. Hydrogen embrittlement (HE) is an associated phenomenon, which results in the production of hydrogen ions, leading to its absorption in the protected metal and subsequent hydrogen embrittlement of metals and welds. To prevent this embrittlement, cathodic protection is closely studied in terms of finding the critical potential, pH, temperature etc. that does not cause hydrogen embrittlement. This paper describes the study carried out to find the role of pH on the absorption of hydrogen in Duplex Stainless steel. It has been observed that at a critical pH, hydrogen intake in the sample is very high, as compared to the pH below and above the critical pH. Critical pH observed for duplex stainless steel is a trade of between hydrogen evolution and absorption for given duplex structure.

Abstract: This study is to acquire the confirmation data regarding the cathodic protection (CP) characteristics for slabs in marine bridges and piers exposed to hash seawater environments. It was possible to confirm the performance of CP only by the measurement of CP potentials for the slab specimens applied with zinc mesh sacrificial anode CP system. The CP current density for the cathodic protection (CProt) that CP started after a repair of corrosion was 2 times higher than that for the cathodic prevention (CPrev) that CP commenced from the beginning of experiment, and the most of protection current density (87.0-91.5%) flew to the closer top rebar in slab specimens. 4 hour depolarization potentials were higher in the CPrev system than in the CProt one, and it was confirmed that the CPrev has more protection effect with less protection current, comparing to the CProt. It was also confirmed that the CP of both CPrev and CProt by means of zinc mesh sacrificial anode for reinforced concrete structures were very effective corrosion protection technology in marine environment.

Abstract: The electrochemical performance of Mg-Al alloy composite sacrificial anodes in seawater was studied. The results show that Mg-Al composite anode can keep the electrochemical characters of Mg anode and Al anode respectively. The protection process of Mg-Al composite anode includes 4 steps: (1) Mg anode protects the steel, (2) interface oxides expose in seawater and anode performance decreases, (3) interface oxides dissolve in seawater and Al anode begins to work, (4) Al anode protects the steel efficiently.

Abstract: This experiment represents the effect of impressed current cathodic protection with a variable resistor on concrete specimens. The effect of cathodic protection (CP) system on concrete structures can be changed at different condition. Especially, in marine concrete structures, it is difficult in applying impressed current CP by means of one rectifier in both high resistivity area (dry area) and low resistivity one (wet area). Thus, in this study, the variable resistor was utilized to fulfill similar CP effect on both high resistivity zone and low resistivity one in order to manage the problem. Specimens were concrete slab type with a base of 400mm × 400mm and a height of 70mm. Test factors were CP potential, CP current, and 4-hour depolarization potential. Test results showed that the variable resistor could have positive influences on an improvement in CP effects. In addition, environmental conditions had to be considered to reach enough CP potential and current in this system.

Abstract: The aim of this study was to obtain special cathodic protection (CP) behavior in coastal bridge structures. This bridge structure was located to the area where repetition between fresh water and sea water taken place due to ebb and flood tide. In this study, zinc-mesh anode was used as a sacrificial anode. Thus, it was a good opportunity to verify the effectiveness of sacrificial anode CP (SACP) in this special location. Measurement was conducted for three years. Test Factors were corrosion potential, CP potential, 4 hour depolarization potential, and CP current. Moreover, resistivity and corrosion rate were measured by the multi-functional corrosion monitoring sensor (DMS-100, Conclinic Co. Ltd) that could measure potential, galvanic current, corrosion rate, concrete resistivity, and temperature. After three years from installation of CP, it could confirm that although some pier showed low depolarization potential less than 100mV, most piers showed good protection both electrochemical and physical aspects.

Abstract: This paper create a numerical model of potential distribution on the carbon steel pipe in seawater,and use the COMSOL to numerically calculate the potential distribution, and then studies the factors, anode location, quantity, size and medium conductivity etc, which influent potential distribution of cathodic protection.Meanwhile,the paper take a method which through the orthogonal array parameters scanning to determine the best protection scheme about anode location, number,and size,which provide the academic support for engineering practice.

Abstract: This study represents the result of hybrid cathodic protection (Hybrid CP) system application. Hybrid CP, which is the combination between sacrificial anode cathodic protection (SACP) system and impressed current cathodic protection (ICCP) system, can be optimum way to protect corrosion, especially in concrete columns. In this study, sections below a water line, i.e. submerged and tidal zones, were cathodically protected by means of SACP. In addition, ICCP was applied to the upper areas of water line, i.e. splash and atmospheric zones. Water level was changed to verify the effectiveness of hybrid CP system. The test factors were natural, CP, and 4-hour depolarization potential.