Effects of Bi and Ti on electrochemical property of Al-Zn-In sacrificial anode

The effect of trace elements Bi and Ti on the electrochemical property of aluminium sacrificial anode in seawater was studied. Different amounts of Bi and Ti were alloyed with Al-Zn-In to make 9 types of aluminium sacrificial anodes. Anode closed circuit potential, discharge capacities and current efficiencies were measured in the laboratory. The results show that the effect of Bi is greater than that of Ti. Contribution No. 1869 from the Institute of Oceanology, Academia Sinica.     

ELECTROCHEMICAL BEHAVIOR OF Al-BASIC SACRIFICIAL ANODE AT ESTUARY

The Al-basic sacrificial anode is widely used to protect steel construction from corrosion in seawater,but is not suitable for protecting steel in freshwater. In the estuary area, seawater and freshwater mix anddifferent seawater salinity can be formed in different mixing sites between freshwater and seawater. Basedon the requirements of the Shengli Petroleum Administrative Bureau of China, the effect of seawatersalinity on electrochemical properties of Al-basic anode was studied under laboratory conditions by themethod given in National Standard GB 4948-85 (China Starndard Bureau, 1985). No obvious effectwas found when seawater salinity was 30 to 10, but obvious effect on anodic open circuit potential, closedcircuit potential and current efficiency was found when seawater salinity was 5. These values are lowerthan those given in the Naional Standard.     

Zn's role in dissolution of al sacrificial anodes

The role of alloying elements in the dissolution of aluminium sacrificial anodes was investigated. The effect of indium on the electrochemical performance of anode and the relationship between indium and impurities, such as silicon and iron, were studied. The distribution of indium in aluminium alloy was detected. The electrochemical behaviour of In-implanted aluminium alloy was also studied. The experimental results indicate that indium activates the surface of aluminium alloy and improves the electrochemical performance of alloy containing more amounts of impurity. Indium combines with silicon and iron. More satisfactory properties were obtained when the alloy's proportion of content of In to that of (Si+Fe) is about 1∶(8∼10). The electrochemical properties of Al alloy, especially the surface activity of the anode were improved by ion implantation. Indium segregates in the alloy. The amount of Si and Fe in the In-rich segregated phase is richer than that in the matrix. It is proposed that the In-rich segregated phase particles activate the surface and promote the dissolution process of the aluminium sacrificial anode.     

Electrochemical behavior of Al—basic sacrificial anode at estuary

The Al—basic sacrificial anode is widely used to protect steel construction from corrosion in seawater, but is not suitable for protecting steel in freshwater. In the estuary area, seawater and freshwater mix and different seawater salinity can be formed in different mixing sites between freshwater and seawater. Based on the requirements of the Shengli Petroleum Administrative Bureau of China, the effect of seawater salinity on electrochemical properties of Al—basic anode was studied under laboratory conditions by the method given in National Standard GB 4948-85 (China Starndard Bureau, 1985). No obvious effect was found when seawater salinity was 30 to 10, but obvious effect on anodic open circuit potential, closed circuit potential and current efficiency was found when seawater salinity was 5. These values are lower than those given in the National Standard. Contribution No. 2681 from the Institute of Oceanology, Chinese Academy of Sciences. This study is a major project (Ky85-11-5) and a key project (A14920416) of the Chinese Academy of Sciences, and also received support from the Shengli Oil Field.     

The influence of the corrosion product layer generated on the high strength low-alloy steels welded by underwater wet welding with stainless steel electrodes in seawater

The high strength low-alloy steels are welded by underwater wet welding with stainless steel electrodes. The micro-structural and electrochemical corrosion study of base metal (BM), weld zone (WZ) and heat affected zone (HAZ) are carried out to understand the influence of the corrosion product layer generated on the high strength low-alloy steels welded by underwater wet welding with stainless steel electrodes, methods used including, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM). The results indicate that the WZ acts as a cathode and there is no corrosion product on it throughout the immersion period in seawater. The HAZ and BM acts as anodes. The corrosion rates of the HAZ and BM change with the immersion time increasing. In the initial immersion period, the HAZ has the highest corrosion rate because it has a coarse tempered martensite structure and the BM exhibites a microstructure with very fine grains of ferrite and pearlite. After a period of immersion, the BM has the highest corrosion rate. The reason is that the corrosion product layer on the HAZ is dense and has a better protective property while that on the BM is loose and can not inhibit the diffusion of oxygen.     

