The current status of the study on corrosion behavior of friction stir welded (FSW) aluminum alloy was reviewed, the corrosion methods including stress corrosion test, salt spray test, immersion test, electrochemical test and gel visualization test were discussed emphatically, and the existing problems in corrosion methods were pointed out, the corrosion mechanism and the measures about how to improve the corrosion properties of FSW joints were also analyzed.

Potentiodynamic polarization curves, cyclic polarization curves and electrochemical impedance spectroscopy (EIS) were used to investigate the corrosion behaviors of 904L stainless steel in concentrated sulfuric acid containing hydrofluoric acid. The result shows that the corrosion of 904L stainless steel in concentrated sulfuric acid is inhibited when the mass fraction of hydrofluoric acid is less than 2%; while the corrosion is promoted when the mass fraction of hydrofluoric acid is higher than 2%. With the increase of hydrofluoric acid concentration, the corrosion controlling step changes from electrochemical reaction to mixed mass transportation-electrochemical reaction. EIS and the plots present the change of time contant from one to two, i.e. capacitance loop in high frequency and inductance loop in low frequency.

The microstructure of inhibition layer in galvanized coating on 440 MPa IF-HS Steel was studied by field emission environmental scanning electron microscope (FE-ESEM) and transmission electron microscope (TEM). The results showed that the inhibition layer is composed of two phases. The one is fine FeAl₃ phase, which exists as single layer on the steel substrate and underneath the coarse grains. And the another is coarse Fe₂Al₅, which exists on the surface of the inhibition layer. The growth mechanism of inhibition layer showed that FeAl₃ phase is the first forms preferentially on the steel substrate, and Fe₂Al₅ grows is through the consumption of FeAl₃ phase.

According to the typically tropical marine atmospheric corrosion features in Xisha area, a laboratory-accelerated corrosion method was developed on the base of the equivalent calculation. The correlation between atmosphere exposure in the tropical marine and the accelerated corrosion was studied from the dynamic characteristics, mechanism of corrosion, corrosion products. The results showed that, to some extent, the uv/cycle wet-dry synergistic accelerated corrosion test can simulate the corrosion behavior of 304 stainless steel in the tropical marine atmosphere, which can be predicted by the synergistic accelerated corrosion test.

The corrosion behavior of the Q235 carbon steel in Beijing soil environment was investigated by burying test in nature field for one year, two years and two point five years, electrochemical impedance spectroscopy(EIS) test, morphology observations, and weight-loss method. The results showed that the general corrosion occurred mainly on the Q235 carbon steel in Beijing soil, but the serious pitting corrosion was observed locally. With the increase of burying time, the average depth of pitting and the deepest depth of pitting both increased, while the corrosion rate increased first and then decreased. The corrosion product of the Q235 carbon steel mainly consisted of α-FeOOH, β-FeOOH, γ-FeOOH, and γ-Fe₂O₃. With the increase of burying time, the content of α-FeOOH increased, meanwhile the compactness and continuity of the corrosion product layer improved, but it could not protect the substrate.

The corrosion behavior of high-strength low-alloy steel in natural seawater without and with 0.01 mol/L H₂O₂ was investigated by electrochemical polarization, Raman spectroscopy, X-ray diffraction (XRD) and rotating ring-disk electrode (RDE) experiment. The corrosion mechanism of the steel in each solution was discussed. The results showed that the free corrosion potential and limited diffusion current density of the steel increased obviously due to the addition of H₂O₂ in seawater, meanwhile the hydrogen-evolution potential also shifted negatively. The phase constituents of the rust layer in two solutions were almost the same, and the oxygen reduction process of the steel in two solutions was controlled by the two-electronic reaction. In conclusion, the addition of H₂O₂ could efficiently accelerate the corrosion rate of the steel in natural seawater, but could not change its corrosion mechanism.

The corrosion morphology of the Q235 steel in simulated atmospheric environment was obtained using the established image acquisition system. In order to gain the detailed information of the images, wavelet packet-based image analysis method was applied to decompose the improved images and energies of sub-images (according to the Shannon entropy standard to choose the optimal sub-images with high regularity) were extracted as characteristic information. The results showed that the corrosion extent of the Q235 steel specimens was qualitatively analyzed which correlated well with the change of the energies of sub-images. The relationship between the characteristic information and corrosion mass loss of the samples was evaluated by regression analysis. Using the equation given by the regression analysis, the corrosion degree of the Q235 steel specimens could be quantitatively analyzed.

The effect of urea (0.1%, mass fraction) on corrosion of Q235 steel in soil with humidity of 30% was investigated by electrochemical impendence spectroscopy (EIS) and polarization curve. At the initial experiment period, urea was adsorbed on the surface of carbon steel, and one time constant with an inductive reactance arc appeared in the EIS. Along with the time, urea was decomposed into ammonia, hence pH decreased. The potential of carbon steel increased and its corrosion rate decreased over experiment time. Warburg impedance was found at the later stage, which indicated that the process was controlled by concentration polarization.

