The Ni/n-SiO2 coating was deposited by pulse-reverse brush plating.The surface morphology of the coating was analyzed by SEM,the porosity of the coating was evaluated and the corrosion resistance of the coating was measured in the solution of sea water.The corrosion mechanism of the coating was also discussed.The result shows that,compared with Ni and Ni/n-SiO2 coatings deposited by direct current,the Ni/n-SiO2 coating by pulse-reverse current has much compact and finer surface morphology,lower porosity and better corrosion resistance.

Ni-based alloy coatings were made by spray welding on surface of the mild steel(1Cr18Ni9Ti).The microstructure and performance of the coatings were investigated by optical microscope，X-ray diffraction，Vickers hardness，scanning electron microscope(SEM) and vibratory cavitation apparatus.The results show that the Ni60 coating has much higher hardness and finer structure than Ni25 coating and 1Cr18Ni9Ti.In addition,the vibratory cavitation result s show that the mass loss increases with increasing test time.These results indicate that the cavitation erosion resistance of Ni60 coating is much better than that of the Ni25 coating,due to higher hardness and finer structure.Furthermore,the cavitation erosion mechanisms were studied also in the end of this paper.The results showed that higher hardness and finer structure can increase the vibratory cavitation resistance of coatings.

Potentiodynamic polarization measurement was used to study effects of temperature,Cl- concentration and pH on the electrochemical behavior of NiTi shape memory alloy (SMA)in the synthetic saliva according to the orthogonal testing method.The results showed that temperature,Cl- concentration and pH had great influence on the pitting behavior of NiTi.The breakdown potential was most negative at 25 ℃,and it increased with the increase of temperature.The breakdown potential kept in high level when the Cl- concentration was not more than 0.1 mol/L,while it dropped sharply with the continuous increase of Cl- concentration. The breakdown potential was highest at the solution of pH 6.0.

he formation of the electrolyte droplet due to the deliquescence of soluble salt particles is one of the cause for the acceleration of atmospheric corrosion.A lot of micro-droplets,1 μm～10 μm in diameter,were observed around the edge of the main-droplet formed by the deliquescence of salt particles deposited on metal surface in atmosphere.In this paper,the characteristics of the formation and spreading of the micro-droplets were investigated in detail in a humidity-controlled chamber.The results showed that oxygen,relative humidity and a combination of salt particles and metals played important role in the formation of micro-droplets.Two premises were necessary for the formation of micro-droplets in atmosphere.First,the relative humidity should exceed the saturated relative humidity of the main-droplet.Another was that the metal substrate could be eroded under the main-droplet.

The buried tests and the electro-chemical experiments were applied to investigate the corrosion sensitivity of X60 steel in typical soil environments of Shan-Jing gas pipeline.There is quite different on the soil corrosion sensitivity along the gas pipeline due to the difference of the soils.The one of three typical test soils has higher corrosion sensitivity.The morphology of the soil corrosion is characteristic of pitting and ulcer corrosion .The results of statistical analysis show that the logarithm of the maximum depth of the pitting is submitted to the normal distribution.The self corrosion potentials and the polarization curves depend on the content of water in the soil intensively.The process of the electro-chemical corrosion is mainly controlled by the electro-chemical polarization.

To investigate the influence of micro-arc oxidation (MAO) treatment,a layer of ceramic coating was prepared on AZ91D magnesium alloy by using MAO technique in alkali-silicate solution.The corrosion resistance of MAO treated and untreated AZ91D magnesium alloy was studied in 3.5mass% NaCl solution by means of the electrochemical impedance spectroscopy (EIS) method.During the immersion process,both specimens exhibited two kinds of impedance diagrams,two capacitive loops at the initial stage and one capacitive with one inductive loop at the later stage.Compared with the untreated magnesium alloy,the MAO treated specimen exhibited positive corrosion potential and increased resistance.Both the corrosion potential and the resistance of the MAO treated specimen fluctuated at the initial stage of immersion,afterwards decreased.A two-stage deterioration mechanism,the MAO coating deterioration and the Mg alloy localized corrosion,was proposed to describe the corrosion process of the MAO treated Mg alloy. 

It is an effective method to improve the corrosion resistance of magnesium alloys by using electroless nickel planting. However, the pretreatment of substrate can influence the adhesion of the coating on magnesium alloys significantly due to their high chemical activity. The influences of different pretreatment techniques on the adhesion of electroless nickel planting on magnesium alloy have been studied in this paper. Furthermore, the adhesive force between the coating and the magnesium substrate has been estimated by used bend test, file test, and scribe test. Through the test, we come to the conclusion that by using the one step pretreatment and once zincification, the film of the sample has the best adhesion; at the same time, the surface morphology has proved that the mesosphere is the thinnest.

