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1.
The influence of dissolved oxygen on calcareous deposits formed under galvanostatic polarization mode was studied.When the dissolved oxygen concentration was less than 7 mg L~(-1),the cathodic protection potential showed a plateau at the initial polarization,and then quickly shifted negatively.While the dissolved oxygen was more than 9 mg L~(-1),the potential shifted negatively in a linear form.After 168 h of polarization,the final protection potential shifted negatively with the decreasing dissolved oxygen concentration.The deposition progress was monitored by electrochemical impedance spectroscopy,and only one single loop was found in Nyquist diagram,indicating deposits of ineffective protectiveness precipitation under the experimental conditions.The protection factor of deposits increased with the decreasing dissolved oxygen concentration which was detected by linear polarization resistance technique.The cathodic electrochemical reaction could change very shortly from oxygen reduction to hydrogen evolution after cathodic protection under very low dissolved oxygen concentration,such as 1 mg L~(-1),resulting in the hydrogen bubbling from the metallic surface and the decrease of deposits protection factor.Observation by scanning electron microscopy and X-ray diffraction analysis demonstrated that the deposits were mainly of calcite under the experimental conditions,and that dissolved oxygen had no effect on the crystalline types of calcium carbonate. 相似文献
2.
《中国海洋湖沼学报》2021,(5)
A new research proposal was introduced aiming at solving the fundamental theory for reducing the risk of hydrogen embrittlement(HE) in high-strength steels by utilizing hydrogen-consuming microorganisms.The superior performance of high-strength steel can meet the material strength requirements for remote deep-sea marine engineering development.Due to the heavy corrosive marine environment,steel structures must be protected by cathodic protection.However,high-strength steel is sensitive to stress corrosion cracking and HE,and cathodic protection can promote hydrogen permeation into steel.Hydrogen-consuming microorganisms are widespread in the natural environment and they utilize the energy of hydrogen oxidation to survive.If we could make use of the hydrogen-consuming function of microorganisms to consume the hydrogen generated during the cathodic protection process,then the potential for cathodic protection can be reasonably lowered,ideally protecting the steel and simultaneously reducing the possibility of HE. 相似文献
3.
IMPEDANCE CHARACTERISTICS OF CALCAREOUS DEPOSIT 总被引：1，自引：0，他引：1
The electrochemical impedance spectra for bare steel and sample covered with calcareous deposit in artificalseawater were determined; the dependence of the impedance on the potential was investigated, thesignificance of the impedance parameter R_f reflecting the effective protectiveness of the deposit is emphasized.Optimization of the cathodic polarization condition is discussed. 相似文献
4.
《中国海洋大学学报(英文版)》2015,(2)
The current distributions over carbon steel under iron red alkyd primer exposed to 3.5% sodium chloride solution were mapped using the wire beam electrode(WBE). The electrochemical impedance spectroscopy(EIS) of the WBE was carried out to analyze the performance of coating delamination and corrosion behavior of carbon steel beneath defective coating. The EIS data revealed that protective capability of coating decreased with immersion time and the degree of cathodic delamination showed a rapid rise. The current density distribution of WBE indicated that cathodic sites was located at the defect at the beginning of immersion and gradually spread into the intact coating. The cathodic regions were distinguished from the anodic area and distributed over the WBE. The changes of cathodic sites could reflect the deterioration process of defective coating. The cathodic area ratio was a more useful parameter than the cathodic delamination degree to evaluate the coating cathodic delamination. The polarity reversals of electrodes at the defect and beneath coating were observed. A simple discussion of relationship between the blister and the polarity reversal was made from a standpoint of electrochemical distribution. WBE method was able to map and record the changes of local cathodic sites beneath defective coating in real time, which could provide more detailed information about the local degradation of coating. 相似文献
5.
