Abstract: The effects of 5% Al and 10% Al on the sulfidation behaviour of the Fe-25Cr alloy in H2S-H2 gas mixtures in the temperature range of 700~900℃ has been studied.The sulfidation resistance of Fe-25Cr was improved and sulfide scale morphologies,composition and structure of Fe-25Cr were changed remarkably.The sulfidation kinetics of the alloys with aluminium obeyed basically the parabolic law after an initial period of reaction time.The sulfidation mechanism of the Fe-Cr-Al alloy has been proposed.
Abstract: The cracking and break up of some common oxide scales on the iron-base alloys during their oxidation at a constant temperature and in the subsequent cooling process has been studied by means of an acoustic emission(AE) technique.The time dependence of the accumulation counts and the temperature were obtained.The phase species of oxide scales on the tested alloys were determined by a microscope,a scanning microscope and especially the X-ray diffraction analysis.It can be stated from the experimental results that the oxide scales on alloys cracked and broke up during the cooling process except for the oxide scale on the alloy containing silicon which cracked in the period of the constant temperature oxidation.The α-Al2O3 scale on Fe-25Cr-10Al cracked and exfoliated most severly.The total counts of AE of the Cr2O3 scale on the Fe-25Cr-7.5Nb alloy is much higher than that of Fe-25Cr.The situations of Fe-25-Cr-4Ti and Fe-25Cr-9Mn alloys were similar to that of Fe-25Cr.
Abstract: The stress corrosion cracking of 304SS weldments in NaCl solutions has been shudied by SSRT technique.It was found that there exists a critical temperature for the SCC in this system.The cirtical temperature decreases with the increase of NaCl concentration when the concentration of NaCl is lower than 1.0mol/L, but it doesn't change much in a wide range of NaCl concentration when the concentration of NaCl is higher than 1.0mol/L.The diagram of T(℃)-[Cl-]-SCC has been given.For the weldment,SCC occurs in weld fusion zone and propagates along δ-ferrite phase between austenite dendrites.
Abstract: The effect of Mo on the susceptibility to SCC of the low alloy steels in nitrate solutions has been studied by SSRT technique on the background of the intergranular stress corrosion cracking at high temperature.The addition of Mo to the alloy steel is favorable for the transformation of ferrite to bainite and/or pearlite and the latters are more resistant to SCC than the former.The diagram of "temperature-Mo content-SCC" of the system "low alloy steels/nitrate solutions" is proposed.
Abstract: The corrosion behavior of Cu and SS304 has been studied by means of the immersing test and the electrochemistry method under the conditions simulating industrial site.The influences of medium condition,particularly periodic cathodic state on material corrosion have been investigated.The reason and mechanism of corrosion failure of the conductor rolls have been proposed.
Abstract: The chemical stability of Zn-Ni alloy coating containing 12%~13% Ni is further improved in this paper by means of a new chromation process and its corrosion resistance is five times higher than unchromation one.The effects of the composition of chromate solution and operation conditions on formed mechanism of conversion coating were investigated,and the protective mechanism of the coating was also discussed.
Abstract: The influences of trace elements Cu,Fe,Cr on high speed Zn-Ni alloy electroplating and their mechanism have been investigated.The Cu2+ in Zn-Ni electrolyte can easily deposit,but it is a harmful element;while Fe2+ and Cr3+ are difficult to deposit.The Fe and Cr in deposit can increase the corrosion resistance of Zn-Ni deposit.The electrodepositing mechanism of trace elements has been discussed,and the quantitative predication method for wheather trace element can deposit from electrolyte has been established.
Abstract: The effects of complexes on the content and contribution of P element,morphology and corrosion resistance of electroless Ni-P alloy coating have been investigated.The results,obtained by immersion test,SEM observation after corrosion test and EDS composition analysis,showed that corrosion resistance of the coating depends on the P content in the coating,and associated with the surface morphology of coating and variation of P content.Further analysis indicated that all of these discussed above are related to the kind of complex selected.
Abstract: A set of film fracture apparatus has been designed on the basis of traditional scratching electrode experiment theory.The advantage of the film fracture method for passivation process study consists in the simultaneous exposing of the bare surface into solution,therefore the accurtate current decay relationship resulting from the passivation can be measured.The passivation process in 3.5% NaCl solution of the magnetron-sputtered amorphous and crystalline stainless steel film have been studied by use of the apparatus. The results showed that the bare surface of the amorphous film exhibited a higher reactivity and a more rapid formation rate of passive layer compared with the crystalline film.
Abstract: Effect of physical parameters(scratching time and scratching velocity) during the scratching process on the maxium reaction current of bare surface has been discussed in detail. Analysis results indicate that the maxium reaction current of bare surface varies as the scratching time or velocity changes.This kind of variation would make the decay parameter of repassivation kinetics distort.So the traditional scratch method is not able to investigate quantitalively the repassivation process of metals.
