The corrosion behaviors of 45# carbon steel,1Cr18Ni9Ti,304 stainless steel,and Ni-P alloy coatings in sulfur-bearing solution were studied by potentiostatic polarization method and gravimetric method.The results showed that at lower temperatures,the effect of sulfur concentration on cathode polarization and anodic polarization of four kinds of materials is weak.The polarization curves of 1Cr18Ni9Ti and 304 stainless steel are similar,their polarizations both are typical electrochemical corrosion course,and their self-corrosion potential and self-corrosion current are similar too.Passivation appears in Ni-P alloy coatings,and diffusion controlled by anode appears in 45# carbon steel.As the temperature increases,the corrosion rate increases,and the polarization rates of 1Cr18Ni9Ti and 304 stainless steel rise,whereas the passivation of Ni-P alloy coatings weakens.1Cr18Ni9Ti,304 stainless steel and Ni-P alloy coatings are corrosion resistance materials in sulfur-bearing solution.

The morphology of sulfate- reducing bacteria (SRB),microbial biofilms，corrosion product film and corroded A3 steel have been observed by atomic force microscopy (AFM).The results of high-resolution topographical images gave the information of the size of the cell， the thickness of biofilms and corrosion product film and the pitting corrosion depth. It can be concluded that compact sulphide films were formed on the surface of A3 steel and then microbiologically attached and formed biofilms during the process of microbiologically influenced corrosion.The corrosion of A3 steel mainly presents pitting corrosion character.

Electrochemical impedance spectroscopy (EIS) measurements were performed on sensitized and solutioned 304 stainless steels respectively in the process of Electrochemical potentiodynamic reactivation (EPR) polarization in 0.5mol/L H2SO4+0.01mol/L KSCN solution.The variation rules of impedance resistance in process of EPR polarization were analyzed.It was found that the EIS spectra of the stainless steels during EPR polarization exhibited features of active dissolution,activation-passivation,passivation and reactivation.Before reactivation,the two kinds of stainless steels had the same EIS characteristics.In the reactivating region the passivated film dissolved partially and the impedance modulus of the sensitized stainless steel was one magnitude order smaller than that of the solution-treated stainless steel,indicating that intergranular corrosion had occurred on the surface of the sensitized stainless steel.In addition two capacitive loops appeared in the EIS of the sensitized stainless steel and it was quite interesting that the second arc at the low frequency range was actually a negative resistance capacitive loop.These results may provide essential basis for detecting intergranular corrosion susceptibility of stainless steel by electrochemical impedance spectroscopy.

Nanocrystallized bulk 304 stainless steel(304ss) was prepared by the severe rolling equipment. X-ray diffraction (XRD),optical micrograph and transmission electron microscopy (TEM) were used to characterize micro-structure of materials. Meanwhile,using different electrochemical methods,such as polarization curves,electrochemical impedance spectrum (EIS),and Mott-Schottky analysis,the effect of chloride ion attack on the passive film was investigated in 0.05 mol/L H2SO4+0.05 mol/L NaCl aqueous solution. The passive film formed on surface of nanocrystallized bulk 304ss was more compact and more protective to chloride ion than that formed on its counterpart alloy. Meanwhile,the donor carrier density decreased in the passive film,which restrains the passive film electrochemical reaction and improves the passive film stability. Therefore,the nanocrystallized bulk 304ss was more protective against chloride ion attacking in 0.05 mol/L H2SO4+0.05 mol/L NaCl aqueous solution.

The corrosion behaviors of 304 stainless steel (304SS) in 3%NaCl solution and in mixed solution of 20 g/L NaCl+0.67g/L (NH4)2SO4+2.3 g/L NH4Cl were investigated using polarisation curve and electrochemical impedance spectroscopy (EIS) methods.304SS maintained its good passive state after immersed in the mixed solution for 750 h.Its average corrosion current density in this medium was determined to be of 0.056 mA/cm2.It was found from EIS studies that in 3%NaCl solution,304SS exhibited a pitting corrosion behavior of bare metal with a thin passive film;while in the mixed solution,it showed a more typical feature of stable and complete passive film.The ohmic resistance of this passive film was much smaller than the charge transfer resistance of corrosion reaction.The good anti-corrosion performance of 304SS could be mainly attributed to the inactivation of surface site rather than to the barrier effect of the passive film against the ionic conductance or against the diffusion of reactants /products.

