STUDY ON THE CORROSION PEAK OF CARBON STEEL IN MARINE SPLASH ZONE

lNTRODUCTI0NSincetheoonceptofrnarinesplashzone(MSZ)wasfirstproposedbyHumble,rnanyresearchesprovedthatthecorrosionofsteelinthesplashzoneisthemostseriousinthemarineenvironninetandthatthisMSZcorrosionhasapeak(Zhu,l995).Howevertheenvironmentalfactorscatisingthecorrosionpeakwasnotkn0wnthen(Niat0,l975,Atsushi,l994)andtherangeoftheMSZwasnotyetdeariydefinedopzkaki,l985).ThispaperexplainsthemaincauseofthecormsionpeakanddefinestheexaCtrangeoftheMSZinsomeofChina'sharbours.MATERIALSANDMET…     

Simulation test apparatus for marine corrosion

ＩＮＴＲＯＤＵＣＴＩＯＮＳｔｅｅｌｃｏｎｓｔｒｕｃｔｕｒｅｓａｒｅｓｅｖｅｒｅｌｙｃｏｒｒｏｄｅｄｉｎｍａｒｉｎｅｅｎｖｉｒｏｎｍｅｎｔｇｅｎｅｒａｌｌｙｄｉｖｉｄｅｄｉｎｔｏ5ｃｏｒｒｏｓｉｏｎｚｏｎｅｓｉｎａｃｃｏｒｄａｎｃｅｗｉｔｈｔｈｅｃｏｒｒｏｓｉｏｎｂｅｈａｖｉｏｒｏｆｓｔｅｅｌａｔｓｅａ:ｍａｒｉｎｅａｔｍｏｓｐｈｅｒｉｃｚｏｎｅ,ｓｐｌａｓｈｚｏｎｅ,ｔｉｄａｌｚｏｎｅ,ｓｅａｗａｔｅｒｚｏｎｅａｎｄｓｅａｍｕｄｚｏｎｅｓ.Ｐｒｏｔｅｃｔｉｖｅｍｅａｓｕｒｅｓｆｏｒｔｈｅｓｅｃｏｒｒｏ…     

Study on rust layers on steel in different marine corrosion zone

IrmODUCnONTheMossbaureffect(ME)isalsoknOWnasrecoil-thenuclearresonaneabsorp-hon.MossbaursPeCboscoPy(MS)haspIDvedtobeaveryuSefultecheqUeforstudytngcormsionPimessesandcedon-cts.TheInainadvantagsofMSincormsionre-enhare:(l)thenon-deStrutivechateroftheteCboqUe;(2)possibilltyforquali-tativeandqUanitativephaanalsis;(3)uSehassinidenificationofPOOrlycrystal-lizedoramorphouscormsionpnhats.WththedeVfoPmntofInarineresomees,InansteelconstrUctionswerebulltatsea'MSwasusedforanalfongcormsion~t…     

ELECTROCHEMICAL STUDIES ON THE CATHODIC REACTION OF MARINE ATMOSPHERIC CORROSION

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.     

ELECTROCHEMICAL MEASUREMENTS FOR MARINE ATMOSPHERIC CORROSION STUDIES USING KELVIN PROBE REFERENCE ELECTRODE

A Kelvin probe was used as reference in this study on electrochemical measurements of a simulatedmarine atmospheric corrosion system (electrode covered by a very thin electrolyte layer). The experimentalsetups for improved measurements proved satisfactory for the conventional steady-state electrochemicalmeasurements in atmospheric studies.     

Methods used to study bacterial diversity in the marine environment around Qingdao

Pollution has a considerable effect on biological communities, in terms of size and diversity of the populations. Yet, the precise consequences of human activity on microbial communities in the marine environment are poorly understood. Therefore, in an ongoing collaborative research programme between Heriot-Watt University and the Ocean University of Qingdao, bacteria were isolated in 1999 and 2000 from marine sediment, seawater, seaweed, fish and shellfish, taken from locations in Shandong Province adjacent to Qingdao. Sampling locations were comprised of industrial and aquacultural sites and a clean, control site. In order to analyse microbial diversity, a polyphasic approach was adopted for characterisation of these isolates, specifically through examination of key phenotypic traits, i.e. using Biolog GN MicroPlate^™ profiles, bacterial whole cell protein profiles and 16S and 23S rRNA gene sequences. These techniques yielded complex taxonomic data, which were subjected to statistical and cluster analyses. The application of these methods to studies of microbial communities is discussed.     

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.     

