The effect of negative pulse width of asymmetric bipolar pulse on the compactness of plasma electrolytic oxidation (PEO) coating on Mg-Gd-Y alloy is not yet revealed nowadays. Here, PEO coatings on Mg-Gd-Y alloy were prepared by means of bipolar pulse whose negative pulse width was changed within a desired range. The microstructure and corrosion performance of the coatings were examined by scanning electron microscope (SEM) and electrochemical measurements respectively. The results show that negative pulse width plays an important role on compactness of PEO coatings; and with negative pulse width within a suitable range the compactness of coatings can be surely enhanced，as a sequence, the corrosion resistance of the coatings is evidently increased.

The effect of saturated CO₂ on corrosion behavior of 13Cr pipe steel in high concentration chloride environment was studied by EIS, polarization test, EN test and SEM. The results indicated that the corrosion rate and corrosion probability of 13Cr pipe steel were accelerated in high chloride environment with the presence of saturated CO₂. The 13Cr pipe steel suffered from pitting corrosion in high chloride concentration environment, whilst, from uniform corrosion by the synergistic effect of Cl and CO₂. The stability of the passive film of 13Cr pipe steel decreased in high concentration chloride environment with saturated CO₂, which can be explained by the dehydroxylation of the outer part of the passive film by carbonic acid and the increase of ionic conductivity of the passive film in aqueous electrolytes.

The pitting behavior of HP2-13Cr in a simulated high pressure and high temperature gas well environment (including three pericds: acidizing→returned residual acid→ produced water) was investigated by OM/SEM observation. The results showed that the pitting was mainly occurred in the returned residual acid; the statistical analysis of the depth distribution of pits showed that the pitting rate in the period of returned residual acid was 7.56 mm/a，while 0.47 mm/a in the produced water. The depth distribution of pits followed Gumbel model and the shape of pits was shallow.

There are many large oil tanks constructed in coastal area for its good natural conditions. During hydraulic inspection of which, seawater is often employed for saving cost. The paper investigated the corrosion performance of 12MnNiVR steel in seawaters aiming to simulate the corrosion occurred on the bottom, wall and roof of the oil tank. A comparison study was performed to investigate the effectiveness of sacrificial anode for the steel. The corrosion morphology and products were examined by SEM and XRD techniques. The results show that corrosion rate of the tank bottom is greater than that of the tank roof. The corrosion rate of 12MnNiVR steel decreases obviously when the protection with sacrificial anode is applied to the test specimens, i.e. only a slight uniform corrosion occurs for the specimens on the bottom, roof and wall of the tank; the corrosion product is compact and there is no obvious corrosion pits on the surface; in that case the corrosion degree is within the allowable range of the design specification. In the case of no cathodic protection, the metal surface becocmes rough with porous corrosion product, presenting the feature of local corrosion.

Multilayered Ni coatings were prepared by ultrasound-assisted electrodeposition on Q235 steel substrate. Corrosion weight loss and electrochemical method, as well as XRD and SEM were employed to comparatively examined the corrosion performance of the multilayered Ni coating with the ordinary Ni coating. The results show that for the multilayered Ni coating, in 20 vol% HNO₃ solution the corrosion rate was lower obviously; in 3.5 mass% NaCl solution the corrosion potential was higher dramatically, and the corrosion current was one order of magnitude smaller than that for the ordinary electrodeposited Ni coating. XRD analysis results show that multilayered Ni coating exhibits a preferential (111) orientation with much uniform appearance and finer gain size rather than the ordinary Ni coating. Furthermore, the preferential orientation of grains of the ultrasonic Ni layer is quite different to that of the ordinary Ni layer, which, thereby, may be beneficial to destroy the growing path of the pinhole-like defects so that to enhance the corrosion resistance of the multilayered Ni coatings.

In order to study the corrosion protection measures for carbon steel corroded in the atmosphere polluted by heavy industries, the snow water collected from northern city—Fushun Wanghua area was used as the corrosion medium, and 3.5%NaCl as a comparative ones. The corrosion resistance of 20 steel without and with Ni-Cu-P electroless coating as well as the inhibition effect of CeCl₃ for the steel in the snow water were investigated by means of polarization curves EIS and immersion methods. The result showed that the corrosivity of snow water was close to 3.5%NaCl solution; the Ni-Cu-P coating could form a compact passive film; and the CeCl₃ addition in snow water could facilitate a film deposition on 20 steel surface. The passive film and deposited film not only act as a barrier for oxygen migration, but also protect the steel from direct contacting with snow water, which leading to a lower corrosion current density and a higher charge transfer resistance, so, the corrosion rate of 20 steel in snow water was reduced. Thus, both the Ni-Cu-P electroless coating and CeCl₃ may be considered as protective coating or inhibitor respectively for carbon steel in seriously polluted atmosphere environment.

Polyaniline (PANI) was prepared by direct mixed oxidation in two inorganic acids (perchloric acid and hydrochloric acid). Structural characteristics and morphology of PANI products were characterized by fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) respectively. Then composite coatings of epoxy resin with PANI were prepared on Q235 steel substrate. The corrosion performance of Q235 steel with different composite coatings in 3.5 mass% sodium chloride (NaCl) aqueous solution were studied by electrochemical impendance spectroscopy (EIS) technique and Tafel polarization measurement. The results indicated that the presence of PANI could enhance the anticorrosive performance of the modified epoxy coatings in the contrast to pure epoxy coating, and the epoxy coating modified with the perchloric acid doped PANI exihibited the best performance of corrosion protection among the four modified coatings.

