A set of cyclic testing equipment simulating high-t emperature and high-velocity situations in oil refinery industry has been design ed and built up.This equipment is primarily used to study the erosion-corrosion ca used by high-temperature fluids.The oil medium in the cyclic testing equipment c an be heated up to 350℃ and the pressure limit for this system is 6.4 MPa.The h ighest flow velocity of the oil medium in the equipment can be up to 49 m/s at p resent.The flow field in the process of erosion-corrosion experiments realized b y using the testing equipment has been simulated and analyzed by the finite elem ent method.It is found that the larger the exit velocity and the diameter of the nozzle as well as the smaller the distance from the nozzle exit to the specimen surface,the stronger the fluid erosion.Adjusting the gradient of the specimen a nd the temperature of the oil medium can also change the erosion effect.On the b asis of the simulation results of the flow field,the experimental parameters for the fluid erosion have been selected by simultaneously considering the factual situations of the testing equipment.It has been proved by the erosion-corrosion experiments that property of the testing equipment is stable,the selection of th e experimental parameters is reasonable,and the equipment meets the demands of h igh-temperature erosion-corrosion experiments.

In this article,EIS by Laplace transform time domai n method was used to evaluate under-film corrosion of coated 2024T3 aluminum all oy.EXCO immersion test,optical microscope observation and statistic method were also employed. Results show that EIS by time domain method is a quick,nondestructive and quanti tative method to detect under-film corrosion of 2024T3 Al alloy.The low frequenc y impedance (Rd),high frequency capacitance (Cg) can be treated as i ndicators of under-film corrosion.Correlation was established between Rd a nd Cg and corrosion states.Statistical analysis show that log(Rd) ma tch Gumbel distribution and log(Cg) correspond to normal distribution. Investigations show that different corrosion states have different dynamic rules .If only pitting occurs on the specimen,Rd and Cg fluctuates.When th e exfoliation happens,Rd will decrease and Cg will increase with tim e.Log(Rd),which reflect the most severe corrosion in large-scale specimen, will decrease exponentially with time in EXCO solution.

A nickel-phosphor coating was prepared on the surfa ce of AZ91D magnesium alloy by electroless plating.The coating was so uniform an d dense that it had no obvious surface defects.The structure o f the coating was single phase (Ni) by X-ray diffraction and the adhesion was go od by quenching.By dynamic potential polarization,it was shown that the free cor rosion potential of the coating approached -0.4 V(SCE) and it had evident passiv ation.The coating had better corrosion resistance than the substrate,and had ext ensive application prospect.

A Fitness-For-Service software system for local cor rosion thin zone defects was developed to make safe evaluation and calculate the residual life for the equipment which contains local corrosion thin zone defect s based on the newest advantage of Fitness-For-Service technology. The software system can give the applicability automately after the data of the equipment and its defects were input. The test showed that the software can be used to make r un,repair or replace decisions to ensure that damaged pressurized equipment can continue to operate safely.

The behavior of 1Cr18Ni9Ti stainless steel surface passive film have been studied by potentiodynamic、impendance and electron probe in 0.05 mol/L H2SO4 solution containing hydrogen sulfide.The results indica ted that the thickness of passive film attenuated with the increasing content of hydrogen sulfide,but the film did not destroy at a low concentration of hydroge n sulfide,the EIS characteristic of passive film remained.The passive film destr oyed at a high concentration of hydrogen sulfide (>200×10-6),and the surf ace film turned to sulfide film,then EIS characteristic changed as a result.

The corrosion behavior of pure Cr，one low alloy st eel and an HP-type heat-resistant steel were studied in the presence of ZnCl2 and KCl-ZnCl2 deposits respectively in oxidizing gaseous environments at 450℃ .All materials suffered from seriously accelerated corrosion beneath mixture sal ts than in single ZnCl2 deposit.The oxide scales formed on pure Cr and heat-re sistant steel were easily to spall and had even worse adherence to the matrix co mpared with that on low alloy steel，whereas the latter had a higher mass gain d uri ng corrosion.Furthermore，Cr-rich Cr7C3 carbides were attacked preferentiall y induced by chlorine in comparison to the matrix of the heat resistant steel.Th e results show that the Cr-containing alloys do not exhibit excellent corrosion resistance to this chlorine-contaminant environment due to the poor adherence of the scales to the matrix.The accelerated corrosion mechanism for those Cr2O 3-forming materials is discussed thermodynamically.