Heavy metal content in coral reef sediments from Red Sea of Yemen and its significance on marine environment

In order to determine and assess the concentrations of trace elements in coral reefs sediments from Red Sea of Yemen, sediment samples were collected, treated and analyzed for cadmium, chromium, cobalt, copper, manganese, nickel, iead, iron, zinc and vanadium by the atomic absorption spectrometric analysis. The result is that cadmium, cobalt and lead concentrations were high and other elements are low or the same as natural background. It is concluded that the high cadmium, cobalt and lead levels in coral reefs sediments will have negative effects on marine life of the sites, so further researches are needed to characterize the sources fate, biogeochemical processes and impacts of these trace elements on coral reefs and marine of the region.     

Heavy metal content in coral reef sediments from Red Sea of Yemen and its significance on marine environment

In order to determine and assess the concentrations of trace elements in coral reefs sediments from Red Sea of Yemen, sediment samples were collected, treated and analyzed for cadmium, chromium, cobalt, copper, manganese, nickel, lead, iron, zinc and vanadium by the atomic absorption spectrometric analysis. The result is that cadmium, cobalt and lead concentrations were high and other elements are low or the same as natural background. It is concluded that the high cadmium, cobalt and lead levels in coral reefs sediments will have negative effects on marine life of the sites, so further researches are needed to characterize the sources fate, biogeochemical processes and impacts of these trace elements on coral reefs and marine of the region.     

Influence of active marine organic matter on electrochemical corrosion

Chemical means were used to extract polyphenols from healthy brown algae collected in littoral seawater. Experiments on corrosion of A₃ steel, the time-potential curve, and polarization curve in polyphenols seawater showed stronger cathodic polarization compared with that in common seawater. This indicates that brown algae polyphenols might feasibly be used as corrosion inhibitor in seawater. Contribution No. 3763 from the Institute of Oceanology, Chinese Academy of Sciences. Project 59471054 supported by NSFC and National “Nineth Five Year” Project 96-916-04-01.     

Evaluation of long-term corrosion durability and self-healing ability of scratched coating systems on carbon steel in a marine environment

Defects in protective-coating systems on steel surfaces are inevitable in practical engineering applications.A composite coating system,including a primer,middle coat and topcoat,were used to protect carbon steel from corrosion in a marine environment.Two environmental additives,glass fi bers and thiourea,were applied in the middle coat to modify the coating system.The long-term corrosion durability and self-healing ability of the scratched coating system were evaluated by multiple methods.Results of the electrochemical technologies indicated that the coating system that contained 0.5 wt.%fi bers and 0.5 wt.%thiourea presented good corrosion protection and self-healing for carbon steel when immersed in 3.5%Na Cl for 120 d.Evolution of localized corrosion factors with time,as obtained from the current distribution showed that fi bers combined with thiourea could inhibit the occurrence of local corrosion in scratched coating systems and retarded the corrosion development signifi cantly.Surface characterization suggested that adequate thiourea could be absorbed uniformly on fi bers for a long time to play an important role in protecting the carbon steel.Finally,schematic models were established to demonstrate the action of fi bers and thiourea on the exposed surface of the carbon steel and the scratched coating system in the entire deterioration process.     

CHARACTERISTICS OF THE OXYGEN REDUCTIONIN ATMOSPHERIC CORROSION

ImODUcrlONArnaorandnowincreasinglyimPoftantprobleminthemanyyearsinvestigationsofabosphericcormsionofmetaIsandalloyisthatthecormsionrmctionunderathineleCtrolytelayerchangessigwhcanhywithdrying.Tornashov(l966)reportedthatthecorm-sionrateisinfluentalbytheelamlytelayerthwhnessandiscontrolledbythedtheion-lndtingcurrentofoxygenreduCtionreig.l)whentheel~lytefilmisthickerthanthediffUSionlayerthickness.ThereforetherateisnotaffededbytheelCCtrolyteFilmthwh-nessforthecaseofaverythickFilm,e.g.regionI…     

STRESS CORROSION CRACKING OF AISI 321 STAINLESS STEEL IN ACIDIC SEAWATER

ImooUonONSCCisoneofthemosttwortantcausoffailureofstaiuleSsstalequipmentandfacilitieS.Studiesonunh0refacilitiesshowedthatanaddicchloridesolutionfilmcouldbefo~onthescheeofstalandthatstaiuleSSstalisinaCtivedissolutionstateinaedicchloridesolutionopinetal.,l99O;Gnanamoorthyetal.,l99O).ltisgenerallythoughtxthatSCCcannotoimrwhenthematerialisinaCtiveanodicdissolutionstate,soitsomcewithresultingcasualties(0ldfieldetal.,l99O)arousedattentiont0it.SomeSCCmeCanisrnsproposedpeuang,l988,Newmanctal.,…     