The main physicochemical properties of the soil at Chuanying District of Jilin City was examined according to the Code for Inyestigation of Geotechnical Engineering (GB50021-94) and test method of national soil corrosion test network. Then the main influence factors on the soil corrosion of the grounding grid were analyzed. The results showed that the soil resistivity was merely decreased from 53.2 Ω·m to 25.1 Ω·m when the moisture content was increased from 17.14 % to 21.21%. However, the soil resistivity was drastically increased from 234.6 Ω·m to 2253.5 Ω·m when the moisture content decreased from 11.25% to 2.04%. When the pH of soil was lower than 7.0, the maximum corrosion rate of the Q235 steel electrode was 0.6773 mm/a and the corrosion current density was 59.37 μA·cm^-2, respectively. The minimum corrosion rate of electrode was 0.2328 mm/a and the corrosion current density was 23.01 μA·cm^-2, respectively, when the soil pH was 7.0~8.5. The maximum corrosion current density was 98.76 μA·cm^-2 and the Q235 steel electrode corrosion was the most serious when the Cl^- concentration of soil was about 1.0 mass%. However, when the Cl^- concentration of soil was increased to 4.0 mass%, the electrode corrosion was weakened with corrosion current density of 29.40 μA·cm^-2 .

Cinnamaldehyde, hypnone and primary amine were used as raw materials to synthesize a novel mannish corrosion inhibitor MR-1. MR-1 was well characterized by IR spectrum. Besides, a comprehensive evaluation on corrosion inhibition effect of MR-1 was carried out through electrochemical mass loss measuremants. The results showed that MR-1 was a mixed type inhibitors, and the absorption of the inhibitor molecules on the surface of mild P110 steel formed protective film, which could be ascribed to “geometrical covering effect”. Mass loss results suggested that MR-1 had an excellent corrosion inhibition effect for P110 steel in HCl solution, which, thereby, could be ranked as a first class product corresponding to the oil industry standard SY/T5405-1996. In the presence of the inhibitor MR-1, the corrosion of the P110 steel was gradually accelerated with the increasing concentration of HCl and temperature simultaneously, the higher concentration of the inhibitor could significantly enhance the inhibition efficiency. Furthermore, the relationship between the corrosion inhibition effect and the inhibitor concentrations elucidated that the adsorption of the mannish inhibitor on the steel surface in an acidic solution conformed with the Langmuir adsorption isotherm equation.

The influence of thiourea(TU) addition on the deposition rate and quality of coating was investigated for a low temperature alkaline electroless nickel plating process. The results show that the deposition rate firstly decreases and then increases with the increasing thiourea addition, while the suitable addition amount is 1 mg/L. Due to the thiourea addition, the grains of the coating are refined, and the coating becomes smooth and even, which may be ascribed to the inhibition of TU to the reduction of H⁺. Thiourea has little influence on coating chemical composition. XRD results show that the coating consists of dominant Ni and a little Ni₅P₄. A small amount of thiourea may promote polarization, resulting in decline of plating rate, whereas depolarization occurs with the increasing addition, resulting in the rise of plating rate.

A new Multi-amide of Gemini inhibitor (OPDO) was synthesized and its inhibition effect on Q235 carbon steel corrosion in hydrochloric acid solution was evaluated by weight-loss method and electrochemical polarization measurements. The results showed that OPDO is effective in reducing corrosion of carbon steel in hydrochloric acid solution, which belongs mixed-type inhibitors and its maximum inhibition efficiency can reach to 99%. The adsorption of OPDO on the carbon steel surface obeys Langmuir's adsorption isotherm. The thermodynamic parameters of adsorption revealed a strong interaction between the inhibitor and the surface of the corroding carbon steel. The influence of the inhibitor concentration, the solution temperature, and the acid concentration on the corrosion of carbon steel have also been investigated.

Sub-rapidly solidified Cu-15Al-4Fe alloy bar was prepared by copper mould casting. The microstructure, composition distribution, phase constituent and corrosion resistance were investigated using optical microscopy, scanning electron microscopy, energy dispersive spectrometer, X-ray diffraction, static immersion and electrochemical experiment. The results showed that the sub-rapidly solidified Cu-15Al-4Fe alloy present columnar structure composed of +(+). Cu-15Al-4Fe alloy suffers from dealuminization and deferrization corrosion in 3.5%NaCl and 5.0%H₂SO₄ solution, However, the alloy exhibits a higher corrosion resistance in 3.5%NaCl solution due to evident passivation phenomenon rather than in 5.0%H₂SO₄ solution.

Potentiodynamic polarization, electrochemical impedance spectroscopy and capacitance measurements were used to reveal the passivation behavior and electrochemical characterization of the passive film formed in a buffer solution 0.5 mol/L Na₂CO₃+1 mol/L NaHCO₃ on P110 oil tube steel by different potentials. It is indicated that P110 steel exhibits an obvious passivation behavior in a potential range from -200 mV to 800 mV. EIS result shows that with increase of film formation potentials, the passive film is much denser, stable with better corrosion resistance. Mott-Schottky figure demonstrates that an n-type semi-conductive property of the passive film which formed on P110 oil tube steel in 0.5 mol/L Na₂CO₃+1 mol/L NaHCO₃ buffer solution. With increasing the film formation potential, the donor density of the passive film increased, therwith the protectiveness of the film enhanced.

In micro-arc oxidation technology, energy consumption plays an important role. In this paper, the influence of solution concentration, current density and time on energy consumption for micro-arc oxidation of aluminum plate with bigger surface area was investigated. The results show that: in order to get the same ceramic coating thickness, the solution concentration of the electrolyte for bigger area samples should be 4~5 times higher than that for the small ones; with the increase of current density, the energy consumption is increased; as oxidation time extending, the thickness of ceramic coatings is increased, whilst, the energy consumption is decreased for the case of larger area samples.