Effect of grain size on oxidation of 18Cr-8Ni heat-resistant steels in high temperature water steam was studied at 700 ℃. Oxidation kinetics was obtained by weighting specimens at intervals. After oxidation, all the samples were investigated using field emission scanning electron microscopy (FE-SEM) in terms of plain and cross section views, the chemical composition was analyzed by X-ray energy dispersive analysis (EDS), and the oxide phases were identified by X-ray diffraction (XRD). The results show that grain refinement improves the oxidation resistance of steels to high temperature water steam by lowering the mass gains and postponing the onset of breakaway oxidation; grain refinement alters the microstructure of oxide scale by reducing the size of “crater” oxide region and promoting the formation of Cr-rich layer at scale/alloy interface; the beneficial effects of grain size on oxidation of steels are ascribed to the promotion of oxide nucleation and Cr transport towards scale/alloy interface.

The transport behavior of sodium ions along a fusion-bonded epoxy coating-steel interface was investigated in 0.6 mol/L NaCl solution (60 ℃) by ion selective microelectrode. Based on Fick's second law a mathematical model was established. The results showed that experimental results was coincided with mathematical model well. The calculated apparent diffusion coefficient of Na⁺ by model had similar order of magnitude with previously reported values.

The hydrogen permeation characteristics of Q235 steel under different applied cathodic protection potential in 3.5%NaCl solution were investigated by using electrochemical, tensile and micro-hardness test. The fracture morphology was observed by scanning electron microscopy (SEM). When the cathodic potential shifted to the negative direction, there was no correlation between maximal tensile strength, yield strength, and hydrogen embrittlement, but the reduction of area decreased. When the polarization potential was -1100 mV, the micro-hardness increased significantly and the fracture morphology exhibited brittle fracture feature.

Abstract：The influence of applied tensile stress on the pitting electrochemical behavior of X80 pipeline steel in NaHCO₃ + NaCl solution was investigated by using electrochemical noise measurement combining with potentiodynamic polarization measurement. The results showed that the pitting of X80 pipeline steel was inhibited when the applied tensile stress lower than 100 MPa, and the lower the stress was, the weaker the inhibition was. The pitting of X80 pipeline steel was promoted when applied tensile stress higher than 200 MPa, and the higher the stress was, the stronger the promotion role was.

To elucidate the effect of Cr on the corrosion behavior of cast X52 steel in H₂S containing environments, potentiodynamic polarization tests, electrochemical impedance spectroscopy (EIS) measurements, immersion tests SEM and EDS analysis were conducted. The results show that Cr addition leads to a remarkable decrease in the cathodic current density. However, the corrosion resistant did not increase linearly with the increasing Cr content. The addition of Cr altered the corrosion morphology, whilst the formed oxide scale transformed gradually from porous to compact. SEM-EDS analysis revealed the presence of Cr-rich corrosion products in the inner portion of the formed oxide scale, which may be responsible to the distinct drop in corrosion rate.

The general corrosion behavior of 304L grade stainless steel in simulated pressurized water reactor (PWR) primary loop was studied using still autoclave, the corrosion test lasted for 1680 h. The corrosion oxide films were analyzed macroscopically and microscopically. The general corrosion and general corrosion rate of 304L stainless steel was quantitatively valued. Results showed that the oxide film was formed on the surface of 304L in 336 h. Oxide films were two sub-layers structure, the diameter of oxide particles near the metal substrate ranged from 50 to 100 nm, polygonal bigger oxide particles with diameter ranging from 0.5 to 1.6 μm were distributed on the small particles. After 1680 h experiment of high temperature and high pressure, the diameter of small particles near the metal substrate grew up to 80 to 250 nm, the bigger oxide particles grew up to 0.8~2.5 μm. The compact and small particle oxide film was very corrosion resistant. The weight gain rate of samples declined very much firstly, and then changed little. After 1680 h corrosion test, the general corrosion rate declined to only 2.85×10^-3 mg/(dm²h).

A lab experimental platform was built to investigate the effect of the AC stray current on the corrosion of buried pipeline. The mathematical model which involved the AC current density, the damage area, soil resistivity, the interference voltage and the coating resistivity was established. The AC current density which would improve efficiency could be obtained indirectly from the model. By using CDEGS software, the distribution law of the parallel length, current rate, distance, soil resistivity and other aspects of AC interference along the pipeline was studied. The results showed that the damaged area, AC interference voltage, soil resistivity and coating resistivity had a significant impact on the AC stray current density. That is, the AC corrosion was small when the current density was lower than 3 mA/cm²; it showed a stronger effect when the current density was between 3 and 10 mA/cm², and it corroded very heavily when the current density was higher than 10 mA/cm².

