A computation approach using wavelet transformation and artificial neural network (ANN) to analyze and quantify the atmospheric corrosion of zinc by corrosion morphology image is described.A scanner is used to obtain the corrosion morphology images of zinc samples.Multi-resolution wavelet analysis is performed on the selected image to obtain energy values as feature vectors.The canonical correlation analysis is used to gain the correlative coefficient between the features and the corrosion loss.The weighted features were analyzed to obtain the material loss due to corrosion by using an ANN model.The resu lts indicated that the computational methods developed for corrosion analysis could provide reasonable results for estimating material loss due to corrosion morphological image.

The continuous salt spray,alternating immersion and comprehensive environmental tests for atmospheric corrosion of aeronautical aluminum alloy were studied.By using electrochemical,SEM,XRD,XPS techniques,accelerated tests and outdoor exposure were compared.Results showed that,the comprehensive environmental test simulated characteristics of dry/wet and electrochemical process of outdoor test.Meanwhile,comprehensive environmental test also simulated the morphology of aluminum alloy atmospheric corrosion; the corrosion products in comprehensive environmental test mainly were amorphous; the kinetics of outdoor test also simulated by accelerated tests.The acceleration of the tests was discussed.

With scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) technique,properties of oxide coatings produced at different voltage on AZ91D Mg alloy substrates by micro-arc oxidation technique have been investigated.Three types of oxide coatings,passive film,micro-spark oxide coating and spark oxide coating were formed corresponding to different range of voltages.The results showed that micro-spark oxide coating exhibited the best performance of compact,homogeneous and with high resistance,comparing with other two types of oxide coatings,due to its high effective thickness.

Direct electroless Ni-P plating on the AZ91D magnesium alloy from a plating bath containing sulfate nickel was investigated.The morphology and microstructure of the electroless Ni-P coating was studied by using SEM and XRD.The electroless Ni-P coating was compact and no obvious defects.The hardness values of the Ni-P coatings were about 660 VHN and the phosphorus content of this coating was about 3.72 mass%.The deposition rate of the electroless Ni-P alloy was about 23 μm/h.The acid pickle pretreatment on the AZ91D magnesium alloy substrate provides surface pits to act as sites for mechanical interlocki ng to improve adhesion of the coating and the substrate.

The anodizing of AZ91D Mg alloy in the solution of different concentration of Na2B4O7 has been investigated by ways of voltag e-time curve,immersion corrosion experiment,polarization curve,XRD,SEM,EDS and X PS respectively.The results show that the film-forming course can be divided int o three stages:formation of dense layer before sparking,formation of porous laye r accompanied with a bit of small sparking,and porous layer stable growth along with bigger sparking.With increasing concentration of Na2B4O7 in the solut ion of the anodizing,the time and voltage of sparking formation increase,the ape rture and thickness of anodic oxide film become bigger.The anodic oxidation film contains Mg2+,O2-,Si4+ and B3+,which is composed mainly of MgO,MgSiO3 and Mg3B2O6.The concentration of Na2B4O7 plays great effect on corrosion resistance of the said film.The film has best corrosion resistance when the concentration of Na2B4O7 in the anodic solution is 160 g/L.

A sealed Devanathan-Stachurski cell as hydrogen sensor has been developed for monitoring atomic hydrogen permeation rate.Pd75Ag25 alloy is used as susceptive component and counter electrode.A piece of pure nickel is used as reference electrode.0.2 mol/dm3 KOH is filled in the cell.The background current change and signal response time were detected.The sensitivity and recurrence of the developed sensor were researched.The output of current signal from the sensor was analyzed by comparing to output of current signal from an original Devanathan-Stachurski cell.The effect of temperature impact on the senor signal was tested.The developed sensor was applied to measure the hydrogen permeation rate in field.The field result is reasonable.The working temperature of the sensor is ranged from 5℃ to 50 ℃.It is used to monitor the permeation rate of atomic hydrogen in steel wall of the equipment owing to H2S corrosion.

Three groups of specimens of CNG cylinder steels,4130X and 30CrMo,were tested in dense and moderate H2S solutions.By using modified WOL specimens loaded with bolts,we obtained KISCC in H2S environment,as well as K1C in air.The critical crack sizes of different materials in H2S environment were thus figured out,and the curves with working pressures and equivalent stress to critical crack size were plotted.The results show thatK1C of those specimens were all in a high level,thus with good fracture toughness in normal nvironment.However,KISCC in H2S environment ranged from 20% to 40% of K1C.For two groups of specimens made of CNG steel 4130X but from different vendors,their KISCC are 30% difference and their critical crack sizes are 80% difference.

