Abstract Gradient (Ti,Al)N coating was deposited on 1Cr11Ni2W2MoV stainless steel for aero-engine compressor blades by arc ion plating. The XRD results showed that the gradient coating had a B1(NaCl) structure with (220) preferred orientation. The elemental gradient distributions of Ti and Al were confirmed by electron probe microanalysis (EPMA). The oxidation test of the coatings was carried out by heating the samples at temperatures of 700℃ and 800℃ respectively in the air for selected time. The surface and cross-sectional morphologies of the as-deposited and oxidized coatings were investigated by scanning electron microscopy (SEM/EDS). The oxidation results indicated that the gradient coatings were protective at 700℃ for long time and at 800℃ for short time. It was found that protective layers rich in amorphous alumina formed on top of the gradient (Ti,Al)N film during the elevated temperature oxidation which protected the film from further oxidation.

A two-step electrosynthesis of polypyrrole film （Ppy） on 1Cr18Ni9 stainless steel and Pt substrates was performed based on the self-catalysed property of Ppy synthesis， and smooth conductive polymer film was obtained. The redox character of Ppy and corrosion behavior of stainless steel protected by Ppy film in 3.5% NaCl solution were investigated.Results show that the reduction of Ppy contains two processions including anion de-dopping and cation insertion， and that reversible oxidation （doping） can only occur at low potential. It is con?鄄firmed that stainless steel corrosion can be inhibited effectively by Ppy film and the physical barrier is not the major factor of corrosion protection.It is possible that Ppy coating has a catalytic effect on passivation of metal with protective oxide layer， and corrosion could be inhibited.

Polyaniline （PANI） films are deposited on aluminum substrate through electrochemical process and the corrosion resistance of PANI films is studied. The results show metallic nickel of nonelectrolytic deposition on the aluminum surface can catalyze electropolymerization of aniline.The proper upper scanning potential through cyclic voltammetry is not more than 0.7 V（vs. Hg/Hg2SO4）； the polymerization potential range through potentio?鄄static is between 0 and 0.45 V（vs. Hg/Hg2SO4）； the current density through galvanostatic is not more than 0.3 mA/cm2；the proper electrolytic pH value is at range of 2 to 3.The potentiodynamic polarization curves in 0.5 mol/L sodium chloride solution show that the pitting corrosion potentials of aluminum electrodes coated with PANI through cyclic voltammetry，potentiostatic or galvanostatic method shift toward positive direction as compared with pure aluminum electrode.The PANI coating could improve the pitting corrosion resistance of aluminum and its alloy.

Abstract The electrochemical behavior of HAl77-2 brass alloy in flowing seawater was studied by using rotating ring electrode. EIS and linear potential sweep were tested at different flow velocities. The results show that the EIS of HAl77-2 brass alloy in seawater at different flow velocities presents different characteristics and the relationship between corrosion behavior and flow velocity was analyzed.

The lipophilicity modification of Cu2O is studied, using organic agents as modifying agent to improve the compatibility and dispersion ability of Cu2O in oleoresin. It was found that the modifying effect is arranged as 3-(trimethoxysilyl) propyl methaciylate(TMSM), trimethoxy- vinylsilicone(VTS) , polyvinyl alcohol（PVA）in decreasing order. The best weight ratio of TMSM to Cu2O is 1:50. The modifying reaction time is about 60min and strong stir does good to the modification. The antifouling paints using lipophilicity modified Cu2O as main antifoulant have better subsidence-resistance and attachment ability.

Nanocrystallized 309 stainless steel coating has been fabricated on glass substrate by DC magnetron sputtering. The coating, with an average grain size less than 50 nm, had ferritic （bcc） structure rather than the austenitic （fcc） structure of the bulk steel. The electrochemical corrosion behavior of the nano-crystalline （NC) coating and the bulk steel in solutions of 0.25 mol/L Na2SO4 + 0.05 mol/L H2SO4 and 0.5 mol/L NaCl + 0.05 mol/L H2SO4 was investigated by using potentiodynamic polarization,potentiostatic polarization and capacitance mea?鄄surement. The results showed that the corrosion behavior of the NC 309SS coating and 309SS bulk steel depend?鄄ed on the composition of the solutions. In the Na2SO4 solution there was only a little difference between the corro?鄄sion resistance of the passive films on the NC coating and the bulk steel. However, in the solution with chloride ions, the localized corrosion resistance of 309SS was greatly enhanced by nanocrystallization due to the formation of a compact and stable passive film on the NC coating. The electronic structure of the passive film formed on the NC coating and on the bulk steel was analyzed by means of capacitance measurements, and a corrosion mecha?鄄nism is proposed.