CHARACTERISTICS OF THE OXYGEN REDUCTIONIN ATMOSPHERIC CORROSION 总被引：1，自引：0，他引：1
ImODUcrlONArnaorandnowincreasinglyimPoftantprobleminthemanyyearsinvestigationsofabosphericcormsionofmetaIsandalloyisthatthecormsionrmctionunderathineleCtrolytelayerchangessigwhcanhywithdrying.Tornashov(l966)reportedthatthecorm-sionrateisinfluentalbytheelamlytelayerthwhnessandiscontrolledbythedtheion-lndtingcurrentofoxygenreduCtionreig.l)whentheel~lytefilmisthickerthanthediffUSionlayerthickness.ThereforetherateisnotaffededbytheelCCtrolyteFilmthwh-nessforthecaseofaverythickFilm,e.g.regionI… 相似文献
6.
Heavy paint coating loss and localized corrosion of the Al alloy hull occur red after less than a year's service of a ship
at sea. Examination and analysis showed that the Mg-basic sacrificial anodes originally used for cathodic protection were
not suitable as the resulting −1.3V-plus (vs Ag/AgCl) protection potential for the hull was too negative for the purpose.
A new protection system was designed in which the protection current densities were 15mA/m2 for the hull and 350mA/m2 for the propeller. The hull protection potential under actual condition at sea was between −920mV and −1100mV (Ag/AgCl) and
the protection efficiency was over 90%. The protection areas were calculated by using the formulas A=1.8×LBP×D+BC×LB×B for
the hull and As=2Aas for the propeller.
Contribution No. 1640 from the Institute of Oceanology, Academia Sinica. 相似文献
7.
CORROSION AND ADHERENCE AT SEA OIL-PLATFORM 总被引：1，自引：0，他引：1
Measurements of the adhesive corrosion and protective potentials of 3 Bohai Sea oilplatforms under different cathodic protection showed corrosion still occurred on these platforms undertheir designed protective potentials. Preliminary conclusions from indoor experiments on the relation betweenadhesive corrosion and cathodic protection showed adhering organisms caused the corrosion onthese platforms. 相似文献
8.
Electrochemical reduction of dissolved oxygen in seawater on metals is of great importance for corrosion studies. The present paper studied cathodic reduction of dissolved oxygen on Q235 carbon steel in 3. 5% sodium chloride(NaCl)solutions by cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS), rotating disk electrode(RDE)and rotating ring-disk electrode(RRDE). The cyclic voltammetric results demonstrated the cathodic process on Q235 carbon steel in O2-saturated 3. 5% NaCl solution contains three reactions:dissolved oxygen reduction, iron oxides reduction and hydrogen evolution. The peak potential of oxygen reduction reaction(ORR)is-0. 85 V vs Ag/AgCl, 3 molL-1 KCl. The E1S results indicated that the ORR occurring on Q235 carbon steel is a 4-electron process and that no finite diffusion is caused by the intermediate of H2O2 produced by ORR. The RDE and RRDE voltammograms confirmed the EIS results and it was found that the number of transferred electrons for ORR was nearly 4, I. E. , dissolved oxygen reduced to water. 相似文献
9.
Laboratory and field tests on our newly developed embeddable reference electrode for reinforced concrete show it can be embedded
into reinforced concrete structures and be used for measuring the potentials of the rebar or other metal elements in the outer
structural part exposed to seawater. Its potential varies little with the change of Cl− concentration of the electrolyte and is stable over a time range of 260 days. The electrode can be used for monitoring corrosion
and cathodic protection of reinforced concrete structures in seawater.
Contribution No. 1605 from the Institute of Oceanology, Academia Sinica. 相似文献
10.
A study on the impedance responses of inhibitor desorption 总被引：1，自引：0，他引：1
王佳 《中国海洋湖沼学报》1998,16(1):54-59
INTRODUCTIONInhibit0rdesorptionfrequenhyresultSininstabilityandtheninvalidationoftheads0boiIiliibitorincertainanodicp0tenhalrangePraricV.J.andDradeD.M.,l99O,WangJiaetal.,l99l).InrenzandMansfeld(l98l)rePortedthattheinhibitordesorpti0ncouldproduceonthetheedancediagramaninductivelo0p,whichdePends0nthenabeoftheadd,theadditives,tirneandpotential.Sineeproonessuchasndldiss0lution,adsorph0nanddesorptionofinhibitorandotherreevantionsinteraCtwithcachother,theinhibitordesorpti0nbehaviorrnayprov… 相似文献
11.