The effect of NaCl deposit on the corrosion behavior of CuCr alloy at 700℃～900℃ was studied by means of metalloscope,XRD,SEM/EDX and thermogravimety.Results indicated that CuCr alloy coated with NaCl deposit suffered from seriously corrosion than in single air; the corrosion production was loose and easy to scale off; and Cr phase was easier to be eroded than Cu phase,and chromium depletion is developed in the matrix of alloy beneath the corrosion region.Effect of deformation on the corrosion of the CuCr alloy were discussed,and acceleration mechanisms of NaCl on the corrosion of CuCr alloy were also discussed.

A simulated galvanostatic occluded cell was used to investigate the effect of cathodic polarization on chemical and electrochemical states inside occluded cell (OC) of localized corrosion for cast iron in alkaline solution.It has been found that as the cathodic current passes through the cell，the pH value of the OC solution rises with prolonging of time and rising of current density;the rate of Cl- migrating out from the OC also rises with prolonging of time and rising of current density.Because of Cl- migrating out fro m OC and OH- immigrating into OC,the localized corrosion was retarded.Passing cathodic polarization in alkaline solution can make Cl- migrating more quickly ,it is more efficiency than the cast iron dipping in alkaline solution(no cathod ic polarization).

A site investigation was made on one deteriorated concrete with 6 year s age,and this concrete component was located in one tunnel of one concrete dam in Western China.Some samples were taken from the attacked concrete and were a nalyzed with XRD,SEM-EDAX and Laser Raman Spectroscopy methods.As a result,it is shown that a mushy mixture consisting of thaumasite,ettringite,gypsum and calcite occurs in the residual concrete exposed to low temperature,high humidit y,sulfate and carbonate for a long time.It is validated that the thaumasite fo rm of sulfate attack may occur in hydraulic concrete structures in Western China .In addition,the corrosion mechanism is also discussed.

By means of naturally burying specimens in soil,corrosion behavior of cable metal materials such as Cu and Al in west China inland salty soil in Kelamayi,Kuerle,Yumen and Geermu for 1 year was studied.The results showed that Cu and Al were both spot-corroded in part.High content of Cl- and SO2-4 (10.863%,0.4795%) and relatively high water content (16.68%) in pickled soil in Geermu caused bad corrosion of Cu and Al.Thereinto,the average corrosion rate of Cu was 1.1884g/dm2·a,and the pitting depth of Al was 0.74mm/a.In the inhomogeneous brown desert soil in Kelamayi,the cuspate gravel whose content was high to 51% came into contact with the Al tube tightly,which formed an oxygen-thickness-difference cell to make the Al perforate within 1 year.The pi tting depth of Al was 1.5mm/a.It was concluded that besides soil nature and the content of Cl- and SO2-4 in soil,soil edaphon was also the dominating corrosion factor.

The effects of sulfate reducing bacterial (SRB) on corrosion of Q235 steel during the evaporation of water in soils have been studied by using bacterial analyses,polarization curves,electrochemical impedance spectroscopy(EIS),scanning electron microscopy (SEM) and EDS. The results showed that the number of SRB gradually decreased with the naturally evaporating of water in soil,and the corrosion rate of Q235 steel gradually increases along with the evaporation of water in soils,and the increasing of corrosion rate in soil with SRB was more severe than that in soil without SRB.

Based on ZG06Cr13Ni4Mo (13-4)，while its chromium content being reduced to 10.61%,8.34% and 6.64% respectively,their anodic polarization curves compared with that of ZG20Cr13 have been tested in 1mol/L H2SO4 solution.Using ultrasonic vibration cavitation erosion device and Rockwell apparatus，the 13-4，the 8.5Cr-4Ni (8.5-4) and the high strength and high toughness stainless steel -SRIF have been studied on the behaviors of cavitation erosion resistance and local micro-zone elasticity respectively.Their microstructures and mechanical properties have also been investigated.The results show that electrochemical corrosion properties decrease as chromium content decreases comparing with these of the 13-4.When chromium content decreases to 8.34%,the material and ZG20Cr13 are matched in electrochemical corrosion properties,which is still in the category of stainless steel.The values of local micro-zone elasticity he of 8.5-4,13-4 and SRIF are very close.The cavitation erosion resistances of the 13-4 are higher a little than these of the 8.5-4,and these of the SRIF are obviously higher than those of 8.5-4 and 13-4.

High-iron(Fe mass%>1%)and low-iron(Fe mass%<1%)Zn-Fe-SiO2 composite coatings have been obtained from sulfate bath and chloride bath with optimum technics.Corrosion resistance,adhesion,porosity and hydrogen embrittlement of Zn-Fe-SiO2 composite coatings with different thickness have been tested systematically,and these data have been compared with the properties of Zn and Zn-Fe alloy.The results show that corrosion resistance and all other properties of Zn-Fe-SiO2 composite coatings are better than that of Zn and Zn-Fe alloy.Therefore,the Zn-Fe-SiO2 composite electrodepositing technique is superior to Zn and Zn-Fe alloy electroplating,with a great prospect in application.