In the present work, Ti-Al-N coatings were deposited on 1Cr18Ni9Ti substrates at a low synthesis temperature using arc ion plating(AIP). The effects of nitrogen flow rate and post-heat treatment on the microstructure of the coatings were investigated. The results show that no Ti₂AlN phase forms in all the as-deposited coatings. The coatings are possibly composed of Ti₃AlN inverse perovskite phase, TiN, α-Ti, fcc-Al and Ti_xAl_y intermetallic phase. Ti₂AlN phase can be detected in the annealed coatings in a given condition. It has been found that the nitrogen concentration in the coatings and the annealing temperature play a key role in the phase formation. The formation of Ti₂AlN phase is suppressed by the increment of nitrogen concentration and promoted by the enhancement of annealing temperature. TEM results indicate that the formation of Ti₂AlN phase is accompanied by the microstructure evolution from strong layered structure to fine equiaxed crystals in the process of heat treatment.

Ti_0.5Al_0.5N/Ti_0.7Al_0.3N double-layered film and Ti_0.6Al_0.3Si_0.1N film were deposited on Ti6Al4V alloy by the arc ion plating (AIP) method. It was found that the deposition of the films of the two types significantly improved cyclic oxidation resistance of the Ti6Al4V alloy at 550℃ and 650℃, due to the formation of a thin and continuous Al₂O₃-rich scale. At 750℃, a good cyclic oxidation resistance still remained for the Ti_0.6Al_0.3Si_0.1N-coated Ti6Al4V but not for the Ti_0.5Al_0.5N/Ti_0.7Al_0.3N-coated alloy.

An environment-friendly phosphate film was obtained on the AZ31 magnesium alloy surface via chemical deposition methods. The morphology, compositions and phase compositions of the film were examined using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD). The results show that a dense, uniform and crack-free phosphate film can be prepared using the solution with free of chromate, fluorides and nitrite. The phosphate films are mainly composed of MnHPO₄•2.25H₂O, The film thickness is between 12 μm and 15 μm and the compositions consist of O, Mg, P, Mn and Al. the film hardly appears corrosion phenomenon for 72 h in the neutral salt spray test (NSS), and the time could arrive 204 h after the plus paint. The test results indicate that the phosphate film is of good corrosion resistance. Potentiodynamic polarization curves prove that the E_corr with the film is shifted positively 111 mV (vs. SCE); the I_corr is decreased at least by three orders compared with that of the bare substrate AZ31 respectively. The results show also that the existence of the film has a great inhibitive action on anodic dissolution and restraint action on the cathodic hydrogen evolution, which will effectively improve the corrosion resistance for magnesium alloy AZ31.

CrZrCu alloy coating was deposited on the steel substrate using the cold spray technology. The morphologies of CrZrCu alloy coating were investigated by means of scanning electron microscope (SEM). The corrosion behaviors of CrZrCu alloy coatings in seawater were characterized by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The X-ray diffraction (XRD) results of corrosion products and scanning electron microscopy (SEM) analysis of corrosion surface were used to comparatively investigate the corrosion properties of CrZrCu alloy coating. The results indicated that CrZrCu alloy coating has a more dense microstructure. CrZrCu alloy coating has good corrosion resistance, and the corrosion rate of CrZrCu alloy coatings retained a low level with time.

Magnesium alloys after microarc oxidation (MAO) pretreatment were directly electroless Ni plated by using NiSO₄ solution, meanwhile, any traditional pretreatment, including alkaline washing, acid washing and activation, etc., was used. The microstructure and composition of nickel layer were characterized. The effect of MAO pretreatment on the thickness, hardness, electrical conductivity and corrosion resistance of nickel layer were investigated. The results indicate that the layer which contains Ni and P is composed of cellular particles. MAO pretreatmely affects the thickness and electrical conductivity of nickel layer significantly. The thickness of nickel layer fastly increases but the sheet resistance of the layer rapidly decreases when the thickness of MAO film increases from 3 to 7 μm. Furthermore, the results of polarization curve test reveal that when the thickness of MAO film is 15 $\mu$m, the corrosion potential of the obtained electroless nickel plated magnesium alloy is the highest, and the corrosion current is the lowest. The results of 48 h salt spray test show that the corrosion resistance of electroless nickel plated magnesium alloy with MAO pretreatment is much higher than that of electroless nickel plated magnesium alloy with traditional pretreatment and magnesium alloy substrate.

