Erosion-corrosion of Cu-Ni alloy pipe seriously influences the safety operation of ship and ocean engineering system. The research methods, corrosion mechanisms and the new methods for the characterization of erosion-corrosion of Cu-Ni alloys are reviewed in this paper. The influence of the composition, microstructure and sulfide inclusion of the alloy, as well as temperature, pH value, sand content, flow rate and impacting-angle of the flow media on the erosion-corrosion was analyzed. Finally,the trend of research on the erosion-corrosion of Cu-Ni alloy in sea water is prospected.

The effect of Cl^- concentration and pH values on the electrochemical corrosion behavior of Zn in saturated Zn(OH)₂ solutions, which aims to simulate the initial atmospheric corrosion environment, was studied by means of polarization curves, electrochemical impedance spectroscopy and scanning electron microscopy (SEM). The results indicated that the corrosion rate of Zn increased with the increase of Cl^- concentration, Cl^- destroyed the rust layer on the electrode, while induced pitting corrosion. Zn was in passive state at high alkaline solution, the corrosion resistance of Zn increased with the increase of pH value.

Effect of temperature and dissolved oxygen concentration on electrochemical corrosion behavior of Zn in saturated Zn(OH)₂ solutions, which aims to simulate the initial atmospheric corrosion environment, was investigated by means of weight loss measurement, polarization curves and electrochemical impedance spectroscopy. The corrosion morphology of corrosion products was detected by SEM. The results indicated that solution temperature was the main factor that affected the corrosion rate of Zn in the saturated Zn(OH)₂ solution. The corrosion rate of Zn decreased with the decrease of dissolved oxygen concentration, and increased with the increase of temperature in the saturated Zn(OH)₂ solution.

Corrosion behavior of 2205 duplex stainless steel in simulated seawater containing different concentration of NaHSO₃ has been systemically investigated by means of potentiodynamic polarization and electrochemical impedance spectrum (EIS) measurements. While the defects and the compositions of the formed passive films on the steel were characterized by Mott-Schottky and XPS respectively. The results demonstrate that the existence of HSO₃^- in the simulated seawater contributes to the increase of metal oxide content in the passive film formed on 2205 stainless steel. In the simulated seawater containing 0.01 mol/L HSO₃^-, 2205 duplex stainless steel presents the worst corrosion resistant performance, correspondingly the calculated defect concentration for the formed passive film is consistent to the electrochemical test results. The oxidation of HSO₃^- induces the formation of HSO₄^- in aqueous solution, which will give rise to the releasing of hydrogen ions, leading to the increase of acidity of the solution and thus induces the damage of the passive film on 2205 stainless steel. However, when the concentration of HSO₃^- in simulated seawater is less than 0.01 mol/L, the corrosion resistance of the steel will rise again. This is because the competitive adsorption between HSO₃^- and Cl^- on the 2205 stainless steel surface can inhibit the adsorption of Cl^-, which then results in the decline of the pitting corrosion probability.

The pore solutions of different periods of concrete lifetime were simulated by varying the pH value, then the corrosion performance of 304SS was studied by means of polarization curves, EIS, M-S testing technology in the simulated concrete pore solutions. It shows that the corrosion resistance of the formed passive film will decrease with the decreasing of pH value and increasing of the chloride ion concentration. The corrosion resistance of passive film formed in the solution with pH=13 is much higher than that in solutions with pH=9 and pH=11. It is noted that the insoluble corrosion product formed in solutions with higher pH spilled from corrosion pits will damage the passive film. The passive films formed in solutions with different pH values show characteristics of N-type semiconductor under open circuit potential, however the electrical resistance of the passive film formed in chloride saturated solutions with pH=13 is much higher than those with pH=9 and 11. It is expected that the concrete carbonation and the permeation of chloride ion may occur during the service of stainless steel reinforced concrete structures in marine environments, which can have important impact on the passive film of 304SS, such as reducing the stability of the passive film and/or increasing the corrosion-susceptibility of the steel.

The corrosion inhibition effect of phytic acid conversion coatings formed on Q235 carbon steel was evaluated by potentiodynamic polarization curves and electrochemistry impedance spectroscopy. The phytic acid conversion coating on carbon steel surface prepared in 0.06 mol/L pH 7.0 phytic acid solution for 1 h has the best inhibition effect with inhibition efficiency up to 96.7%. Though the phytic acid conversion coating adheres to the carbon steel surface through physi-sorption, the coating possesses fairly well adhesiveness to the substrate. SEM and XPS results show the prepared coating on carbon steel surface is a composite coating of phytic acid conversion coating and Fe₂O₃ passivation film, while the two components have synergistic effect.

