Three kinds of quantum chemistry methods, semiemperical SCF/PM3(improved MNDO)and ab initio SCF/STO-3G and SCF/6-31G,were applied to clarify the origin of the good inhibition performance of piperidine (PD) on passive film of stainless steel.According to the data of formation heat and absolute energy of molecules with different possible conformation,the chair style conformation of PD is stable.With O-Fe-O-Fe-O and O-Cr-O-Cr-O being succedaneums of one dimension oxide film,the optimized geometry and electron energy level of these molecules were calculated by ab initio SCF/STO-3G.On the basis of chemical reaction generalized perturbation theory,the interaction between inhibitor PD and metal oxide was discussed.The results indicated that the adsorption of PD on passive film is a charge control reaction.The adsorption of PD can be ascribed to N atom acting as electron donor to chalets with Fe and Cr atoms in oxide film. The obtained adsorpton bond energy is in agreement with the single bond energy of normal Fe, Cr complexes including nitrogen aton.Moreover,the adsorption orientation of PD on passive film was deduced preliminarily.

The electrochemical behavour of iron in carbon dioxide solution was studied using electrochemical polarization curves and AC impedance measurements.The corresponding mechanism was discuessed.Car-bon dioxide inhibited the dissolution of iron and accelerated the evolution of hydrogen.The relationship between the corrosion potential or the corrosion rate obtained by the low polarization region curve-fitting technique and the partial pressure of carbon dioxide was in accordance with the theoretical deduction.

The effect of Cl- on iron corrosion in 0.5mol/L and 0.005mol/L H2SO4 solutions containing H2S has been studied by electrochemical potentiodynamic oolarization and impedance measurements.The results show that Cl- ion can simultaneouly inhibit the anodic and cathodic reaction of iron in 0.5mol /L H2SO4 containing H2S. For the inhibition action of Cl- a critical concentration is observed and the critical point is 1mol/L. In 0.005mol/L H2SO4 containing H2S,small amount of Cl- can increase the protective property of the corrosion product on iron surface,but weaken the adhesive force of the corrosion product,however,arge amount of Cl-retard the formation of the corrosion product.

Hydrogen evolution on three sacrifical magnesium anodes AZ63,AZ41 and pure magnesium in fresh water has been studied by means of weight loss,hydrogen collection,electron probe analysis and morphological observation.The results show that all the three magnesium anodes in fresh water are in active state and the velocity of hydrogen evolution os linearly dependent on current density.Their negative differential effect coefficients in fresh water are less than that for magnesium in 0.5mol/L NaCl+Mg(OH)2(pH10.2)solution.Hence the hydrogen evoluton is not the only reason for the low current efficiency of magnesium anodes.The fall of magnesium grains may be the another important cause.

For external corrosion protection of the newly constructed φ610mm oil pipeline from Kurle to Shanshan in Xingjiang,a combination scheme of high quality coating and cathodic protetion executed partially in sacrificial anode mode was designed.Due to the high resistivity of soil in this region,extruded magnesium ribbons instead of traditional cast ingots were selected as sacrificial anodes.Conventionally,the continuous ribbon anodes were installed lengthwise in a trench parallel to and of the same length as the pipeline to be protected.In this prohect,however,only a short section of ribbon anode was found sufficiet to provide a high level of protection for a considerabl longer pipeline.Such a special configuration was preliminarily verified on a φ377mm pipeline in Shandong and then put into practice in Xingjiang.Two groups of anodes consisting of 2×250m or 4×125m ribbons were installed respectively at two test stations separated about 1Km.Potential measurements indicated that successful protection was achieved along the pipeline longer than 80Km

Maximum corrosion depth measurement can evaluate corrosion damage of aluminum alloy precisely.Unfortunately,this kind of method is destructive.To find a non-destructuve and in situ method which can be used as practical and accelerated corrosion test,an electrochemical method-free corrosion potential measurement was developed.EXCO test was carried out according to HB 5455 standard.Free corrosion potential and maximum corrosion depth of LY12CZ aluminum alloy were measured.The kinetics law of the aluminum alloy corroded in EXCO solution can be divided into two segments.In the earlier stage its corrosion rate is faster while in the later stage it becomes slower and keeps constant.Free corrosion potential of the alloy increases with immersion time at first,and then decreases exponentially.The relationships between free corrosion potential and maximum corrosion depth of the aluminum alloy was established.Where D is the maximum xorrosion depth,E is the free corrosion potential and t is immersion time.Thus by measuring the free corrosion potential of LY12CZ aluminum alloy,the maximum corrosion depth can be evaluated and its corrosion damage can be predicted.