The wire beam electrode (WBE) was used to study the distributions of the electrochemical parameters of 304 stainless steel under a droplet of NaCl as well as their variations with the corrosion time. It was found that the distributions of the corrosion potential and the galvanic current were inhomogeneous with local anodic and cathodic zones appeared randomly. Moreover, the polarity of local zones changed with the evolution of corrosion process. The corrosion degree and inhomogeneity increased firstly, then decreased afterward with the increase of time. Stainless steel exhibited the highest anodic current density after exposure for 12 hours.

Cerium oxide thin films were anodically electrodeposited onto 304 stainless steel substrates. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to investigate the effects of different deposition conditions, including different concentration of ligand and different kinds of ligand-cations and O₂, on the surface structure of the anodically obtained CeO₂ film. The results showed that NH₄⁺ can refine the crystallites of CeO₂ film, high concentration of CH₃COONH₄ ligand and the deaerating process of electroplating solutions can make the obtained CeO₂ film compact. Under the deaerating conditions, nanocrystalline anodic CeO₂ film with the micro-crystallite diameter between 5~10 nm has been successfully obtained from the solution containing 0.1 mol/L Ce(NO₃)₃ and 0.2 mol/L CH₃COONH₄.

Distribution of Ce-Mn conversion coating was analysed with electron probe micro analysis,energy disperse spectroscopy, X-ray photoelectron spectroscopy analysis, respectively. X-ray diffraction was used to study the features of the phase composition of the conversion coating and the sediment in the solution containing HF₂^- ions. The results show that the element F does not exist in the Ce-Mn conversion coatings, and HF₂^- does not participate in the growth process of the coating. The main purpose of HF₂^- ions was in the initial stage. Al matrix and its oxide film (Al₂O₃) in the surface of Al alloy were dissolved priority, so that cathode district which conducive to the formation of the coating exposures rapidly to the solution. Simultaneously, the total [AlF₆]^3- in the solution is less than 1.8 mmol/L, completely dissolved.

Activation performance and dissolution behavior of Al-Zn-In-Mg-Ga-Mn sacrifice anode under condition of natural corrosion and coupled with 7A52 aluminum alloy was investigated by electrochemistry impedance spectrum technology, mass loss method and SEM analysis technology. The result showed: the corrosion rate of 7A52 which was protected by sacrificial anode was decreased at a certain extent. The sacrificial anode corrodes uniformity, and corrosion products fall off easily. Al-Zn-In-Mg-Ga-Mn sacrifice anode in natural corrosion occurs localized corrosion and dissolves non-uniform, which the active pots was covered by oxide film and corrosion products, and the corrosion reaction was prevented.

The microbiologically influenced corrosion behaviors of marine microorganism on 316L SS were studied by the immersion experiments in the nature seawater using the open circuit potential (E_ocp), electrochemical impedance spectroscopy (EIS), potentiodynamic anodic and cyclic polarization curves, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) methods. It was observed that marine biofilm was formed by microorganisms on the surface of stainless steel. It was confirmed that E_ocp of 316L SS in nature seawater shifted in noble direction nearly 450 mV. However, in sterile seawater, E_ocp was stable in experimental period. The presence of marine biofilms on the stainless steel played a role in inhibiting the initial corrosion according to the decrease in corrosion current densities obtained from the polarization curves, the increase of the polarization resistance (R_p) obtained from EIS and the increase of the pitting corrosion potential from the potentiodynamic polarization by the comparison test of 316L SS immersed in nature seawater and sterile seawater. It was suggested that marine biofilm and its metabolites improved the superficial anticorrosive properties of 316L SS by inhibiting the anodic dissolution behavior of stainless steel.

The crevice corrosion mechanism of Q235 carbon steel in soil leaching solution was studied, using a rectangle blind side device. The width of its aperture is 0.5 mm. The soil leaching solution was prepared in two groups for comparison: with SRB (sulphate reducing bacteria) and without SRB, both being investigated separately. The corrosion behavior of the steel was studied by electrochemical, microbiological and surface analysis methods. Electrochemical impedance spectroscopy (EIS) was measured. The results show that, the capacitive arc of the steel in bacteria containing solution is smaller than that in the aseptic solution at the same stage and the corrosion rate in bacteria containing solution is smaller than that in the aseptic solution. The results declare that SRB promotes the corrosion of the steel. At the same time, along with the aperture increasing, the capacitive arc increases at first, then decreases, and the corrosion rate of the bacteria containing solution is greater.