Comparative study of two carbon fiber cathodes and theoretical analysis in microbial fuel cells on ocean floor

Cathode activity plays an important role in the improvement of the microbial fuel cells on ocean floor(BMFCs). A comparison study between Rayon-based(CF-R) and PAN-based carbon fiber(CF-P) cathodes is conducted in the paper. The two carbon fibers were heat treated to improve cell performance(CF-R-H CF-P-H), and were used to build a new BMFCs structure with a foamy carbon anode. The maximum power density was 112.42 mW m-for CF-R-H, followed by 66.6 mW m-2 for CF-R, 49.7 mW m-2 for CF-P-H and 21.6 mW m-2 for CF-P respectively. The higher specific area and deep groove make CF-R have a better power output than with CF-P. Meanwhile, heat treatment of carbon fiber can improve cell power, nearly two-fold higher than heat treatment of plain fiber. This improvement may be due to the quinones group formation to accelerate the reduction of oxygen and electron transfer on the fiber surface in the three phase boundary after heat treatment. Compared to PAN-based carbon fiber, Rayon-based carbon fiber would be preferentially selected as cathode in novel BMFCs design due to its high surface area, low cost and higher power. The comparison research is significant for cathode material selection and cell design.     

Electrochemical properties of electrodes with different shapes and diffusion kinetic analysis of microbial fuel cells on ocean floor

Microbial fuel cell(MFC) on the ocean floor is a kind of novel energy-harvesting device that can be developed to drive small instruments to work continuously.The shape of electrode has a great effect on the performance of the MFC.In this paper,several shapes of electrode and cell structure were designed,and their performance in MFC were compared in pairs:Mesh(cell-1) vs.flat plate(cell-2),branch(cell-3) vs.cylinder(cell-4),and forest(cell-5) vs.disk(cell-6) FC.Our results showed that the maximum power densities were 16.50,14.20,19.30,15.00,14.64,and 9.95 mWm-2 for cell-1,2,3,4,5 and 6 respectively.And the corre-sponding diffusion-limited currents were 7.16,2.80,18.86,10.50,18.00,and 6.900 mA.The mesh and branch anodes showed higher power densities and much higher diffusion-limited currents than the flat plate and the cylinder anodes respectively due to the low diffusion hindrance with the former anodes.The forest cathode improved by 47% of the power density and by 161% of diffusion-limited current than the disk cathode due to the former’s extended solid/liquid/gas three-phase boundary.These results indicated that the shape of electrode is a major parameter that determining the diffusion-limited current of an MFC,and the differences in the elec-trode shape lead to the differences in cell performance.These results would be useful for MFC structure design in practical applica-tions.     

Humic Acid and Iron Chelation Modified Anode Improves the Electrochemical Performance of Marine Sediment Microbial Fuel Cell

Marine sediment microbial fuel cell(MSMFCs)can be utilized as a long lasting power source to drive small instruments to work for long time on ocean floor and its higher power has a significant meaning for practical application.Anode modification can greatly improve the performance of MSMFCs.Herein,humic acid(HA)and humic acid-iron ion complex(HA-Fe)were used to modify the anode for constructing a better MSMFCs.The results indicated that HA-Fe modified anode,better than HA modification,significantly improved the MSMFCs cell power output.The maximum power density of HA-Fe modified MSMFCs is 165.3 mW m?2,which are 6.5-folds of blank MSMFCs.The number of microorganisms on anode,redox activity,and relative kinetic activity were 1.8-,6.1-,and 13.1-folds of blank MSMFCs,respectively.The MSMFCs improvement would be attributed to the electron transfer media of HA and the valence conversion of Fe ions.A synergistic interaction between the naturally occurring HA and Fe ions on the anodic surface in marine sediments would make the modified anodes have‘renewable’characteristics,which is beneficial for the MSMFCs to maintain its long-term higher power.     

EFFECT OF SULPHATE-REDUCING BACTERIA ON ELECTRO-CHEMICAL CORROSION BEHAVIOR OF 16Mn STEEL IN SEA MUD

ＩＮＴＲＯＤＵＣＴＩＯＮＩｔｗａｓｇｅｎｅｒａｌｌｙｃｏｎｓｉｄｅｒｅｄｐｒｅｖｉｏｕｓｌｙｔｈａｔｔｈｅｃｏｒｒｏｓｉｏｎｏｆｓｔｅｅｌｉｎｓｅａｍｕｄｗａｓｎｏｔｓｅｒｉｏｕｓ.Ｈｏｗｅｖｅｒ,ｉｔｗａｓｌａｔｅｒｆｏｕｎｄｔｈａｔｔｈｅｃｏｒｒｏｓｉｏｎｒａｔｅｏｆｓｔｅｅｌｉｎｓｏｍｅｓｅａｍｕｄｗａｓｈｉｇｈｅｒｔｈａｎｔｈａｔｉｎｓｅａｗａｔｅｒ(Ｋｉｎｇ,1980;Ｓｅｈｍｉｄｅ,1982;Ｇｕｏｅｔａｌ.,1997;Ｈｏｕ,1998).Ｔｈｅｒｅａｒｅｓｏｍｅｒｅｐｏｒｔｓｔｈａｔｔｈｅｃｏｒｒｏｓｉｏｎｒ…     

Influence of dissolved oxygen on the protectiveness and morphological characteristics of calcareous deposits with galvanostatic polarization

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.     

