Annealed pure specimens were pre-charged with hydrogen at virous current densities.Effect of hydrogen on anodic polarization and passivation process of nickel was investigated using electrochemical method and theoretical analysis.The results showed that precharged hydrogen shifted the self-corrosion potential negative,diminisked passived potential region,in Na2B4O7 solution.After charged with hydrogen and then passisived film in NaCl solution decreased with the increase in hydrogen content.

Electrochemical impedance spectrum(EIS)was wmployed to study the corrosion of FeAl in molten (Li,K)2CO3 at 650℃.It is shown that the EIS exhibited the characteristics of diffusion-controlled reaction at the initial corrosion stage,while it was composed od two capacitance loops during wxtended corrosion.The corrosion of FeAl at the initial stage was controlled by the diffusion of oxidants O2 and O22- formed by the chemical dissolution of oxygen in the melt.The concentration of O2- at the scale/melt interface generated by the reduction of O2- and O22- tended to increase,which might promote the reaction of Fe2O3 grown on FeAl with Li2O, forming LiFeO2. The formation of LiFeO2 gave rise to a larger amss gain of FeAl,but provided a better protection to the alloy.With the formation of continuous external LiFeO2 and inner Al2O3 layer,the corrosion of FeAl was controlled by the transfer of the charged particles through the scale.Corresponding equivalent circuits were also proposed to fit the EIS of FeAl.

The Ni-P electroless coatings with different P contents were prepared by varying the compositions of electroless plating bath,and the P contents were determined using X-ray energy disperse spectrum.The effect of Ni-P coating on SCC of 304L stel welding joint in boiling 42% MgCl2 solution and in 5% HCl solution at 25℃ was investigated by means of slow strain rate tensile test and constant load tensile test.Results showed that a perfect Ni-P electroless coating could effectively prevent substrate material from SCC at low stress.Under higher stress（σ＞σs） or in the presence of defects or cracks in the coating,SCC originated from defects or cracks in the base material under the coating.The coating did not provide electrochemical protection to the substrate bacause of the relative relationship of corrosion potentials for the coating and the substrate.

The oxidation kinetics of Co-based superalloy DZ40M in air at 900-1100℃ has been determined,and the oxide compositions at different exposure temperatures for various times have been examined by XRD.The kinetics indicated that this alloy followed the parabolic law at 900 and 1000℃ during isothermal oxidation,and followed the nearly linear law at 1050 and 1100℃ due to serious cracking and spalling-off of the oxide scales.The kinetic behavior of the alloy at all exposure tempweatures was affected greatly by the configuration of Cr2O3 in outer oxide scale.The formation mechanism of oxide scale at 900and 1000℃ deffered from that at 1050 and 1100℃,with the former having a continuous Cr2O3 layer.

Plasma Ni-Cr surface alloying was applied on mild steel by double Glow Plasma Surface Alloying Process.The sputtering and absorption of alloy elements,two basic processes that determined the kinetics of the alloying process,were investigated on the basis of discharge and sputtering theories and the experiment results.The study indicated that the alloying process was effected remarkably by the discharge parameters.The sputtering efficiency of the sputtering target was determined by the voltage applied on it and also the discharge pressure.High voltage and low discharge pressure and substrate bias should be chosen moderately to obtain the highest efficiency of the alloying process,the optimums being 40Pa and 400V respectively.Besides,the distance between sputtering target and substrate also affected the absorption ratio.Reduving distance was beneficial to the absorption process especially when it was at 20mm or shorter.The close correlation between the distance and the absorption ratio might result in the non-uniformity of the alloyed layer since it was inevitable that there would be some difference in the distance in practical operations.so the selection of distance should be considered in association with the specific processing condition.With certain sputtering supply of alloy elements,the larger the ratio of the absorption,the higher the quality of the alloyed layer.The absorption ratio should be the main concem with respect to the optimization of the rocessing coditions.