CORROSION RESISTANCE OF INTERFERENCE FILM ON STAINLESS STEEL

IwrRODUcrlONStainlessstalhasbeenusedwidelyasbuildingrnateria1,especiallyasdecoratingrnate-rialinbuildings.Ordinarystainlesssteehasonlyonemonot0noussilverywhitCcolourwhichsomeimesdoesnotrnatchwithitSsurmundingenvironment.lnordert0improveitSdereratingperfonnaneeandexpanditsuse,muchresearchhasbeenconductedsincethe4O'st0trytoformabright,uniform,highcorrosi0nandwearresistantco1ourfilmonastainlesssteesurface.Duringtheeariystage,anirnmersionedhodwasused,i.e.inimrs-ingthestainlesssteelinahots0luti…     

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…     

Implementing marine XML for observed CTD data in a marine data exchange platform

In order to archive,quality control and disseminate a large variety of marine data in a marine data exchange platform,a marine XML has been developed to encapsulate marine data,which provides an efficient means to store,transfer and display marine data.This paper first presents the details of the main marine XML elements and then gives an example showing how to transform CTD-observed data into Marine XML format,which illustrates the XML encapsulation process of marine observed data.     

基于应力腐蚀和腐蚀疲劳的焊缝磁记忆信号分析

为了研究不同腐蚀条件下的焊缝磁记忆特征信号,对20号钢板状焊缝试件进行残余应力腐蚀、35kN恒拉伸应力腐蚀和35kN静载、25kN动载拉拉腐蚀疲劳对比实验,分析焊缝正、反面磁记忆信号的变化规律,获得焊缝腐蚀发展进程中应力腐蚀与腐蚀疲劳各自对应的磁记忆特征信号.结果表明:在应力腐蚀状态下,不同拉伸载荷对应的磁记忆信号特征不同,35kN恒拉伸应力腐蚀与残余应力腐蚀相比,焊缝区磁记忆信号峰峰值及其梯度更大,磁记忆曲线分布的分散度更大;35kN静载、25kN动载拉拉腐蚀疲劳与35kN恒拉伸应力腐蚀相比,焊缝区磁记忆曲线上下波动多,过零点次数多,磁记忆曲线分布的分散度小.这为磁记忆技术在焊缝工程检测的定性与定量分析提供基础数据.     

ELECTROCHEMICAL CORROSION BEHAVIOR OF STEEL IN THE JUNCTURE AREA OF SEA CLAY AND SAND

Corrosion behavior of steel in the juncture area of sea clay and sand was studied. The results show that galvanic corrosion occurred between steel samples buried in sea clay and sand, and that the polarity of the galvanic cell reversed after some testing later. The cause of reversing of polarity is discussed.     

THE USE OF GRAIN SIZE TRENDS IN MARINE SEDIMENT DYNAMICS： A REVIEW

Spatial changes in grain size parameters (i. e. grain size trends) contain information on sediment transport patterns. An analytical procedure has been proposed to transform the grain size trends into an image of trend vectors, which may represent net sediment lransport pathways. A fundamental assumption for such an approach is that the frequency of occurrence of the trend adopted is much higher in the transport direction, than in any of other directions. Preliminary studies show agreement between this assumption and observations. However, further investigations into the physical processes and mechanisms for the formation of grain size trends are required to improve the technique, including flume experiments and numerical modeling. Moreover, attention should be paid to the trends associated with finegrained sediment, for the method of grain size trend analysis is so far designed for coarse-grained material only. The processes of flocculation during settling and the wash-load property must be considered. Appropriate interpretation of grain size data will improve our understanding of the physics of granular materials.     

Impedance characteristics of carbon steel under cathodic protection

INTRODUCTIONInpraCticalengineeringapplicati0ns,thecormsionofstalundercathodicprotalioncanbecontr0llediftheproodi0np0tenhalisset2O()t03(X)mVnegativewithaspeCttothenatamlcormsi0np0tenial(MasatSugi,l976,Takehiko,l972).Theprotalnp0tentia1edinpraedcalapplicationisbedonexperienceandtheory.Tooru(l985,l986)foundthattheopbocathodicproodionpotentialcoinddedwiththepotentialwhenpolarhati0nresistancemaxndnd,s0thiscoinedencecanbeedt00btainoptbore-sultforcarbonstalundercathodicpronaion.Inthiswork,the…