The influence of concentration of fluoride ion on the pitting corrosion behavior of 316SS has been in?鄄vestigated by means of measuring the critical pitting temperature （CPT) in 0.1 mol/L NaCl solution. The results showed that the CPT decreased and the open circuit potential also decreased with increasing concentration of flu?鄄oride ion. Metastable pitting occurred just below the CPT， while stable pits could only be formed above the CPT. The morphologies of the pits below and above the CPT had been obtained by scanning electron microscope （SEM).

The bacteria in seawater were cultured in batch and the corrosion behavior of 304 stainless steel in the medium of marine microorganisms was investigated by polarization curves and electrochemical impedance spec?鄄troscopy， etc. Experimental results show that the stainless steel current density of anodic polarization in culture medium with bacteria is higher than that without bacteria， and the impedance value in medium without bacteria first decreases then increases， while in medium with bacteria decreases all through. In conclusion，the bacteria in seawater accelerates the corrosion of 304 stainless steel and induces pitting corrosion to the 304 stainless steel.

The effect of sulfate-reducing bacteria (SRB) on corrosion behavior of HSn70-1A alloy were studied by electrochemical, microbiology and surface analysis methods. The results showed that the free corrosion poten?鄄tial of the alloy shifted negatively when SRB was inoculated,the polarization resistance decreased obviously, which corresponds to an increased corrosion rate. The serious pitting corrosion occurring on the alloy surface un?鄄der the action of SRB was observed by SEM. Furthermore, influence of medium flow characteristic and material surface appearance on corrosion behavior of HSn70－1A alloy under the biofilm of SRB were researched. It was showed that the average corrosion rate was higher and the SRB count in the biofilm was less when test piece was immersed in the flowing batch culture medium inoculated with SRB than in the static batch culture medium in?鄄oculated with SRB . Thus the flow of medium could speed up the corrosion rate . After being coated in the mix?鄄ture corrosion inhibitor of MBT and BTA beforehand, the copper electrode had more positive free corrosion po?鄄tential and higher linear polarization resistance in the culture medium inoculated with SRB than the one without being coated, which demonstrated that the resistance of HSn70－1A alloy against microbiologically influenced cor?鄄rosion increased obviously.

New Corrosion inhibitor named 2,5-bis（2-hendecyl）-1,3,4-oxadiazole（HOX） was synthesized and characterized.Its inhibiting behavior for carbon steel in 1mol/L and 2 mol/L hydrochloric acid was in-vestigated by means of weight loss, potentiodynamic polarization curves and electrochemical impedance meth-ods. The results show that it behaves excellent as inhibitor at very low concentration. HOX suppressed both cathodic and anodic processes of steel corrosion in 1 mol/L and 2 mol/L HCl solution by chemisorption on steel surface. It also indicates the adsorption is according to a Langmuir isotherm adsorption model.

The fractography of high strength aluminum alloy LY12CZ riveted specimen with coating was investi?鄄gated after corrosion fatigue tests under stress in 3.5% NaCl solution. Fracture features like fatigue striation， dimple， cleavage， and intergranular fracture were observed. The corrosion fatigue mechanism was controlled by anodic dissolution. The failure mode was multi-crack fracture. Cracks were initiated from every rivet holes. The principal crack with longer propagation length and varying positions finally converged with other cracks and led to fatigue fracture.

The research status of numerical calculation of cathodic protection potential distribution is discussed, including the building of mathematical model, the chosen of boundary conditions and numerical calculation methods. The problems exiting in this field and the developing directions are proposed.

Currently,along with the application of aluminum matrix composites,studies of corrosion resistance would be necessary. From the comprehensive review presented in this article, corrosion resistant properties and protection methods for three materials Cf /Al, SiC/Al, Al2O3/Al are pointed out. There are three kinds corrosion mechanism for Cf /Al composites, galvanic corrosion, hydrolysis of Al4C3, denudation on the interface, the gal?鄄vanic couples corrosion is standing out. The surfaces between SiC and aluminum come forth corrosion distinctly from SiC/Al composite interface, because in evidence of pitting and crevice corrosion there, which would be formed denudation. Al2O3 is insulator,none galvanic couples come from Al2O3/Al composite, it is higher corrosion resistance than Cf /Al composite and SiC/Al composite.It is concluded that the surface coating on the composites, the reinforcement surface coatings,alloyed in the Al-based were the improvement methods of corrosion resis?鄄tance. It is valuable to improve corrosion resistance and protection for aluminum metal matrix composites.