A water-based chromium-free Dacromet coating was prepared with powders of Zn and Al as filler and silane A-187 as film forming material. The coatings were characterized by means of SEM with EDS and XRD, while their corrosion performance was investigated by using potentiodynamic measurement, NSS test and AC impedance spectra. The results showed that the water-based chromium-free Dacromet paint had excellent stability with no obvious change even after storage at 50 ℃ for 48 h; the surface of the applied coatings was smooth and compact without defects, while no tarnish spots could be observed after 480 h salt spray test. The E_corr of the water-based chromium-free Dacromet coating shifts positively while its I_corr is two magnitudes lower in comparison to those of the bare substrate which indicated that the water-based chromium-free Dacromet coating had excellent corrosion resistance.

Hexagonal boron nitride doped waterborne epoxy coating was prepared by incorporating the water dispersed h-BN into the waterborne epoxy resin with a high speed stirring. The dispersity of h-BN in water was characterized by transmission electron microscopy, scanning probe microscopy and scanning electron microscopy. The anticorrosion performance of the waterborne epoxy coating doped with different among of h-BN was investigated by means of electrochemical impedance spectroscopy (EIS), open circuit potential (OCP) and potentiodynamic polarization measurement. The results indicated that h-BN existed within relative thin multilayer in the water, which was beneficial to the formation of dense physical barrier composited of h-BN, thus slowing down the diffusion rate of corrosive medium in the coating and improving their anticorrosion performance. Meanwhile, in comparison with the pure epoxy coating, the epoxy coating with 2%h-BN exhibited extremely high impedance modulus and low corrosion current density, indicating its excellent corrosion performance.

Amorphous Ti-B based coatings with various densities were deposited on various substrates, i.e. Eagle glass, silicon slice and NdFeB alloy respectively, by means of magnetron sputtering, and then their structure, hardness and corrosion resistance were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), nanoindentation tester, and Modulab electrochemical workstation. The results show that the prepared coatings are amorphous with densities varying in a range 4.04, 4.27 and 4.61 g/cm³ through controlling the processing parameter. Their cross-sectional morphologies show that all the coatings are homogeneous, compact and smooth without features of columnar structure existed in the common PVD coatings. The hardness and corrosion resistance of coatings are closely related to their densities. When the coating density is increased by 14.11%, the hardness is enhanced by 49.01% for the coatings deposited on silicon slice, and the corrosion current density is decreased to 1/3 of that of the one with density 4.04 g/cm³, for the coatings deposited on NdFeB. Correspondingly, the hardness and plastic index are 30.1 GPa and 0.48 respectively for the coating with density 4.61 g/cm³ on silicon slice. Meanwhile, all the coatings with various densities can provide corrosion protection for NdFeB substrates. With the increasing coating density the free corrosion potential shifts to the positive direction and the relevant free corrosion current density decreases gradually for the Ti-B coatings on NbFeB, in the contrast, the bare substrate is just the opposite. The coating with density 4.61 g/cm³ on NdFeB exhibits a free corrosion current density 1.34×10^-6 A/cm², about 1/8 of that of NdFeB substrate, and free corrosion potential -0.689 V, 0.220 V nobler than bare substrate in the 3.5% (mass fraction) NaCl solution. It follows that the amorphous and hard Ti-B coatings can provide good protectiveness to the NdFeB alloy in environments such as NaCl solution.

Corrosion behavior of 7050 Al-alloy, which was pre- anodized in electrolyte of boric-and sulfuric-acid, was assessed through field exposure in industrial-marine atmosphere for 2 a at Qingdao area. The corrosion rate was acquired from the relevant mass-lost data. The surface morphology, distribution of elements and the phase compositions of corrosion products were characterized by SEM, EDS and XRD, as well as the protectiveness of product scale and anodic film was evaluated by using EIS. It is indicated that the bare Al suffered from severe exfoliation corrosion with annual corrosion rate of 5.92 μma^-1, and its corrosion product mainly consists of Al(HSO₄)₃6H₂O, Al₄SO₄(OH)105H₂O and NaAlSi₃O₈; the formed corrosion product scale on the bare Al can provide protectiveness to the substrate to some extent, however, the anodized film can provide much better protectiveness in comparison with the formed oxide scale on bare Al.

The tribocorrosion behavior of 2024 Al-alloy in artificial seawater was studied, using a pin-on-disk reciprocating friction and wear tester integrated with a potentiostat for electrochemical test. The result showed the material loss caused by wear-corrosion processes without cathodic protection was larger than that with cathodic protection, indicating synergistic effect of mechanical wear and corrosion process. The ratio of the mechanical wear to the total degradation ranged from 70.3% to 98.2%, which indicated mechanical wear component prevailed over the corrosion component. The proportion of the mass loss caused by wear-corrosion synergism to the total degradation was between 1.8% and 29.7%, and therefore the wear-corrosion synergism could not be neglected.