Abstract: The susceptibility of AISI 304L austenitic stainless steel to intergranular attack mainly caused by the Cr-depletion in grain boundaries was detected by the square-wave potentiostatic pulse technique. The degree of the sensitization of 304L stainless steel can be exactly and quantitively illustrated by this technique.The maximum reactivation current density corresponding to 10th pulse,ir10,was selected as a characteristic parameter for the detection of sensitization.The degree of the sensitization determined by square-wave potentiostatic pulse technique was in agreement with those obtained from DL-EPR and ASTM standard tests.
Abstract: The behaviour and mechanism of the oxygen concentration difference macrocell were investigated for steel A3 in the 3.5% NaCl solution by the self-made equipment.Three kinds of macrocell:O2/N2,O2/air,N2/air macrocells were formed.The ig~t,Eg~t curves were recorded in the experiments.The coefficient of the macrocell corrosion effect, r=iaA/ikA, was proposed for calculation of the effect intensity of macrocell.The results show that the effect behavior of these macorcells was the same,and all macrocells accelerated the corrosion rate of the anodic metal in macrocells.The correlation between the value of coefficient r and the real intensity of macrocell was testified to be relatively satisfactory.
Abstract: Distortion in the crystal lattice of 304L and 316L austenitic stainless steels resulted from charging hydrogen is researched by means of X-ray diffractometer.Austenitic lattice expansion-contraction-expansion caused by charging hydrogen is found and its possible mechanisms are discussed.
Abstract: This paper introduces the designing ideas,the system structures,the database structure and the system functions for the nature environment corrosion database system of common materials.A million and more data will be collected,arranged and stored in the database, which are the nature environment(atmospheric,marine,soil) corrosion data of six major kinds of common materials:ferrous metals,non-ferrous metals,coations,synthetics,concretes,electric cables and optical fibers.
Abstract: On the basis of collecting more than 400 cases of histories of stress corrosion cracking(SCC) of austenitic stainless steels(ASS).an examples-base is established for the expert system of SCC diagnosis of ASS(Estar-1 system) in this work.Some empirical rules of SCC are extracted from them and the associated reasoning mode is designed in this base.It can assist the expert system in the SCC diagnosis of ASS and provide corrosive prevention measures.
Abstract: The effects of composition and structure on corrosion behavior ofNd-Fe-B alloy have been studied.The potentials of all main phase of Nd-Fe-B alloy in pure water and NaCl solution were measured.The order of potential is E(Nd-rieh)<E(Nd2Fe14B major phase)<E(B-rich).The corrosion characteristic of Nd-Fe-B permanent alloy is that the Nd-rich grain boundary phase in the alloy is easier to be corroded than the Nd2Fe14B grain phase.The experiment results of eviromented corrosion tests showed that the corrosion resistance of the Nd-Fe-B alloy in solution is improved by the addition of Dysprosium,but reduced by the addition of Aluminium to the alloy.
Abstract: The technique of aluminising on brass by powder plating method has been studied.The optimum technological conditions obtained were:temperature 600℃,time 3h and the constitute of coating agent aluminium powder 40%,NH4Cl 2% and alumina powder 58%.After aluminising,The corrosion resistance of brass increases 1.8 times,the hardness increases 25.6% and the coating thickness is 50μm.The structure of coating layer of aluminium on brass from surface to interior obtained by X-ray diffraction analysis was:Cu0.6108Al0.3892→γ2-Cu9Al4→α-CuZn(Al)→α-CuZn.
Abstract: Corrosion rates of both S-TEN3 and CRIA steels are measured in various H2SO4 solutions by the immersed method.Based upon the experiments,the important role of alloy elements in corrosion course are discussed.The results show that Sb can obviously improve the resistance property of the STEN3 steel to sulfuritc acid dew point corrosion and so can Ti to the CRIA steel.
Abstract: Corrosion rate and corrosion behavior of four cold rolled carbon steel used for radiator manufacture have been studied in different dissolved oxygen and chloric ion concentration by weight loss test and electrochemical measurement.The structure and composition of the rust layer were examined by X-ray diffraction and scanning electron microscopy.The results shown that corrosion rate is mainly dependent on oxygen concentration in heating water system,after oxygen in solution has been removed,the rust consists of magnetite Fe3O4 and chloric ion increases corrosion of material.Corrosion resistance decreases with residual/stress.
Abstract: A great number of the bits have been made in the Al-Mg alloy by electrochmical method.The distribution function of the average density of the bits and the deeppest bits is set up by the statisticao analysis.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
