Since the gap between the probe electrode and the substrate electrode of scanning electrochemical microscopy (SECM) is not easy to control and clear, based on the feedback model and the COMSOL numeric simulation, the effect of the moving distance of the step motor on the real distance is investigated. The effects of the oxidation film of aluminum alloy on the approaching curve and the test error of the distance on the kinetic parameters of electrochemical-chemical reaction are also investigated. The results show that the positive and negative feedback effect is related to the gap between the probe and the substrate electrode. The smaller the gap, the stronger the feedback effect, while the feedback effect is also impacted by the regeneration kinetics on the substrate electrode. The ratio of the step motor-controlled distance to the approaching and withdrawing distance from the substrate electrode to the actual moving distance of the tip is 0.843 and 0.568, respectively, which indicates when the stepper motor movement is labeled 1 μm, the actually distances are only 0.843 and 0.568 μm. The state of the oxide film on the surface of aluminum alloy affects the approaching curve from partial positive feedback to pure negative feedback, and the distance error of stepper motor movement leads to the error of chemical homogeneous reaction rate constant in EC reaction as high as 60%. Precise gap control is the fundamental for scanning electrochemical microscopy experiments.

The corrosion behavior of 907 steel, as hull structural material, in seawater with mono-, and di-cultures of Desulfovibrio sp. (belonging to sulphate-reducing bacteria) and Vibrio alginolyticus was studied by means of weight loss- and electrochemical-method, as well as surface analysis methods. The results demonstrated that the corrosion rate of the steel in seawaters can be ranked increasingly as the following: Desulfovibrio sp.+Vibrio alginolyticus<Vibrio alginolyticusDesulfovibrio sp. The metabolism of Desulfovibrio sp. was inhibited due to the lack of nutrient substances and the presence of oxygen, and the corrosion rate of 907 steel in the seawater with Desulfovibrio sp. was the same as that in sterile seawater. However, Vibrio alginolyticus metabilited well in the test condition, and the presence of Vibrio alginolyticus may inhibit the corrosion of 907 steel due to that the oxygen was removed by metalism of Vibrio alginolyticus. The corrosion of 907 steel was further inhibited in the presence of mixed Desulfovibrio sp. and Vibrio alginolyticus, which may facilitate the formation of compact biofilm on the surface of 907 steel.

Salt spray test and immersion test for two accelerated weathering tests were carried out to research the effects of nano-CeO₂ as a pigment to the corrosion resistance of polyurethane coating. According to EIS, ATR-FTIR, SEM and AFM characterized and analyzed the performance and micromorphology change of coating. The results show that as a pigment nano-CeO₂ could decrease the rate of resistance reduction of polyurethane coating. When the concentration of adding nano-CeO₂ was less than 0.5%(mass fraction), the EIS impedance spectrum dropped rapidly with acceleration time elapsed due to the electrolyte and H₂O penetration into coating quickly and nano-CeO₂ hydrolysis. While the corrosion resistance get markedly changed and maintained high impedance for a long time of the coating with additive 1.0% nano-CeO₂. This phenomenon may be due to CeO₂ hydrolysis in coating micro crack, reduced the pore channel, and Ce(III, IV) migrated to the Al alloy/coating interface, inhibiting the corrosion of active site, thus decreasing the attenuation process of impedance. At the later stage of salt spray test, CeO₂ further hydrolysis leaded to Ce ions dissolution erosion, which caused micro cracks expansion again and coating impedance reducing quickly. When the addition of nano-CeO₂ excessed 1.0% would weaken the adhesion of coating on aluminum alloy matrix. Long time immersion test showed that 1.0% of nano-CeO₂ could achieve balance of Ce ions dissolution and migration, and increased the anticorrosion performance of PU coating.

Three different oxide scales on the surface of bronze QSn7-0.2 electrodes were prepared in Li-Na-K eutectic molten carbonates at 450°C via potentiodynamic polarization, potentiostatic polarization by 0.2 V and simple immersion by open circuit potential respectively, then were characterized by means of optical microscopy and X-ray diffractometer (XRD). While the feasibility of which as potential inert anode for electrochemical transformation of CO₂ was assessed in the melt by electrochemical method. The result shows that besides Cu₂O and CuO, SnO₂ is detected in the oxide scales of the bronze QSn7-0.2 electrodes oxidized via potentiostatic polarization by 0.2 V and simple immersion by open circuit potential. The oxide scales with SnO₂ can significantly prevent the bronze QSn7-0.2 anodes from corrosion and act also as electro-catalyzer for the oxygen evolution.

Polyaniline (PANi) was in situ deposited on the surface of modified graphite (MGE) via different electrochemical methods to prepare composites of PANi/MGE. Their morphology and microstructure were examined by scanning electron microscopy (SEM) and the Fourier transform infrared spectroscopy (FT-IR). While their anticorrosion properties were assessed by corrosion potential measurement and electrochemical impedance spectrometry. Experimental results showed that MGE as a support material can provide sufficient reaction sites for the deposition of aniline to form the film-like composites of PANI/MGE. There exists strong interaction at the interface of PANI and MGE. Test results of anticorrosion performance illustrated that among others, the composite of PANI/MGE prepared by polymerization with constant current step technique showed the best corrosion resistance and the highest open circuit potential.

