A series imidazoline derivatives, which have differ en t molecular structure and function group, were synthesized and investigated resp ectively for the inhibition characteristics, the effect of temperature on the in hibition efficiency by potentiodynamic polarization curve and electrochemical im pedance spectroscopy (EIS) in H2S solutions. The results show that imidazoline derivatives have a good inhibition to the mild steel in H2S solutions, that i s strongly dependent on the chemical interaction between imidazoline molecule and the surface of metals. When the number of carbon atom in hydrophobic side chain is less than 13 and there are some function groups (such as double-bond; hydroxy l) in hydrophobic side chain, the employed imidazoline compounds present anodic inhibitor's performance, whereas the compounds present cathodic type inhibitor' s performance when the number of carbon atom in hydrophobic side chain is more t han 13. The length of side chains (including hydrophobic and hydrophilic chain) and the different function groups (such as double-bond; hydroxyl) in imidazoline ring play an important role in the inhibition performance and mechanism.

This paper studies the effects on corrosion resista nce of GCr15 steel surface and its microstructure using the multiple treatment o f RE permeation combined with laser melting solidification.The results show that the corrosion resistance of samples with multiple treatment has been improved s ignificantly,in comparison with those treated only by RE permeation.Under acid e nvironment,both polarization current density and passivation current density rem ain low and polarization potential moves to negative-going direction,resulting i n a broader passivation zone; in addition,the enclosed area in cyclic voltammete r curves is decreased obviously with a sharp reduction of corrosion current dens ity.SEM and XRD are applied for analyzing the improvement mechanism of corrosion resistance.

The cyclic oxidation behavior of IN738 alloy and it s nanocrystalline coating has been studied. The results indicated that the cycli c oxidation resistance of nanocrystalline coating was better than that of IN738 alloy at 950℃.The oxidation of nanocrystalline coating formed a double externa l oxide scale without internal oxide or nitride. The scale consisted of an outer part of Cr2O3 and spinel and an inner part of a continuous Al2O3 scale, which offered good adhesive and protectiveness. Thus,the cyclic oxidation resi stance of the coated IN738 alloy was significantly improved. 

Changes of the surface state during the pretreatmen t of electroless nickel plating (EN) on magnesium alloys were studied using weig ht loss method,scanning electron microscopy (SEM) and X-ray photoelectron spectr oscopy (XPS).The results showed that the pretreatment of electroless nickel plat ing on magnesium alloys was a process of one protective film replacing another a nd magnesium was protected all the time.Due to the formation of Mg(OH)2 and Mg F2 film on the surface,alkaline cleaning and activating made little attack to the substrate.Different etching solutions gave different etch rates and resultan t morphologies.The CrOOH- containing film,which was formed during etching,disapp eared after activation.Effects of the changes of surface state during the pretre atment on subsequent EN procedure were also discussed.

In this paper，the biofilm of sulfate-reducing bact eria (SRB) which plays an important role in corrosion of 70/30 Cu-Zn alloy under anaerobic condition has been studied.The API medium was used to culture the SR B in Zhongyuan oilfield.Potential/time measurement showed that the presence of SRB makes the corrosion protential more active with SRB growth metabolite.Elect rochemical impedance spectroscopy (EIS) was used to analyse the electrode proces s of 70/30 Cu-Zn alloy with SRB biofilm.X-ray diffraction and EPMA were used to analyse the corrosion products.The results show that the variation of activity of the SRB biofilm with SRB growth can be found from the EIS in inoculated medi a.The crystal of sub-copper sulfide (Cu2S) exists in the SRB biofilm.

Scanner is used to acquire corrosion images of carb on steel and low-alloy steel in seawater and in order to show the corrosion moda lity clearly the images are pre-processed by the average value filter and non-li near fuzzy enhancement methods. The gray relational analysis and canonical corre lation analysis are used to analyze the relations between grey data and corrosio n data of metallic samples. The results show that there is higher gray rel ational grade. The canonical correlation coefficient between grey data and uniform corrosion lo st-weight is 0.99 while the coefficient between grey data and localized corrosio n depth is 0.98. Using artificial neural network theory, the model between the g rey distribution of metallic samples and localized corrosion depth has been deve loped. According to this model, there are only 3.89 percent absolute error betwe en the predicted result and the real value and the error will decrease if normal samples increase. With a high correlative coefficient, 0.98, the linear relatio n al model between the grey distribution of metallic samples and uniform corrosion lost-weight has been studied, too.

The characteristics of current fluctuations on carb on steel in phosphate+borate buffer solutions containing chloride were studied u sing electrochemical methods.Current fluctuations were recorded at pitting poten tial Eb or above Eb during both potentiostatic and potentiodynamic polarization. Although the background current did not show continuous increase,pits were obser ved after the test,which may be the result of repeated metastable dissolution ar ound the active sites on the surface.At constant potential,the fluctuation frequ ency decreased with time,and the peak currents follow normal distribution.Increa sed potential led to higher peak currents,but exerted no influence on the fluctu ation frequency.All the current peaks have the type of quick increase and slow decay in exponential forms.The mechanism of pitting of mild steel in the system was discussed.

Although cathodic protection has been widely applied to oil well casings,it is a challenging job to determine the cathodic protecti on level of well casings at any depth without interruption of production. In thi s paper,a new method was established to calculate the potential distribution of well casing cathodic protection with several wellhead electrical measurements(i ncluding the applied current,the cathodic protection potential and the native-s tate potential) and well completion data(such as lengths and unit length resista nces of outer and inner casing). When the method was applied to Well A in Texas, the excellent agreement was obtained between measured and calculated cathodic p rotection potentials,the maximum percent difference was less than 2%.

Artificial neural networks are forms of artificial intelligence that learn correlative patterns between input and output informatio n without a specific model. Then they use the learned relationships to make pred ictions. Five back-propagation artificial neural networks were constructed to re cognize certain relationships in hydrogen attack to predict the time to incubate fissuring of 0.5Mo and carbon steel. Given the two parameters, environmental te mperature and hydrogen pressure, these neural network models can offer a predict ion with certain accuracy. The feasibility of the model was verified by the data from papers. It is proved that the ANN technology is applicable to the evaluati on of the complicated system of hydrogen attack, and also gives a base to develo p the expert system and residual life evaluation system for hydrogen attack.

The fundamental on grey target is introduced,and th e target pattern of grey situation decision is used to evaluate and to classify the comprehensive corrosion and protection status of the underground petroleum p ipeline.The result indicates that the pipeline can be protected perfectly as gre y grade ≤2,and the pipeline runs the risk of corrosion invalidation as the grad e ≥4.Four factorial weights acting corrosion and protection status of the pipe line are separately coating resistance 60.87%,cathodic protected potential 18.84 %,corrosion current density 11.59%,pipe-earth potential 8.70%.The grey target me thod is useful for the preventive repair on pipelines.