Simulated Al2Zn segregation alloys were developed according to the average elements distribution of zinc enriched zones of Al-Zn-In alloy. Open circuit potential against time,polarization curves,and electrochemical impedance spectroscopy were employed to study the electrochemical behavior of Al-Zn-In and simulated Al2Zn alloys. The results showed that the simulated Al2Zn alloy exhibits a more electronegative open circuit potential and a lower self-corrosion rate as compared with those of Al-Zn-In alloy. However,the Al2Zn segregation in Al-Zn-In alloy can be attributed to the formation of micro-local galvanic corrosion that leads to the preferential dissolution of Al2Zn and the loss of current efficiency.

Carbon/epoxy composites were studied in this paper.In order to find the most important factors which could destroy the performance of the composite materials,corrosion tests were carried out by means of immersion.The test conditions were decided by the orthogonal tests of three factors i.e.temperature,concentration and the test period.The results showed that the immersion deteriorated the properties of composites,as well as that the solution temperature was the most important factor among the three factors.

The stress corrosion behavior of 304 stainless steel in the solution saturated by H2S and the standard solution of NACE was studied with electrochemical test and slow strain rate tension (SSRT) test.The results indicated that being the Cl anion in the solution saturated by H2S,the corrosion potential and pitting potential of 304 stainless steel had significantly decreased.The pitting tendency had increased and the resistance to sulfide hydrogen stress corrosion had decreased.

Healing of hydrogen-attacked (HA) cracks in carbon steel was studied by using hot press treatment.Under hot plastic deforming at 1000°C and the deformation rate of 40%,the most of HA cracks can be recovered completely within 15 min.Partial HA cracks,which has not been recovered by hot-press treatment,present the spherical cap-shaped with the length of about 4 μm～8 μm.Comparing with the results of high temperature treatment without press (cyclic heat treatment between room temperature and 1000 ℃ for 10 h),both the healing degree and speed under hot plastic deforming are improved obviously.There are not distinct difference of healing results between the direct hot-press healing and pre-heated treatment before hot-press healing.That means the decomposition of methane in HA cracks is not the key step during the whole healing process.

The relativity between image feature and pit distribution characteristic of corroded surface is studied.According to measure data of carbon steel samples corroded in soil，it can be sure that the distributions of corrosion pit diameter and depth obey exponential function equation in certain region.In other words，there exists a good linear section between corrosion pit diameter or depth and corresponding appearance probability in a double logarithmic coordinate system,which linear slope is fractal dimension (FD) for pit diameter or depth distribution denoting the roughness of corroded surface.Simultaneously a new approach is proposed based on box-counting method to estimate the fractal dimensions,D2d and D3d of corrosion images.Use a great number test data to prove a good linear relation between image D2d and D3d respectively with FD for pit diameter distribution and pit depth distribution.They are approximating equality in value.This result provides a simple and rapid method to research the rule of pit distribution on real corroded surface according to corrosion image feature.

The mathematical model of cathodic protection optimization for corrosion engineering and its numerical method was considered. In order to optimize the design of anode ,a new inverse problem of partial differential equation was presented.The numerical results of 2D/3D I-type and X-type node in nonlinear dynamics system were got respectively,and also were compared with the experimental results.The optimization model and numerical method was reasonable and effective.

The samples of the reinforced steel in acidic environment were taken separately above 10 years in usage.The rebar was analyzed by the energy dispersive spectrometry（EDS），X-ray diffraction( XRD),scanning electron microscope(SEM) and the mechanical method to investigate the corrosion behavior of the rebar,the chemical compositions and the microstructure of the cement and the mechanical performance individually.Furthermore the instantaneous state sampling method was taken to estimate the contents of the main corrosive gases in the environment quantitatively.The results have shown that the adsorption and deposition of the sulfur element on the rebar made much contribution to the corrosion of the reinforced steel.The corrosion behavior in the acidic environment is different from that induced by the chloride ion .The gases which contain the sulfur element can react with the main compositions of the cement and therefore made the microstructure of the concrete changed ,which play an important role in the neutralization of the concrete.

This paper introduced the mechanisms of intergranular corrosion（IGC）of 18-8 austenitic stainless steel.Some process factors affecting the IGC are discussed as wel1,in which carbon,chromium and nitrogen etc in alloys and hot working,casting,welding etc were considered.The IGC prevention methods of 18-8 austenitic stainless steel are discussed.