The state of the art and development of electrochemical corrosion study are reviewed from the mechanism and experimental point of view.The electrochemical corrosion behavior of metals could be studied in microscope in situ.According to the electrode reaction properties,the relationship between the corrosion behavior and characters of electrode interface was disccussed.Metals with different electrode interface exhibited defferent corrosion behavior.The main study methods for the properties of corrosion interface included electrochemical methods,in-situ spectroelectrochemical and scanning probe techniques.The latest results of the study on corrosion interface were presented.

The corrosion behavior of zinc in ammonium chloride solution with thiosemicarbazido(TSC) was studied by means of corrosion potential measurement,electrochemical impedence spectroscopy and weightloss method.The experimental results showed that TSC had remarkable inhibition effect on the corrosion of zinc in 26% ammonium chloride solution.The inhibition efficiency of the TSC increased with the increase in its concentration up to 0.2g·L-1.The inhibition of TSC for zinc was found to be the geometric blocking effect,and its adsorption isstherm approximately followed Langmuir isotherm equation.

The cementation of Zr, activated and catalyzed by rare earth elements,on 45 steel surface under gas-phase condition was investigated.Chemical composition of the cemented coating was analyzed by SEM-EDS、XPS and XRD.Meanwhile,weanwhile,weight loss test,humid thermal and neutral salt-fog method were applied to investigate the effect of cementation of Zr on corrosion resistance of 45 steel.The results showed that the cementation of Zr with the assistance of RE greatly improved the corrosion resistance of the steel surface.

By weight loss and electrochemical measurements and XPS analysis,the inhibition effect of NaNO3 for 316L stainless steel in Cl- containing itaconic acid media was investigated.The results showed that the pitting corrosion of the steel in the media could be prevented effectively in the presence of some amounts of NaNO3,which could raise the critical pitting potential up to the transpassive potential so as to result in a superior pitting resistance.The competitive adsorption between NO3- and Cl- on the steels surface might be a main mechanism for inhibition.In view of the dual functions of NaNO3 as an inhibitor and as a nitrogenous source necessary for the fermentation process,it is feasible for NaNO3 to be recommended for use in the production of itaconic acid by fermentation

The effects of aging temperature on microstructure,mechanical properties and stress corrosion resistance in H2S medium of Fv520(B) steel (0.05C,14.5Cr,5.5Ni,1.8Cu,1.70Mo,0.35Nb)have been studied by X-ray deffraction,TEM and SEM.The results show that the strength decreases with the increasing aging temperature in the rang of 470-620℃.The amount of austenite and the stress corrosion resistance increases with the increasing aging temperature,and reaches the highest level at 620℃.Aging phases begin to precipitate at 470℃,and grow with the increase of the aging temperature.The stress corrosion resistance is related to the shape of aging phases,tempering level of martensite and the amount of remaining austenite.The best mechanical properties and stress corrosion resistance can be obtained by aging at 560℃.

By using potassium dichromate as oxidizer and sodium bisulfite as reductor,the surface of rapidly chilled NdFeb mini-crystal magnetic powder was treated under the strong oxidation condition.The hot oxidation mechanism of the treated magnetic powders was studied.The results of weight gain during dry and wet oxidation tests indicated that the above-mentioned preoxidation and preoxidation-reduction treatment can considerably inprove the oxidation resistance of the magnetic powder.For example,the weight gains reached 0.024% and 0.077% after oxidation at 430℃ and 500℃ for 1 hr,respectively,for the treated powder,while 2.3% and 3.83% for the untreated powder.During the wet oxidation test (80℃,RH90%,100hr),the corresponding data were 0.067% and 7.30%.The treatments increased B,H,(BH)max of the experimental cohesional magnet by 60%-100%.XPS of the magnetic powder before and after the treatment were compared and the results showed that Nd,Fe on the surface of untreated powder were in oxidized states and the surface of the treated power was covered by chromium oxide.The presence of the latter had the action of antioxidation and therefore enhanced the magnetic capability of the cohesional magnet.