A new pyridine derivative, 2-((pyridine-2-ylimino)methyl)phenol (PMP) was synthesized and its inhibition effect in 1 mol/L HCl for Q235 steel was studied by means of mass loss measurement, potentiodynamic polarization and electrochemical impedance spectroscopy. Generally, the results indicate that PMP has excellent inhibiting effect. The inhibition efficiency increases with the increase of inhibitor concentration in 1mol/L HCl and the inhibition efficiency is up to 87.9% at the concentration of 15.0 mmol/L. The electrochemical measurements show that PMP acts as a mixed type inhibitor with cathodic inhibition as dominative action. The adsorption of PMP on the Q235 steel surface obeys the Langmuir adsorption law and contains both physisorption and chemisorption.

The synergistic inhibition effect between oleic-based imidazoline quaternary ammonium salt (OIMQ) and thiourea (TU) for Q235 carbon steel in CO₂-saturated brine solution was investigated by using polarization curves and electrochemical impedance spectroscopy (EIS). The results showed that TU had strong inhibition on the anodic and cathodic processes of carbon steel corrosion, while OIMQ acted as mixed-type inhibitor preferentially restraining the anodic process of metal. The combination of OIMQ and TU could effectively decrease the additive concentration and showed excellent synergistic inhibition effect. A bi-layer inhibitor film with the inner layer of TU molecules and the outer layer of imidazoline molecules was formed, which could retard the desorption of TU molecules and the attack of aggressive ions.

The all-solid-state Ag/AgCl reference electrode was prepared by thermal-dip coating and electrochemical reduction method. Effects of chloride ion concentration, temperature, light, pH and seawater flow on the potential of the Ag/AgCl reference electrode were studied in this paper. The results showed that the as-prepared Ag/AgCl reference electrode had good Nernst response and temperature response characteristic. If dissolved oxygen existed in the solution, on the electrode surface Ag₂O formed under sunshine and the electrode potential drifted. The flow rate of seawater had great effect on the electrode potential, however，the influence of pH value was minimal.

Microarc oxidation (MAO) coatings were obtained on the AZ91D magnesium alloy by AC pulse electrical source in a silicate-aluminate based composite electrolyte containing various concentrations of C₃H₈O₃. The morphologies and thickness of ceramic coatings were characterized by SEM and layer thickness meter, respectively. The corrosion resistance of coatings in a 3.5%NaCl neutral solution was evaluated by the immersion test and electrochemical impedance spectroscopy (EIS). The results showed that the striking voltage and final voltage increased gradually with the increase of C₃H₈O₃ concentration during the MAO process. With the increase of C₃H₈O₃ concentration in the electrolyte, the corrosion resistance of the coatings increased at first and then decreased gradually, however, the variation of the coating thickness was not obvious. The EIS results showed that the corrosion resistance of the coatings was influenced by the inner dense layer. The coating exhibited better corrosion resistance in the electrolyte containing 5 mL/L C₃H₈O₃ due to its relatively compact microstructure.

Abstrat: The electrochemical behavior of AZ31 alloy in Mg(ClO₄)₂ solution with different additives was investigated by polarization curve, electrochemical impedance, constant current discharge and immersion corrosion tests. The results showed that the addition of NaF makes the open circuit potential and activation potential more negative, decreases the corrosion current in the polarization curve and corrosion rate in immersion test, increases the discharge efficiency, and especially shortens discharge hysteresis time. In contrast, the addition of La（CH₃COO）₃ increases the discharge efficiency, but has no beneficial effect on the discharge hysteresis and corrosion resistance of the alloy.

Abstract：In order to solve the galvanic corrosion problem between bronze and silver, the self-assemble monolayers(SAMs) of odtadecanrthiol (ODT) was prepared on the surfaces of bronze and silver. The galvanic corrosion between bronze and silver were investigated by couple corrosion current and accelerated discoloration test. Corrosion inhibition and function mechanism of ODT SAMs were investigated by X-ray photoelectron spectroscopy (XPS), polarization curves and differential capacity methods. The results showed that ODT molecular adsorbed on the surface of bronze and silver to form SAMs through the formation of thiolate. In a solution of 3.5%NaCl concentration and sulfur air, the ODT SAMs could prohibit the galvanic corrosion between bronze and silver. ODT SAMs was a kind of mixed inhibitors.

Adopt accelerate circulation corrosion test methods which include impact test, salt spray test, ultraviolet illumination test and humid heat test to analysis the characteristics of electrochemical impedance spectroscopy (EIS) on different accelerate circulation time. The EIS of coating increased in the middle and late stages, and new time constants took place, which could be related to resolving of the chemical conversion film and corrosion of the aluminum on the activation zone. The water absorbing capacity of coating were calculated and found increasing at first and then decreasing with increasing of accelerated circulation time, the water absorption rate finally stabilized at about 5%.