The effect of Zinc addition on microstructure and corrosion property of the as-extruded Mg-13Gd-2Cu alloy were studied using scanning electron microscope (SEM) equipped with energy dispersive spectroscope (EDS), electron microprobe analysis (EMPA), X-ray diffractometer, immersion test and electrochemical measurements. The result show that the Mg-13Gd-2Cu alloy consists mainly of α-Mg, Mg₅(GdCu)₁ and elemental Gd phase. When 2%(mass fraction) Zn added in the Mg-13Gd-2Cu alloy, a long period stacking order (LPSO) phase Mg₁₂(GdCuZn)₁ forms. The presence of the LPSO phase enables the corrosion rate of the alloy to be decreased from 1.51 mm/d to 1.23 mm/d. The results of electrochemical measurements with various scan rate indicate that the free-corrosion potential (E_corr) shifts positively and the free-corrosion current density (I_corr) decreases about 0.18 mAcm^-2 for the Mg-13Gd-2Cu-2Zn alloy. The reduction of I_corr proves that Zn addition can enhance the corrosion resistance of Mg-13Gd-2Cu alloy.

The simulated intercritical HAZ (ICHAZ), fine grained HAZ (FGHAZ) and coarse grained HAZ (CGHAZ) of weld joints for two Nb containing steels were prepared by means of heat treatment. Then their microstructure and distribution of nano-sized precipitates were characterized by means of optical microscopy and transmission electron microscopy. Their corrosion behavior in simulated seawater environments corresponding to shallow sea and deep sea of 600 m below sea level respectively were studied by conventional electrochemical techiques and immersion tests. It's shown that the corrosion rate of ICHAZ and CGHAZ is much higher than that of FGHAZ. What's more, with the addition of Nb, the microstructural homogeneity of the steel is improved and the corrosion products films formed on the steels become much compact, thus enhancing their corrosion resistance. Besides, the nano-sized NbC precipitates can act as traps for capturing hydrogen, thus enhancing their corrosion resistance also in the seawater of deep sea.

The corrosion resistance for different zones of welded joint of A710 steel was investigated by electrochemical methods, mass loss measurement, morphological observation and component analysis. Results show that the three zones of the welded joint, namely base metal (BM), heat affected zone (HAZ) and weld seam (WS), exhibit different features in microstructure. BM consists mainly of ferrite, and HAZ consists mainly of ferrite, bainite and M-A islands, while WS consists mainly of bainite and less acicular ferrite. Among others the zone of WS shows the highest electrochemical activity and average corrosion rate in 3.5%NaCl solution. After 16 d immersion, the corrosion product on WS surface is loose and lack of protection, therefore, the deeper corrosion pits and grooves were observed on the WS zone. In contrast, the corrosion products on BM and HAZ surface are compact and have better protectiveness, consequently, the substrates of BM and HAZ suffered from slighter corrosion.

A superhydrophobic surface film on Q235 steel substrate was prepared by chemical etching and then applying a film with low energy. The surface roughness and wettability of the steel prepared by chemical etching were characterized by scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and contact angle measuring instrument. The concentration of nitric acid in the etching liquid plays a major role for the surface roughness of the steel. With the increase of the nitric acid concentration in the etching solution, the surface roughness of the steel increased in the beginning stage and then decreased. Among others, the steel surface etched with 20%(mass fraction) HNO₃ is the best for further processing. Then the superhydrophobic surface film was then fabricated by applying the low surface energy film of polydimethylsiloxane (PDMS) on the chemical etched steel. The result revealed that the as-prepared superhydrophobic surface exhibits a contact angle of 163° and excellent corrosion resistance in 3.5%NaCl solution, which may be attributed to the synergistic effect of an air film on the superhydrophobic surface, the PDMS film itself and the hydrophobic steel surface.

The electrochemical performance of domestic Ti-alloy TA2, an imported Ti-alloy condenser tube and 316L stainless steel were studied comparatively in seawater by means of electrochemical measurements and slow strain rate method with emphasis on the effect of different polarization potentials on hydrogen embrittlement and the evolution characters of microstructure of the alloys, so that the reasonable protection potential range for condenser in seawater was obtained. The results revealed that galvanic corrosion occurred for the couple of 316L/Ti in seawater, which accelerated the corrosion of 316L stainless steel. When cathodic protection is applied to the above couple, the potential of Ti should be better maintained within a range of -0.50~-0.65 V (vs Ag/AgCl). Based on the above results, the cathodic protection design was conducted for the desired condenser, for which FeMn alloy were proposed as anodes to protect the condenser and worked effectively to ensure the long-term and safe operation.