The corrosion behaviors of 321 and 316L austenitic stainless steel in high-temperature naphthenic acid medium were investigated by pipe flow. The influence of the erosion angle on naphthenic acid corrosion resistance of stainless steel was mainly analyzed. The results revealed that naphthenic acid corrosion rate increased with increasing temperature. The corrosion rates of erosion angle 90° is greater than 0° at the same temperature. The present experimental data and API 581, on-line monitoring data are close. Similar results were obtained after the test data compared with the empirical data of API 581 and on-line monitoring data. It was shown that naphthenic acid corrosion is most severe in areas of highest turbulence.

The key technology of bronze protection is to control and exterminate the harmful “powdery rust”. Based on the character that copper chloride is easy to decompose and volatilize, this paper analyzed Cu₂(OH)₃Cl made from the surface of bronze samples and CuCl using thermal analyzer and X-ray diffraction(XRD). The results showed that the Cl^- can be outrooted if copper chloride ore were heated up to 350℃ in the air. Besides, CuCl volatilized easily and the reaction accelerated at 600℃ and finished at 789℃

Based on the heat treatment process test of G105 pipe materials, the influence of different heat treatment on material microstructure and properties was studied by using electrochemical test and slow strain rate tensile test. The results show that material properties can meet the need of G105 pipe technical requirements after quenched at 890℃ and tempered at 620℃ or quenched at 890℃and tempered at 580℃; tempering temperature impacts the mechanical properties of materials, and the higher the tempering temperature, the stronger the ductility and the toughness; the microstructure after quenched at 890℃ and tempered at 620℃ is superior to that quenched at 890℃ and tempered at 580℃, and the former has better corrosion resistance.

The corrosion behavior and regularity of copper T2 and brass H62 exposed in tropical maritime atmospheric environment in Xisha Islands for 1 month, 3 mouths and 6 months were studied through field exposure test. The surface and cross-sections morphologies of corrosion products were observed using SEM, energy dispersive spectromet (EDS) and X-ray diffraction (XRD) analysis were used to obtain the detailed information of the corrosion products. Electrochemical impedance spectroscopy (EIS)measurements were made for copper T2 and brass H62 specimens. The results showed that obvious localized corrosion occurred for copper T2 and brass H62 specimens in maritime atmospheric environment in Xisha Islands. The existence of O and Cl^- is the main reason for the initial corrosion. The relatively high relativity humidity, temperature, Cl^- amount, long sunshine, and the existence of dust accelerated the corrosionm of copper T2 and brass H62 specimens. The main corrosion product for copper T2 is Cu₂O and for brass H62 are Cu₃Cl₄(OH)₂ and Zn₅(OH)₈Cl₂•H₂O.

To observe the aging performance of AF magnetism coatings with different substrates, the exposure test in Xisha marine atmospheric environment carried out, and series of performance evaluation such as gloss, color, the degree of chalking and SEM were applied to test the transformation of surface topography and properties, and the contrast was completed. The results were: the anti -weathering of AF magnetism coating was wrong in outdoor atmospheric environment, and the anti-weathering of AF magnetism coating was preferable in indoor atmospheric environment; In indoor atmospheric environment the anti-weathering of AF magnetism coating with LY12-CZ substrate and Q195 substrate was better than the anti-weathering of AF magnetism coating with LF6M substrate; The primary causes of coating aging are the illumination, temperature and humidity, and the strong illumination, high temperature and high humidity of Xisha accelerate the aging of coating.

The causes of failure of plungers sprayed by Ni-base alloy were investigated by means of scanning electron microscopy (SEM) and X-ray diffraction meter(XRD). The results indicate that sulfuration and oxidation corrosion occurs in Ni-base alloy coatings of plungers operating in S-O-C mixture condition in oil wells, the complicated loosing and peeling sulfide and oxide salt-like microstructure phase, such as CrS, Cr₃S₄, Ni₃S₂, FeS, NiO and other phase are produced to enlarge the diameter of the plungers and make the plungers match difficultly, the hardness of the coating surface remarkably decreases. The corrosion mechanism of Ni-base coatings was studied to prove that the sulfuration resistance and comprehensive applications are dramatically improved by adding Mo and Nb which can refine the grain size and have excellent sulfuration resistance.