The hybrid silane sol was prepared by adding silane coupling agent in the hydrolyzing tetraethyl orthosilicate (TEOS), and then the organic-inorganic hybrid silane-coating was successfully prepared on the AZ31 Mg-alloy using a simple dip-coating method. The morphology and composition of the hybrid coating were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersion spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). Moreover, the corrosion resistance of the hybrid silane-coating was studied by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that the Mg-alloy substrate was completely covered with organic-inorganic hybrid silane-coating, which was uniform and compact. The resistance of the hybrid silane-coating (1.717×10⁴ Ωcm²) is higher than that of the conventional chromate conversion coating (1.611×10⁴ Ωcm²), and correspondingly, the corrosion current density of the AZ31 alloy with coating is about 2 orders of magnitude lower than that of the bare alloy. The steric effect of the silane coupling agent can effectively adjust the traditional hydrolysis polycondensation process of TEOS and prevent the hybrid silane sol from further clustering. The as-prepared coating is compact and uniform, which can resist the corrosive medium and provide excellent protection for Mg-alloy.

The corrosion behavior of Q235 steel beneath electrolyte thin films of 0.01 mol/L NaCl solution was conducted to simulate marine atmospheric corrosion by simultaneous electrochemical measurements and acquisition of corrosion images. The results show that atmospheric corrosion of Q235 steel initiates around pearlites and presents the character of local corrosion which developed to become uniform corrosion afterwards. According to the result of wire beam electrode (WBE) measurement, the mean corrosion potential and the corrosion potential standard deviation decreased, and the anode area enlarged with the exposure time. Analysis of the neural network shows that the content of α-FeOOH in rust layers increased with exposure time, which blocked the process of oxygen diffusion, resulting in the transformation of corrosion mode from local ones to uniform ones. In conclusion, when the electrochemical information shows that the corrosion tends to transform from the local ones to the uniform ones, correspondingly the image information also shows that a protective rust gradually formed with the increasing exposure time. Therefore, the corrosion behavior of Q235 steel presents well correlation with the feature of image information.

The effect of a direct current (DC) electric field on the corrosion of Zn exposed in a simulated industrial environment for a period of 30 d was studied by using weight loss and electrochemical tests, XRD and SEM techniques. The results show that the corrosion rate of Zn increased with the increase of DC electric field intensity. With an applied DC electric field, the cathodic reduction process and the anodic dissolution reaction process of Zn in the simulated industrial environment can be accelerated. The influence of the DC electric field on the corrosion behavior of Zn can be attributed to that the distribution of ions in the solution may be altered by the electric field, thus, it can change the reaction site of the formation and also the structure of the corrosion product. Then, the corrosion rate of Zn in the simulated industrial environment can be increased.

The atmosphere corrosion behaviour of transmission tower materials including Q235, Q345 and galvanized steel in simulated industrial environments of spraying NaHSO₃ solutions was investigated by means of mass loss method, XRD analysis and SEM observation. The results indicated that the corrosion degree of Q235 and Q345 was not significantly increased with the increase of NaHSO₃ concentration of the simulated solution below 0.005 mol/L, and that the above two steels presented a trend of accelerated corrosion with the increase of NaHSO₃ concentration in the range between 0.005 and 0.02 mol/L, and that the corrosion degree of Q235 and Q345 had not obvious changes with the increase of NaHSO₃ concentration in the range between 0.02 and 0.03 mol/L. The results of XRD analysis and SEM observation further suggested that the above corrosion phenomena of Q235 and Q345 steel are strongly related to the fact whether the conversion of corrosion product γ-FeOOH to α-FeOOH did occur or not for the media with the amount of NaHSO₃ in every individual concentration range. In addition, the corrosion products on galvanized steel mainly consisted of ZnO, Zn₄CO₃(OH)₆, Zn₅(CO₃)₂(OH)₆ and Zn₄SO₄(OH)₆ despite different concentration of spraying solutions.

The influence of soot on the corrosion behavior of 409 stainless steel for automotive muffler was studied by means of oxidation-immersion-evaporation cycle test with electrochemical impedance spectroscopy, XRD, SEM as well as pitting depth-and corrosion weight loss-measurement. The results show that the corrosion products formed on the sample surfaces are similar in the condensate liquids with and without soot. However, the corrosion potential increases lightly and both the pitting depth and weight loss become higher for the steel in the presence of soot. These can be attributed mainly to the galvanic effect between deposited soot and the stainless steel, which reduces the charge transfer resistance of the corrosion system and accelerates the corrosion of 409 stainless steel in the condensate solution.

A non-toxic and compound organic-inorganic corrosion inhibitor was prepared with cerium salt, polyphosphate, Zn-salt, borate and organic polymer as raw materials, and then the effect of which on the corrosion of alloy steel L921A in 3.5%(mass fraction) NaCl solution was studied by weight loss measurement in conjunction with orthogonal method. The results show that the corrosion inhibitor was an anodic corrosion inhibitor with inhibition efficiency 97% for alloy steel L921A. The electrochemical impedance spectroscopy (EIS) spectrum of the alloy steel L921A in 3.5%NaCl solution was composed of a high frequency capacitive loop and a low frequency inductive loop with two time-constants, indicating that the alloy steel L921A presented pitting susceptibility in 3.5%NaCl solution. When the corrosion inhibitor was added to the 3.5%NaCl solution, the EIS spectrum of the alloy steel L921A presented only a single capacitive loop with one time-constant. After immersion in 3.5%NaCl solution for 35 h, the electrochemical impedance of the steel increased from 10³ Ωcm² to 1.1×10⁴ Ωcm². In this case, the coverage of the corrosion inhibitor reached about 80% of the surface of the alloy steel L921A.