The corrosion behavior of Incoloy825 alloy in 3.5%NaCl solution was studied in a temperature range 30~60 ℃ by polarization curve measurement, electrochemical impedance spectroscopy (EIS) and immersion test. The results show that the corrosion degree of Incoloy825 alloy increases with the increase of solution temperature, meanwhile, the size and density of corrosion pits increase. Moreover, the corrosion form is changed from general corrosion to localized pitting corrosion. The corrosion rate of the alloy increases with the increased temperature, which may be due to the synthetically effect of the two opposite factors i.e. the block effect with reducing oxygen and the stimulation effect with enhancing ion activity on the electrode process. Whilst the activity of chloride ion may play an important role in the acceleration of the corrosion process.

Molybdate intercalated ZnAlCe-hydrotalcite (ZnAlCe-MoO₄ LDH) was synthesized by using solvothermal method, and the preparation parameters such as n(Al³⁺)/n(Ce³⁺) ratio, reaction temperature and crystallization temperature were optimized by single factor and orthogonal experiments. The surface morphology and structure of the prepared ZnAlCe-MoO₄ LDH were characterized by SEM, XRD and FT-IR methods. The inhibition behavior of ZnAlCe-MoO₄ LDH for Q235 steel in 3.5%(mass fraction) NaCl solution were investigated by EIS and XPS. Results show that the synthesized ZnAlCe-MoO₄ LDH presents laminar microstructure with the thickness of 30 nm. The optimum preparation conditions are n(Al³⁺)/n(Ce³⁺) ratio of 6:1, reaction temperature of 60 ℃and crystallization temperature of 100 ℃. The inhibition effect of ZnAlCe-MoO₄ LDH on the corrosion of Q235 steel in 3.5%NaCl solution may be ascribed to the reduction of chloride concentration in 3.5%NaCl solution owing to the anion exchange with molybdate, the formation of passive film with the composition of ferrous or iron molybdate and the deposition of film consisted of zinc and cerium hydroxides.

The corrosion inhibition of dodecylamine on carbon steel in NaCl solution with continuous aeration of CO₂ was studied by means of a rotating disk with electrochemical methods. Results show that the inhibition efficiency of dodecylamine can reach 93.44% with the inhibitor dose of 60 mg/L in the solution. In the blank NaCl solution without inhibitor, the corrosion rate of the steel increases with the increase of the rotation speed. In the solution with the inhibitor dose of 80 mg/L, the corrosion rate of the steel reaches the highest by rotation speed 500 r/min, and then the lowest by 2000 r/min. The corrosion behavior of carbon steel has changed obviously in the presence of inhibitor. The corrosion rate increases with the increase of inhibitor dose, and the inhibition efficiency can reach 87.93% in the presence of inhibitor dose of 80 mg/L by 1500 r/min.

Effect of the presence of static magnetic field on the microorganism induced corrosion of 304 stainless steel (304SS) was studied. Results show that the SMF of 150 mT did not significantly affect the growth curve of planktonic SRB, but it delayed the formation of sessile SRB. The results of electrochemical measurements and surface analysis indicated that the formation of SRB biofilms could be inhibited and the adhesion of SRB biofilms could be declined on the steel due to the presence of SMF, while the effect of the SMF of 4 mT was stronger than that of 150 mT. X-ray photoelectron spectroscopy (XPS) found that the dominated corrosion product was FeS in the absence of SMF, in other words, the presence of SMF promoted the formation of iron oxides. It is concluded that the static magnetic field (SMF) could be a promising method to prevent the adhesion of sulfate reducing bacteria (SRB) biofilms on steel surface, and therefore to inhibit SRB related microbiological influenced corrosion (MIC).

Bacillus vietnamensis was collected from the East China Sea at the corrosion test site of Zhoushan Island, Zhejiang Province, and then separated as a bacterial strain. The effect of Bacillus vietnamensis on the corrosion of 2507 duplex stainless steel (2507 DSS) in sea water was investigated using different electrochemical-, surface analysis- and spectroscopy-methods. The results showed that the open circuit potential shifted to negative direction in the presence of this bacterium because of the activation of the 2507 DSS surface. The corrosion rate is measured by potentiodynamic polarization method and demonstrated that the corrosion rate of 2507 DSS increased in the presence of the bacterium. FE-SEM images also confirmed the above results and showed a biofilm formed on the 2507 DSS surface when exposed to Bacillus vietnamensis. FTIR spectrum showed several peaks at the range of 900~1200 and 1500~1600 cm^-1 which are related to exopolysaccharide and proteins. A wide peak also observed at 2800~2900 cm^-1 which makes this bacterium different from other bacteria. It is surprising that these peaks only can be observed after long exposure times and might be related to the biofilm formation on the steel surface. EIS results also showed the presence of biofilm on the surfaces. It can be concluded that the heterogenic biofilm and iron oxide on the steel surface accelerated the corrosion process of 2507 DSS surfaces.