Corrosion of Co-15wt% Y alloy was studied in H2-H2S-CO2 mixtures with 10 -19Pa O2 at 600℃ or 10 -15Pa O2 at 700℃ and with 10 -3 Pa of sulfur pressure.The corrosion rates of the alloy were compared with those of pure cobalt and yttrium.The addition of yttrium to cobalt was only slightly beneficial.For yttrium content of 15wt%,the corrosion rate was reduced only to a limited extent at 600℃,and even slighly increased at 700℃ with respect to pure cobalt.The alloy formed extermal scales of cobalt sulfide containing yttrium sulfide-oxide particles in its inner part.Beneath the external scales,a region of internal sulfidation-oxidation of yttrium was also present.Thus,cobalt cold diffuse through intermediate regiion to form the outer cobalt sulfide layer at significant rates.The yttrium content in this alloy was still insufficient to form cobalt-free external scales.These results were interpretted by taking account of the limited solubility of yttrium in cobalt and the presence of intermetallic Co-Y compound in the alloy.

A thermodynamic analysis on the characteristics of iron/naphthenic acid/hydrogen sulfide ocrrosion system is presented.The results indicate that the corrosion products of this system are dependent on the partial pressures of hydrogen sulfide and naphthenic acid.In the passivation region,the diffusion process of sulfide in the surficial layer is the rate-determining step of corrosion.In the corrosion region,however,the corrosion rate is controlled by the reaction process of naphthenic acid on iron surface.And corrosion of iron can only occur when the partial pressure exceeds a critical value.On the basis of the phase diagrams,the reasons for the appearance of two peaks of corrosion rate with the change of temperature are discussed.It could be attributed to the formation and the decomposition of active sulfides.

The inhibition of 2-Mercaptobenzoxazole (MBO) against copper corrosion in 3% NaCl solution was investigated by means of potentiodynamic polarization measurements.MBO hindered both the anodic and cathosic reactions,especially reduced enormously anodic corrosion current in relative broad potential range.Its inhibition efficiency was dependent on MBO concentration,the corrosivity of the medium in which the inhibitive film formed and the duration when copper samples were immersed in the medium containing MBO.The inhibitive film formed in the MBO solution containing sodium chloride possessed much higher inhibitive film formed in the MBO solution containing sodium chloride possessed much higher inhibition capacity than that formed in plain MBO solution.An inhibition efficiency of about 99% could be obtained by immersing Cu sample in 3% NaCl + 1mmol/L MBO for above 20h. With the formation of the inhibitive film on copper surface,mass gain could be measured by quartz crystal microbalance (QCM).It is concluded that the inhibition of MBO is related to the corrosion of copper.

The protection film formed on copper in 1mmol/L MBO solution containing NaCl,was characterized and studied by means of AES,XPS,FTIR and in situ STM.The FTIR characteristics for the surface of copper sample immersed in the solution for various durations were different from that for MBO.XPS data indicated that the chemical circumstance of S and N atoms in the MBO inhibition film formed in MBO + NaCl solution changed evidently in compact three-dimension film on copper surface in MBO solution containing NaCl.It is concluded that MBO reacted with the cuprous species from copper corrosion,and produced a water-insoluble material to form the inhibition film.

The geometric configuration of furan and its derivatives upon adsorption were optimized using AMI method.Linear regression showed good correlation between the inhibition efficiencies and the front orbital energies,and the net charge of the oxygen atom in the furan ring,respectively,An model of Al cluster surface consisting of 10 atons on (111) crystal face of aluminium was proposed for further study.The system including inhibitor and Al-cluster surface was calculated.The calculation showed that the inhibition effciencies increased with the increase in stabilization energies,and with the decrease in adsorption length.The inhibition mechanism and the adsorption modes were discussed.As and example, the inhibition efficiency of furan-2-alcohol was predicted according according to the calculated results,and was verified experimentally.