Cathodic protection of A1 hull ship

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 A_s=2Aa_s for the propeller. Contribution No. 1640 from the Institute of Oceanology, Academia Sinica.     

Electrochemical evaluation of dissolution characteristics of Al-based sacrificial anodes in seawater

The surface dissolution characteristics of Al-based sacrificial anodes in seawater have never been expressed numerically except in words such as uniform dissolution, non-uniform dissolution, serious localized dissolution, etc. An electrochemical method was developed in our laboratory to evaluate the above mentioned characteristics quantitatively. The Al anode samples are polarized to −1000 mv (vs. Ag/AgCl reference electrode) in seawater at 25±1°C, and anodic current-time curves are recorded simultaneously. Then the coulometric density was calculated with the aid of a planimeter. By comparing the coulometric densities of these samples, the surface dissolution characteristics of anodes can be evaluated quantitatively. Contribution No. 1447 from Institute of Oceanology, Academia Sinica     

Electrochemical measurement of steel corrosion in seabottom sediment with “MD” method

The through one year corrosion potential and polarization resistance for 3 kinds of steels in seabottom sediment of Liaodong Bay were measured with the “MD” method. The measurements will have some theoretical and practical values. The theoretical value lies in that the recorded changing process of the practical corrosion case can be basis for indoor discussion and electrochemical research on the corrosion process. The practical value lies in that the obtained data can be basis for designing and controlling electrochemical protection systems. In fact, it is very difficult to measure in situ the corrosion parameters of steels in sea sediment. Contribution No. 2611 from the Institute of Oceanology, Chinese Academy of Sciences. This study is a major project of the Chinese Academy of Sciences.     

ELECTROCHEMICAL MEASUREMENT OF STEEL CORROSION IN SEABOTTOM SEDIMENT WITH “MD” METHOD

The tbough one year cormsion potential and polarisation resistanoc for 3 kinds of stals in seabottomedment of Liaodong Bay were measured with the “MD” method.The measurements wiIl have some thoretical and pndital talues. The thooretical valoc lies in thatthe reoorded changing process of the practital corrosion case can be basis for indoor discussion andeectrochemical on the corrosion practical value lies in that the obtained datu canbe basis for designing and controlling elatrochemical protation syttems. In fact, it is very difficult tomeasure in situ the cornosion parnders of steeIs in sea sediment.     

Simulation Study of Potential Impacts of Tidal Farm in the Eastern Waters of Chengshan Cape,China

The sea area east of Chenshan Cape has peak tidal current flows that exceed 2.3 m s-1, which make it a promising site for the development of tidal current energy. Before these resources can be exploited, a comprehensive assessment is needed of the potential environmental impacts of the extraction of this energy. In this paper, we describe our construction of a three-dimensional hydrodynamic model of the waters near Chengshan Cape, and verify the performance of the model using continuous data measured in situ. We modeled the potential impacts of the exploitation of these resources on the flow field by adding a momentum loss term in the governing equation of the model. Simulation results show that an assumed tidal farm with an estimated power output of 20.34 MW would have a significant impact on the surrounding water level, especially next to the farm, where fluctuation could reach 6 cm. The maximum drop in the flow velocity in the wake of the farm was predicted to be more than 0.8 m s-1, and this influence would extend 10 km downstream.     

INHIBITOR EFFECTS ON THE ANODIC BEHAVIOR OF IRON ELECTRODES

ImODUcrIONItisWellknownthatinmostcasesaninhibitorcanproteCmetaIsfromcorrosiononlybyforInjngonthemetalsuffoceanadsorbedinhibitor1ayerWhichisolatesthemetalfromthecorrosivemediumorchangesthecormsionreaCtionmeCanism,sothisadsorbedinhibitorlayer'sstabllityisboortantforinhibition.OIilyinhibitorswhichadsorbstabIyonmetalsurfacecanhaveexeellentperformance.ManyfaCtorscanaffedthestabilityoftheadsorbedinhibitorlayerfchdricalstrUc-tureoftheinhibitor,stateofmetalsurface,sortSandconcentrationoftherela…     

Measurements of sea ice thickness and its subice morphology analysis using ice-penetration radar in the Arctic Ocean

