A review on photoelectrochemical cathodic protection semiconductor thin films for metals

Photoelectrochemical(PEC) cathodic protection is considered as an environment friendly method for metals anticorrosion. In this technology, a n-type semiconductor photoanode provides the photogenerated electrons for metal to achieve cathodic protection. Comparing with traditional PEC photoanode for water splitting, it requires the photoanode providing a suitable cathodic potential for the metal, instead of pursuit ultimate photon to electric conversion efficiency, thus it is a more possible PEC technology for engineering application. To date, great efforts have been devoted to developing novel n-type semiconductors and advanced modification method to improve the performance on PEC cathodic protection metals. Herein, recent progresses in this field are summarized. We highlight the fabrication process of PEC cathodic protection thin film, various nanostructure controlling, doping, compositing methods and their operation mechanism. Finally, the current challenges and future potential works on improving the PEC cathodic protection performance are discussed.

Experience on offshore cathodic protection retrofitting in the northern South China Sea

Platforms I and II are steel structures located in offshore areas southeast of the Zhujiang (Pearl) River Delta, the northern South China Sea,. in about 110 in water depth. The jackets, with aluminum sacrificial anodes for cathodic protection (CP) of the immersed zone, were launched in March 1995. In May 096 a CP survey showed that, after almost one year of service, a low polarization level had been achieved and some extended unprotected zones existed; mainly in the deepest part of the Platform II. Further to this, a joint activity was decided in order to assess the need of a possible retrofitting of the CP systems. The results of the activity carried out are dealt with, including technical and economical comparisons amongst several retrofitting options, both with sacrificial anodes and with impressed current systems. The adopted solution is illustrated and data are reported on the level of protection presently achieved.

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

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.%Na Cl 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 ofα(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<0.62 gave the highest corrosion rate and provided the highest cathodic protection efficiency for carbon steel(AISI 1018).Furthermore,the results showed that the anode with Zn/Mg mass ratio<0.62 exhibited a porous corrosion product compared to the other anodes.

EFFECT OF CATHODIC PROTECTION ON FRACTURE BEHAVIOUR OF LOWALLOY STEELS IN SEAWATER

Fracture behaviour of low-alloy steels AIST4340,HY100,Welten60,AISIA537 and A131 in artificial seawater under static,cyclic loading and at cathodic protection potential has been investigated by using the techniques of fracture mechanics, electrochemistry and electronfractography.The results reveal that at hydrogen evolution potentials(cathodic pro- tection potential)the critical yield strength required for the occurrance of SCC decreases from 985 at corrosion potential(E_c)to 872 MPa.The effect of cathodic protection on crack propagation of corrosion fatigue(CF)is not simple,it is closely related to the yield strength of steels and their SCC behaviour.For the steels with high yield strength,cathodic protection promotes(da/dN)_Ⅱ evidently,and reduces △K_(th) value.The(da/dN)-△K curves dis- play a plateau at the third stage of CF for steels with medium or low yield strength.It is men- tioned that the cathodic protection potential for oceaneering constructures should be control- led at top level of the protective range.It seems reasonable that the strength of steel for oceaneeing use might be increased by 200 or 300 MPa.

NUMERICAL MODELLING FOR OFFSHORE PLATFORM CATHODIC PROTECTION-LOCAL SYSTEM

This paper discusses numerical methods for modelling cathodic protation (CP) using Boundary ElementMethods(BEM) for CP design analysis in comparision with the traditional methods and presentsseveral mathematical models (for CP design in 3-D infinite area) solvable by using BEM withmicrocomputer.

Cathodic Protection Remote Monitoring Based on Wireless Sensor Network

Cathodic Protection system is an efficient system used for protecting the underground metal objects from corrosion. In this paper the use of Cathodic Protection (CP) system and how they can be developed to simulate corrosion control solution was illustrated. The aim of developing a Cathodic Protection system is to provide control over oil pipelines and to reduce the incidence of corrosion. The proposed system integrates the technology of wireless sensor Network (WSN) in order to collect potential data and to realize remote data transmission. In this system each WSN receives the data from the environment and forwards it to a Remote Terminal Unit (RTU). Then each RTU forwards it to its base station (BS). In this work Labview 2010 program was used, due to its high potentials. In addition it contains a Tool Kit that supports the wireless sensor network. In this simulation used many cases study to test and monitoring data and get optimum results, least time delay and high speed to prevent corrosion.