In-situ infrared reflection absorption spectroscopy (IRAS) was a very powerful tool for studies of corrosion processes of the confi ned metals in the atmosphere.In this paper,an in-situ IRAS cell was set up and t he corrosion process of zinc and water evaporation in the drying process on the confined zinc surface exposure under periodic wet dry conditions was studied by in-situ IRAS.The water thickness on the confined surface of zinc could be calcul ated according to the optical index.The corrosion product formed in the initial stage of the confined zinc in the purified air with the relative humidity of 50% mainly was ZnO,The amount of corrosion product on the confined zinc surface inc reased linearly with day,the corrosion rate decreased with time during each dryi ng process.

The high temperature corrosion behavior of 310SS (s tainless steel) treated by boronizing in 2.3%SO2/S2/8.8%N2 under 105 Pa at 600℃had been investigated.Boronizing treatment resulted in formation of (Fe, Ni)2B and (Fe,Ni)B on the surface of 310SS.Corrosion of Boronizing sample s howed rapid rate in initial stages for small of Cr in outer scale.However,the bo ronizing coating had negligible effect on the corrosion resistance of 310SS.

The water uptake of two kinds of epoxy films and co atings was investigated using gravimetric method and electrochemical impedance s pectroscopy.The water barrier properties and their effect on the degradation of the interface have been studied.The results show that the water uptake of coatin g can be divided into two processes.One is the permeation of water in coating it self.The other is dispersing of water on metal surface.The bond of metal/coating interface has important influence on corrosion protection of epoxy coating.The epoxy resin,which had been blended with Morpholium Mannich base,had better corro sion resistance.

The cyclic oxidation of aluminide coatings on 16Mn s teel under the condition of quenching in water containing 3.5% NaCl has been stu died.The oxidation was carried out at 600℃ and 800℃ in air.The aluminide coati ngs remarkably improve the oxidation resistance of 16Mn steel.Increasing of the oxidation temperature or existing of NaCl in quenching water causes more severe corrosion.After cyclic test,the aluminide coatings happen to crack.However,these cracks just exist in the surface layer of the coatings.

Wire beam electrode(WBE) was applied to study the m icrobiologically influenced corrosion(MIC) of Q235 carbon steel associated with sulphate reducing bacteria(SRB) in semicontinuous culture medium(to be complete ly refreshed every 72 hours).The potential,galvanic current density and impedanc e mapping,as well as open circuit potential(OCP) and electrochemical impedance s pectrum(EIS) were measured to predict the localized corrosion under biofilm duri ng SRB growing.As a result,the OCP moved negatively gradually with time.However, The mapping showed the potential fluctuation on the WBE surface decreased over t ime due to the conductivity of FeSx(x=0.9～2) metabolized by SRB in th e biofilm.Therefore,the potential mapping could not be a criterion of localized corrosion under biofilm.Instead,the impedance mapping could give a good predicti on to the MIC.In addition,The biofilm capacity moved up to a very large level(～ 105 μF/cm2) in shape of sigmoid when SRB grew.At the same time,both solutio n resi〖JP2〗stance and charge transfer resistance decreased exponentially.〖JP 〗

NiCoCrAlY coating was deposited on a new Ni3Al-ba se alloy IC-6 using arc ion plating.The oxidation kinetic curves of alloy IC-6,N i-base alloy K17 and NiCoCrAlY coated alloy IC-6 at 900℃～1100℃ were obtained. The results indicate that exposed at 900℃,the oxide scales of alloy IC-6 consis t of α-Al2O3、NiAl2O4 and NiO.A small amount of NiMoO4 and MoO2 wer e also detected.At 1050℃ and 1100℃,lose weight occurred due to the formation o f volatile MoO3.The oxidation weight gain rate of the NiCoCrAlY coating deposi ted on alloy IC-6 o beyed the parabolic rate law at different temperatures.The coating combined with alloy IC-6 closely and no spalling and void between the coating and the interfa ce of the substrate were observed.The coating oxidation resistance remarkably im proved with α-Al2O3 scales that formed and covered on the coating at 900℃ and both α-Al2O3 and Cr2O3 scales on the coating at 1050℃.The effectiv eness of NiCoCrAlY coating was not distinctive at 1100℃ due to NiAl2O4 and NiO growing on the surface of coating.The formation of α-Al2O3 and Cr2O 3 scale is the directly reason of remarkable improvement of oxidation resistance of superalloy IC-6 covered with NiCoCrAlY coating.

This paper studied the present situation of WP alum inum alloy sacrificial anodes of sea bed oil-carrying pipelines in the oil field of south China sea.According to the results of potentiostatic test of anode,mic roanalysis of anode surface dissolution morphology,X-ray diffraction of anode co rrosion products,chemical analysis and SEM & EDS analysis,WP anode did not fit f or the long-term protection of ocean bottom oil-carrying pipelines.Moreover,it i s confirmed that the invalidity ahead of time mainly results from the structure defects.Solute segregation in crystal boundary results in intergr anular corrosion very seriously.