1　IntroductionSeaice ,asanimportantcomponentoftheArcticclimatesystem ,hasdrawnsignifi cantscientificinterest.Seaicethicknessanditsmorphologyhavedramaticimpactsono cean atmosphere iceinteractions(Wadhams 1 994;Barryetal.1 993 ;Dickson 1 999;PadhamsandNorman 2 0 0 0 ) ,whichdirectlyaffecttheexchangeprocessandspeedofheatandmassbetweentheoceanandtheatmosphere ,dominatethephysicalmechanicsfea turesofseaice ,andaffecttheseaicemovement&deformationaswellasicefreezing&meltingprocess(Hollandetal.1 99…     

Effects of temperature, algae biomass and ambient nutrient on the absorption of dissolved nitrogen and phosphate by Rhodophyte Gracilaria asiatica

Gracilaria asiatica,being highly efficient in nutrient absorption,is cultivated in sea cucumber ponds to remove nutrients such as nitrogen and phosphate.It was cultured in a laboratory simulating field conditions,and its nutrient absorption was measured to evaluate effects of environmental conditions.Ammonia nitrogen(AN),nitrate nitrogen(NN),total inorganic nitrogen(TIN),and soluble reactive phosphorus(SRP) uptake rate and removal efficiency were determined in a 4×2 factorial design experiment in water temperatures(T) at 15℃ and 25℃,algae biomass(AB) at 0.5 g/L and 1.0 g/L,total inorganic nitrogen(TIN) at 30 μmol/L and 60 μmol/L,and soluble reactive phosphorus(SRP) at 3 and 6 μmol/L.AB and ambient TIN or SRP levels significantly affected uptake rate and removal efficiency of AN,NN,TIN,and SRP(P<0.001).G.asiatica in AB of 0.5 g/L showed higher uptake rate and lower removal efficiency relative to that with AB of 1.0 g/L.Nitrogen and phosphorus uptake rate rose with increasing ambient nutrient concentrations;nutrient removal efficiency decreased at higher environmental nutrient concentrations.The algae preferred to absorb AN to NN.Uptake rates of AN,NN,and SRP were significantly affected by temperature(P<0.001);uptake rate was higher for the 25℃ group than for the 15℃ group at the initial experiment stage.Only the removal efficiency of AN and SRP showed a significant difference between the two temperature groups(P<0.01).The four factors had significant interactive effects on absorption of N and P,implying that G.asiatica has great bioremedial potential in sea cucumber culture ponds.     

三元复合驱采油污水阻垢缓蚀剂电化学分析

研制适用于三元复合驱采油污水工况条件下的MPM固体缓蚀阻垢剂,分析三元复合驱采油污水中MPM的电化学特性.结果表明:随着温度增加,20#钢在采油污水的腐蚀速率呈增加趋势,极化曲线显示钝化区表面材料在表面高温下处于钝化状态,产生的钝化膜能够降低腐蚀速度.在阻垢缓蚀剂质量浓度相同的情况下,不同温度的电化学阻抗谱在高频区出现容抗弧,显示优良的缓蚀性能.不同质量浓度MPM极化曲线表明,缓蚀率随MPM质量浓度的增加而增大,MPM极值质量浓度为80mg/L.污水体系中的Ca2+、Cl-对缓蚀率产生影响.MPM适用于高质量浓度Ca2+的三元复合驱采油污水处理.     

A Gaussian process regression-based sea surface temperature interpolation algorithm

The resolution of ocean reanalysis datasets is generally low because of the limited resolution of their associated numerical models.Low-resolution ocean reanalysis datasets are therefore usually interpolated to provide an initial or boundary field for higher-resolution regional ocean models.However,traditional interpolation methods(nearest neighbor interpolation,bilinear interpolation,and bicubic interpolation) lack physical constraints and can generate significant errors at land-sea boundarie s and around islands.In this paper,a machine learning method is used to design an interpolation algorithm based on Gaussian process regression.The method uses a multiscale kernel function to process two-dimensional space meteorological ocean processes and introduces multiscale physical feature information(sea surface wind stress,sea surface heat flux,and ocean current velocity).This greatly improves the spatial resolution of ocean features and the interpolation accuracy.The effectiveness of the algorithm was validated through interpolation experiments relating to sea surface temperature(SST).The root mean square error(RMSE)of the interpolation algorithm was 38.9%,43.7%,and 62.4% lower than that of bilinear interpolation,bicubic interpolation,and nearest neighbor interpolation,respectively.The interpolation accuracy was also significantly better in offshore area and around islands.The algorithm has an acceptable runtime cost and good temporal and spatial generalizability.