Electrochemical characteristics of stainless steel using impressed current cathodic protection in seawater

Stainless steels such as STS 304,316 and 630 are frequently used as shaft materials in small fiber reinforced polymer(FRP) fishing boats.If the shaft material is exposed to a severely corrosive environment such as seawater,it should be protected using appropriate methods.The impressed current cathodic protection was used to inhibit corrosion in shaft materials.In anodic polarization,passivity was remarkably more evident in STS 316 stainless steel than in STS 304 and STS 630.The pitting potentials of STS 304,316,and 630 stainless steels were 0.30,0.323,and 0.260 V,respectively.The concentration polarization due to oxygen reduction and activation polarization due to hydrogen generation were evident in the cathodic polarization trends of all three stainless steeds.STS 316 had the lowest current densities in all potential ranges,and STS 630 had the highest.Tafel analysis showed that STS 316 was the most noble in the three.In addition,the corrosion current density was the lowest for STS 316.

Discussion on Cathodic Protection of HZ 21-1 Platform

The environmental conditions around the first offshore HZ 21- 1 steel wellhead platform in the South China Sea are characterized by deep water, frequent typhoons, rough waves, high water temperature, severely corrosive seawater, and thick fouling organism attachments. The design and effectiveness of galvanic anode protection system are presented, and several methods are described, which are the calculation method of the protective current density considering the variation of water depth, the method of determining protection parameters considering various factors, the arrangement of anodes based on potential distribution and current requirements at different water depths, and the method of anode installation. Finally the effect of the accuracy of selected cathodic protection parameters on the economic benefits of offshore projects is also discussed..

Conductive Mortar as Anode Material for Cathodic Protection of Steel in Concrete

The behavior of a new type of secondary anode material made of carbon fiber reinforced cement used for cathodic protection of steel in concrete was studied. The mechanical, electrical and electrochemical properties of this conductive mortar were investigated. Results indicate that the addition of carbon fiber enhances the strength and ductility of the mortar, as well as the electrical property. The anodic polarization behavior was tested on specimens immersed in aqueous solutions of saturated Ca（OH）2 in the presence or absence of 3% NaCl. Based on impedance measurements the electrochemical parameters of conductive mortar were calculated. It is shown that the investigated conductive mortar can be used in cathodic protection of reinforced concrete. The study also shows that the optimum fiber content in mortar should be in the range from 0.5 vol% to 0.7 vol%.

Research and Application of Platinum/tantalum Composite Anode for Cathodic Protection

This paper introduces the research status and present situation of application of Pt/Ta composite anode materials for cathodic protection in China. It also introduces the corrosion resistance, bending properties and electrochemical performance in seawater and freshwater of the Pt/Ta composite anode materials for cathodic protection. It points out that compared with other platinum composite anodes, the Pt/Ta composite anode has the advantage of small volume, light weight, big drainage rate, long service life, it possesses superiority to be used in the confluence environment of sea water and fresh water and in the medium condition of resistivity changes at all times.

Effect of Cathodic Protection on the Fatigue Crack Growth Behavior of Low Carbon Alloy Steels

The long and short fatigue crack growth (FCG) behavior of 12CrNi3MoV (S1) and 10CrNi5MoV(S2) steel was investigated at cathodic protection in 3.5 % NaCl solution and artificial seawater. The results indicate that long and short FCG show different behavior at cathodic protection. Short FCG is apparently hindered at appropriate cathodic protection potential (-900 mV SCE) and accelerated at over protection potential(-1200 mV SCE). Cathodic protection increases long FCG rate, and the more negative the cathodic protection potential, the greater the long FCG rate. At the same amplitude of stress intensity ( ΔK ), short FCG rate is greater than the long one and their difference becomes less at cathodic protection. The FCG rate in 3.5 % NaCl solution is greater than in artifitial seawater. The FCG rate of S2 steel is bigger then that of S1 steel. The FCG rate of weld bond of S2 steel is lower than that of parent metal and weld beam. In above cases, the anode dissolution, the wedging of corrosion products or deposit and hydrogen embrittlement in long and hort crack tip are also discussed.