The galvanic corrosion behaviors of AZ91D magnesium alloy coupled with aluminum alloy, zinc alloy, Q235 carbon steel and copper were investigated in tap water and 3.5%NaCl solution. The effects of corrosion environment, coupled material and cathode to anode area ratio (CAAR) were discussed. During the corrosion process, pH of the electrolyte was measured and the galvanic currents of all couples were recorded. Meanwhile, the corrosion rate of AZ91D magnesium alloy was calculated by mass loss method, the corrosion morphologies of AZ91D were observed by SEM and the corrosion products were analyzed by XRD. The results showed that the pH of the electrolyte increased due to the galvanic corrosion of AZ91D magnesium alloy, the main corrosion product was Mg(OH)₂, and the addition of NaCl would accelerated the galvanic corrosion rate of AZ91D magnesium alloy. Coupled materials with low hydrogen overpotential would promote the galvanic corrosion of AZ91D magnesium more seriously than that with middle hydrogen overpotential, the polarization property of coupled materials also had an obvious effect on galvanic corrosion of AZ91D magnesium alloy. Moreover, larger CAAR would result in faster galvanic corrosion, and the galvanic current of AZ91D magnesium alloy increased linearly with the increase of CAAR.

The corrosion behavior of pure copper in Beijing soil environment was investigated by burying test in nature field for 1, 2 and 2.5 a, electrochemical impedance spectroscopy(EIS), macro-morphology, SEM, XRD and weight-loss method. The results showed that nonuniform general corrosion occurred mainly on the pure copper in Beijing soil, with the slight corrosion. The corrosion rate of pure copper nearly decreased linearly with the increase of burying time, while the defects in island-like corrosion product reduced, and the compactness of the corrosion product improved. The corrosion products mainly consisted of Cu₂(CO₃)(OH)₂, CuO3H₂O and CuCl.

Abstract：Liquid microcapsule was prepared by using the phase separation method. Polyvinyl alcohol (PVA) and methyl silicone oil were used as the shell and core materials of microcapsule, respectively, and then co-deposition was executed through a graded current density on the surface of Fe substrate. The field emission scanning electron microscope (FE-SEM), contact angle of distilled water and potentiodynamic polarization were applied to characterize the micro-morphology, wettability and corrosion resistance between two different electroplatings. The experimental results showed that the liquid microcapsule was incorporated into the co-deposition films, and it led to the change of contact angle from 90° to 131°. The co-deposition film exhibited better corrosion resistance than ordinary Cu coating and its corrosion current density decreased by three orders of magnitude in 1% (mass fraction) H₂SO₄ solution. The corrosion potential shifted positively from -0.63 to -0.27 V.

The influences of pulse electroplating parameters on deposition rate, internal stress, porosity and microstructure of high speed nickel coating were studied. The results showed that the temperature, average current density, frequency, reverse pulse coefficient and duty cycle had great impact on the microstructure of coatings. Compared with the conventional method of electrodeposition of nickel, high speed pulse electrodeposition of nickel had the advantages of high efficiency, energy saving and so on.

The optimal scheme for synthesis of heptadeceny imidazoline with high productivity and inhibition efficiency was determined by orthogonal test. The structure of heptadeceny imidazoline was characterized by FTIR and MS-ESI. The inhibition performance of heptadeceny imidazoline on Q235 steel in HCl solution was investigated by mass loss method in the various conditions with different HCl concentration, temperature and dipping time. The result showed that the organic compound had good inhibition for Q235 steel in 1 mol/L HCl solution.

The corrosion behavior of reinforced steel with different surface states in simulated pore solution with gradual augment of Cl^- was investigated by using electrochemical measurements, scanning electron microscopy with energy dispersive SEM/EDS and XRD. The variation of corrosion potential and corrosion current density of the reinforced steel with corrosion time was obtained, and the morphology and structure of corrosion products formed on the sample were analyzed. The results showed that the reinforced steel with different surfaces state had different corrosion characterizations; the corrosion process of reinforced steel might include three steps, i.e., the formation of passive film, the aggression of Cl^- and the calcium deposition. It is more easy to happen corrosion for reinforced steel with oxide layer.

In order to reveal the influence of the defects size on the load capacity of a corroded line pipe of X65 steel, the distribution of the von Mises stress and strain as well as the relation of the residual strength of the line pipe with the depth and diameter of the flat bottom defects were analyzed by the finite element methods (FEM), meanwhile, the lab experiment was carried out to verify the calculated results. The results showed that, the deeper of the corroded defects, as well as the bigger the diameter of the defects, the less residual strength was, and the depth exhibited much significant influence than the diameter. Tensile tests were carried out for the specimens with flat bottom defects of 6 mm in diameter and of 0.25t （t, thickness）and 0.5t in depth respectively, it follows that the experimental results were coincident to those of calculated by FEM, especially that of the specimen with the bigger defect depth.

The stress corrosion cracking (SCC) of the LD10 alloy with pro-cracked double cantilever beam (DCB) in 3.5%NaCl, N₂O₄, unsymmetric dimethyl hydrazine (UDMH) and H₂O solutions was investigated by the method of stress corrosion tests. The crack growth rate and the threshold stress intensity factors were obtained. The fracture surface of the samples was observed by SEM. The results showed that the corrosion of the LD10 alloy was the most serious in 3.5%NaCl solution, secondary in N₂O₄ solution, and the lightest in UDMH and H₂O solution.