TiN multi-permeated layers were formed on the steel surface with diffusion layer and deposition layer by means of both double glow-discharge surface alloying process and reactive sputtering.The surface appearances and composition and its corrosion-resistance in 10% H2SO4 and 3.5% NaCl of TiN multi-permeated layers by using different processes were investigated.The results indicated that the TiN multi-permeated layer was uniform and compact,th e content of atom Ti,N gradually decreased with increasing distance from the surface.The adhesion of the TiN coating was very strong,its thickness was more than 10 μm.The corrosion resistance of the TiN multi-permeated layer in 10% H2SO4 and 3.5% NaCl was excellent,the corrosion rate was only 0.156 g/(m2·h) and 0.025 g/(m2·),respectively.

High strength Al-Zn-Mg-Cu aluminum alloys are widely used in airframe construction.However,this series of alloys are susceptible to stress corrosion cracking (SCC) to limit their usefulness.The tempered conditions and microstructural characteristics of Al-Zn-Mg-Cu aluminum alloys are well known to have a strong effect on SCC susceptibility.7B04 aluminum alloy belongs to Al-Zn-Mg-Cu alloys and is gained from 7A04 alloy through purification.The purpose of this investigation is to evaluate the influence of tempered conditions upon the SCC susceptibility of 7B04 alloy.The SCC behavior of 7B04 plate material was investigated in short transverse direction performing constant load test usi ng uniaxially smooth tension specimens,constant strain loaded tests using C-ring specimens and pre-cracking tests using double cantilever beam (DCB) specimens.The study also included the fractography examination by scanning electron micrograph (SEM).The results show that the resistance of SCC is much related to the tempered conditions.The SCC susceptibility of 7B04 alloy decreases from the near peak strength of T6 temper to over-aging T74 then to T73 condition.The threshold values of stress corrosion cracking (σth ) of T6 temper and T74 temperare 120 MPa and 300 MPa respectively.The threshold stress intensity factor for susceptibility to stress corrosion cracking (KISCC) of T74 temper is two times of T6 temper and the stage Ⅱ crack growth rate (da/dt)Ⅱ of T74 temper is also much lower than that of T651 temper.The fractographs of T6 temper and T74 temper reveal intergranular fracture.While the fractographs of T73 temper do not show intergranular fracture,but pitting corrosion characteristic and the KISCC is almost the same as KIC.This indicates that there is hardly SCC susceptibility for T73 temper.That is related to the microstructure difference when the temper is different.The main precipitated phases in the T6 temper are composed of G.P zone and small quantity of η′ phase,there is not the obvious precipitated free zone(PFZ),while in the T74 temper there are η′ and η phases and their sizes are getting bigger, and the precipitate free zone (PFZ) gets wider.The increasing of precipitate size and PFZ can generally improve the SCC resistance.

By means of the constant current gathering volumes of hydrogen evolution,potentiodynamic and the surface corrosion morphology observed,the effect factors of the hydrogen evolution on Al anodes in strong alkaline solution were studied.The factors includes the alloying elements,the concentration of KOH solution,the temperature and the anti-hydrogen evolution agents.The aluminum alloy anode which contains mixed rare earth elements(RE) had the lower se lf-corrosion property and the hydrogen evolution rate in its surface also decreased greatly.When the concentration of KOH solution was 4 mol/L,the anode had the better activity and the lowest H2-evolution rate,The higher the temperature,the faster the H2-evolution rate.The anti-hydrogen evolution agents (eg.aminophenol) could reduce the H2-evolution rate.The results showed that the mixed rare earth(RE) aluminum alloy,4 mol/L KOH solution and the 0.4 mol/L o-aminophenol additive were suitable conditions to reduce the hydrogen evolution rate on the surface of A l-anodes,especially at the high temperature.

The dissolution and deposition of stainless steel electrode under non-symmetrical square wave electric field were investigated by using atomic absorption spectroscopy (AAS) and electrochemical measurement.The effects of the parameters of alternating electric field on the growth of passive film and the dissolution of alloying element in stainless steel were studied by analysis of the composition of passive film and the bath solution.Result shows that the parameters of alternating electric field have marked effect on the electrochemical behavior of stainless steel,and the role of alloying element in stainless steel is different in the dissolution and deposition process.

Comparative studies on the failure behaviour of the liquefied petroleum gas(LPG) spherical tanks,which were manufactured from 16MnR steel and SPV50Q steel respectively and working under the wet H2S environment,were conducted.By observing the crack feature of the samples cut from the severely corroded shell plates removed from the integral 16MnR spherical tank and the crack morphologies of the metallurgical replica photos made on the internal surface of SPV50Q tank on site,as well as analysing the hardness and welding residual stress measured on site,it was found that the failure of 16MnR tank was attributed to hydrogen-induced cracking(HIC) and the damages occurred on the base metal.While for SPV50Q tank,the failure was attributed to sulfide stress corrosion cracking(SSCC) and cracks mainly appeared in the heat-affected zone(HAZ) around the welded joints.

This paper summarizes the benefits of application of microencapsulants to oilfield corrosion inhibitors，the principles of controlled release and microencapsulation technologies in which spying drying,interfacial polymerization emulsion polymerization,orifice-(bath-fed)are described mainly.Finally a review of evaluation about performance of microcapsule product and the prospects of application of microencapsulants to oilfield corrosion inhibitors are presented.