INHIBITOR EFFECTS ON THE ANODIC BEHAVIOR OF IRON ELECTRODES 总被引：2，自引：0，他引：2
王佳 《中国海洋湖沼学报》1997,15(2):156-162
ImODUcrIONItisWellknownthatinmostcasesaninhibitorcanproteCmetaIsfromcorrosiononlybyforInjngonthemetalsuffoceanadsorbedinhibitor1ayerWhichisolatesthemetalfromthecorrosivemediumorchangesthecormsionreaCtionmeCanism,sothisadsorbedinhibitorlayer'sstabllityisboortantforinhibition.OIilyinhibitorswhichadsorbstabIyonmetalsurfacecanhaveexeellentperformance.ManyfaCtorscanaffedthestabilityoftheadsorbedinhibitorlayerfchdricalstrUc-tureoftheinhibitor,stateofmetalsurface,sortSandconcentrationoftherela… 相似文献
12.
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. 相似文献
13.
Dai Zhongdao 《中国海洋湖沼学报》1987,5(4):340-350
An anticorrosion method using wet DZ1 tape and electrochemical cathodic protection is suggested. The advantages of this method over internationally patented sealing
techniques lie in its electrochemically open system, high adsorption of OH− with resultant rise of pH, exchangeable electrolytes, simple pretreatment of the steel pipe, simplicity of application, lower
cost, better protection even under ebb tide, and low transmission of oxygen and corrosion products.
Contribution No. 1455 from the Institute of Oceanology, Academia Sinica 相似文献
14.
Steel piles at the tidal zone can be seriously corroded. Common protective methods such as painting or coating with rubber
or other protective materials, etc. cannot provide full protection when used as supplementary protection because these traditional
methods require strict pretreatment and sealing of the metallic surface from the corrosive mediums, and time for the protective
coatings to solidify. This is very difficult under the severe action of waves and surges on the sea.
With our oil-soluble DZ-2 tape, protection efficiency for hanging steel plates at the tidal and splash zones reaches to 82–99%.
The protection efficiency of water soluble DZ tape at the tidal zone reaches to 92.9%. The DZ and DZ-2 tapes can rapidly reduce
the original corrosion velocity to ten percent and one percent respectively as fully proved by the 500 hour rapid corrosion
testing with indoor salt fog and by the relevant electrochemical parameters of instantaneous corrosion velocity, etc.
DZ tape absorbs much OH− to cause a pH rise. A synergistic protective effect is gained when DZ tape is used together with cathodic protection of steel
piles at the tidal zone. The working principle of DZ tape is different from that of DZ-2 tape even though they are composed
of the same chemical materials. The latter provides protection because of the close affinity between metal and its carboxyl
group shields the active centre at the metal surface to reduce the activation energy of metal. The carbon chain forms a covering
oil film of netted structure.
Dai Tao, Dai Wei and Xia Caiyuan et al. participated in the research and made useful contribution. Contribution No. 1656 from
the Institute of Oceanology, Academia Sinica. 相似文献
15.
王佳 《中国海洋湖沼学报》1996,14(4):291-296
Electrochemical studies on the cathodic reaction of marine atmospheric corrosion using Kelvin probeas reference electrode showed that the rate of cathodic reaction-oxygen reduction first increases then de-creases, with the reaction maximizing at a certain thickness as the electrolyte film decreases duringevaporation. It was indicated that with decreasing electrolyte thickness by drying, the oxygen reduction ratewas accelerated by the faster oxygen diffusion due to the thinner electrolyte layer on the metal surface. Theresults also revealed that although the oxygen salting out effect has great influence on the rate of oxygenreduction, it is not the main causative factor for the decrease in cathodic limiting current in the case of avery thin electrolyte layer. 相似文献
16.