Photoelectrochemical cathodic protection of Cu2O/TiO2 p-n heterojunction under visible light

The Cu2O/TiO2 p-n heterojunction composite photoelectrodes were prepared by depositing Cu 2 O nanoparticles on the surface of TiO 2 nanotubes via anodic oxidation and constant current deposition.Field emission scanning electron microscopy(SEM)and high-resolution transmission electron microscopy(HRTEM)analyses showed that Cu 2 O nanoparticles not only deposited on the surface of TiO 2 nanotube array,but also on the wall of TiO 2 nanotubes.The Cu 2 O deposition amount could be adjusted by changing the deposition time.The photoelectrochemical cathodic protection(PECCP)performance of the prepared photoelectrodes for 316L stainless steel(SS)was tested under visible light.The constant current deposition time had a signifi cant eff ect on the PECCP performance of Cu 2 O/TiO 2-X photoelectrodes and Cu 2 O/TiO 2-20 had the best PECCP performance for the coupled 316L SS.This was attributed to the appropriate amount and thickness of Cu 2 O to form p-n heterojunctions with TiO 2,in which separation of the photogenerated carriers was accelerated and transfer of the photogenerated electrons to 316L SS for PECCP was facilitated.

IMPEDANCE CHARACTERISTICS OF CARBON STEEL UNDER CATHODIC PROTECTION

The potential dependence of the faradaic impedance of carbon steels in 3.5% NaCl solution was measured by ac impedance technique. The polarization resistance, and also the cathodic protection efficiency obtained from weight loss, maximized at 0.70 V with respect to saturated Ag/AgCl electrode . Consequently, the potential at faradaic impedance maximum corresponds well to the optimum cathodic protection potential. The study asults showed that the ac impedance technique is a promising method for monitoring and determining the optimum cathodic protection potential.

Triboelectric nanogenerator hybrid array driven by multiform natural energies and its applications in self-powered cathodic protection

In view of the increasing energy shortage and environmental pollution, the collection of friction charges to achieve the conversion of various natural energies and provide in-situ cathodic protection for metals is a significant challenge. Here, we designed a dual device-structure TENG composite array with the triboelectric layer of linear siloxane-modified polyurethane(PU) coating. This array could achieve a comprehensive collection for multiple forms of nature energy and cathodic protection of metals in multi-weather conditions. For one thing, the wave-mode TENG based on tanker structure could collect wave energy and showed the output performance with a short-circuit current of 15.5 μA. For another thing, the droplet-mode TENG based on arc-shaped surface structure could collect raindrop kinetic energy and showed the output performance with a short-circuit current of 16.3 μA. Notably, the parallel array of wave-mode TENG(W-TENG) and droplet-mode TENG(D-TENG) could simultaneously collect wave energy and raindrop kinetic energy, which showed a short-circuit current of 30.7 μA. Besides, a selfpowered a cathodic protection system powered by the dual structure TENG array is assembled and the open-circuit potential drop of the carbon steel connected with the TENG array is about 450 mV. Compared with cathodic protection system powered by single structure TENG, the composite array could provide more effective corrosion resistance for marine equipment in rainy weather. Due to the characteristic for comprehensive collection of nature energy, the anti-corrosion system supplied by TENG parallel array possesses great application potential in the all-weather corrosion protection of metal machinery under complex marine conditions.

The Corrosion Protection Behaviour of Zinc Rich Epoxy Paint in 3% NaCl Solution

Electrochemical impedance spectroscopy (EIS) in the l00 kHz-10 mHz frequency range was employed as the main electrochemical technique to study the corrosion protection behaviour of zinc rich epoxy paint in 3% NaCl solution. The EIS results obtained at the open-circuit corrosion potential have been interpreted using a model involving the impedance of particle to particle contact to account for the increasing resistance between zinc particles with immersion period, in addition to the impedance due to the zinc surface oxide layer and the electrical resistivity of the binder. Galvanic current and dc potential measurements allowed us to conclude that the cathodic protection effect of the paint takes some time to be achieved. The loss of cathodic protection is due to a double effect: the decrease of the Zn/Fe area ratio due to Zn corrosion and the loss of electric contact between Zn to Zn particles. Even when the cathodic protection effect by Zn dust become weak, the substrate steel is still protected against corrosion due to the barrier nature of the ZRP film reinforced by Zn.

Effect of Sacrificial Anode Protection for Steel Pipe Piles at Dandong Port

The sacrificial anode protection system for the steel pipe piles of the 3rd berth of Dandong; wharf at Dandong port has operated for eight years. In this paper, the program design and the protection effect of the sacrificial anode protection system are presented. The results of various inspections show that the piles are protected very satisfactorily.

A Mixed Ether Electrolyte for Lithium Metal Anode Protection in Working Lithium-Sulfur Batteries

Lithium-sulfur(Li-S) battery is considered as a promising energy storage system to realize high energy density.Nevertheless,unstable lithium metal anode emerges as the bottleneck toward practical applications,especially with limited anode excess required in a working full cell.In this contribution,a mixed diisopropyl ether-based(mixed-DIPE) electrolyte was proposed to effectively protect lithium metal anode in Li-S batteries with sulfurized polyacrylonitrile(SPAN) cathodes.The mixed-DIPE electrolyte improves the compatibility to lithium metal and suppresses the dissolution of lithium polysulfides,rendering significantly improved cycling stability.Concretely,Li | Cu half-cells with the mixed-DIPE electrolyte cycled stably for 120 cycles,which is nearly five times longer than that with routine carbonate-based electrolyte.Moreover,the mixedDIPE electrolyte contributed to a doubled life span of 156 cycles at 0.5 C in Li | SPAN full cells with ultrathin 50 μm Li metal anodes compared with the routine electrolyte.This contribution affords an effective electrolyte formula for Li metal anode protection and is expected to propel the practical applications of high-energy-density Li-S batteries.

Study of Discharging Characteristics of Hollow Cathode Surge Protective Gap

A hollow cathode surge protective gap （HCSPG） was designed, and the discharge characteristics was investigated in an air and nitrogen gas environment. For both the gap spacing D and the hole diameter Ф of HCSPG of 3 mm, the voltage protective value Up of HCSPG is about 3.5 kV and its converting time tc exceeds 100 ns at an air pressure from 10 Pa to 100 Pa. The maximum converting time tc from glow to arc discharging reaches 1600 ns at an air pressure of 100 Pa, while the minimum converting time tc is 120 ns at 10 Pa. For a triggered HCSPG, Up is reduced to about 1.6 kV while the converting time is 120 ns with a semiconductor trigger device and 50 ns with a dielectric porcelain trigger device under an air pressure of 100 Pa.

Optimal Piling Network Corrosion Protection System for Al-Zubair Harbor

Cathodic protection is an effective electrochemical technique for preventing corrosion of metallic structures, for large structures like piles network impressed current cathodic protection (ICCP) system is usually preferred. The main aim of this study is to obtain the optimum protection potential that would provide a full cathodic protection for steel piles net-work immersed in sea water at Al-Zubair harbor. The effect of one immeasurable factor (path of anode (χ1)) and two measurable factors (position of anode (χ2) and voltage of power supply (χ3)) on protection potential are studied. Each factor has three different levels (high, medium, and low). Twenty-seven experiments were conducted based on a full factorial design of experiments. The results show that, a sufficient protection for three cathodes can be provided through the electrical circuit connecting them within the appropriate geometric shape.The protection potential is icreased with increasing the voltage of power supply and decreasing of distance between the anode and cathodes (piles network).