INTRODUCTIONBrownalgaepolyphenol (BAP)isadistinctivenaturalproduct,anactiveorganicmatterre leasedfromnormalgrowingbrownalgaeintoseawater.TheBAPoutputfromthelivingbrownalgaeis 1g (m2 ·d) (Craigieetal.,1 964 ) .About3 7%ofdissolvedorganicmatter(DOM)inseawateralongshoreisthesecretionfromseaweedcells,andcanreach 70 %oftotalDOMinseawaterifor ganicmatterreleasedbydeadalgaeisincluded (Raganetal.,1 979) .BAP (mainlycomprisingtheyellowmatter)inseawateralongshore ,canreach 2 .5mg L (Rashida… 相似文献
17.
首先经过理论推导得到有限圆柱体重力位三阶梯度张量（又称重力曲率张量）正演计算公式,之后依据所推导的理论公式进行模型实验,通过以下2个方面来验证所推导公式的正确性：1） 将理论计算公式与重力位梯度张量的中心差分结果进行模型实验对比;2） 根据拉普拉斯方程检验部分分量之和是否为零。 相似文献
18.
Prediction for potential landslide zones using seismic amplitude in Liwan gas field,northern South China Sea 总被引：1，自引：0，他引：1
Xishuang Li Baohua Liu Lejun Liu Jiewen Zheng Songwang Zhou Qingjie Zhou 《中国海洋大学学报(英文版)》2017,16(6):1035-1042
The Liwan (Lw) gas field located in the northern slope of the South China Sea (SCS) is extremely complex for its sea-floor topograghy, which is a huge challenge for the safety of subsea facilities. It is economically impractical to obtain parameters for risk assessment of slope stability through a large amount of sampling over the whole field. The linkage between soil shear strength and seabed peak amplitude derived from 2D/3D seismic data is helpful for understanding the regional slope-instability risk. In this paper, the relationships among seabed peak, acoustic impedance and shear strength of shallow soil in the study area were discussed based on statistical analysis results. We obtained a similar relationship to that obtained in other deep-water areas. There is a positive correlation between seabed peak amplitude and acoustic impedance and an exponential relationship between acoustic impedance and shear strength of sediment. The acoustic impedance is the key factor linking the seismic amplitude and shear strength. Infinite slope stability analysis results indicate the areas have a high potential of shallow landslide on slopes exceeding 15° when the thickness of loose sediments exceeds 8 m in the Lw gas field. Our prediction shows that they are mainly located in the heads and walls of submarine canyons. 相似文献
19.
诸暨璜山金矿是除治岭头以外浙江省第二金矿,它的找矿模式为"三高两低一复合"的找矿模式,即高金晕、高极化率、高磁场跳跃、低电阻率、低电位和北东断裂与北东东断裂复合处是成矿最有利部位.在其附近仍有类似成矿部位,有望扩大远景. 相似文献
20.
A rapid method of microwave assisted acid hydrolysis was established to prepare κ-carra-oligosaccharides. The optimal hydrolysis condition was determined by an orthogonal test. The degree of polymerization(DP) of oligosaccharides was detected by high performance thin layer chromatography(HPTLC) and polyacrylamide gel electrophoresis(PAGE). Considering the results of HPTLC and PAGE, the optimum condition of microwave assisted acid hydrolysis was determined. The concentration of κ-carrageenan was 5 mg m L-1; the reaction solution was adjusted to p H 3 with diluted hydrochloric acid; the solution was hydrolyzed under microwave irradiation at 100 for 15℃ min. Oligosaccharides were separated by a Superdex 30 column(2.6 cm × 90 cm) using AKTA Purifier UPC100 and detected with an online refractive index detector. Each fraction was characterized by electrospray ionization mass spectrometry(ESI-MS). The data showed that odd-numbered κ-carra-oligosaccharides with DP ranging from 3 to 21 could be obtained with this method, and the structures of the oligosaccharides were consistent with those obtained by traditional mild acid hydrolysis. The new method was more convenient, efficient and environment-friendly than traditional mild acid hydrolysis. Our results provided a useful reference for the preparation of oligosaccharides from other polysaccharides. 相似文献