The galvanic corrosion behavior of continuous casting copper-clad steel- and electroplating copper-clad steel-bars with unclad two-end faces was investigated by galvaric corrosion test and a laboratory embedmant test in Dagang soil. Then macro- and micro-corrosion morphology was observed by optical microscopy and SEM. The results show that the degree of galvanic corrosion of the continuous casting copper-clad steel is more serious than the electroplating copper-clad steel. The surface morphology of the clad copper, the potential difference of the coupled samples and the surface area ratio of cathode to anode are the important factors responsible to the galvanic corrosion behavior. Especially the surface area ratio of cathode to anode can obviously influence the galvanic corrosion behavior. With the increase of surface area ratio of cathode to anode, the anodic corrosion rates increase.

Abstract：Influence of trace rare earth Ce addition on electrochemical corrosion behavior of X80 pipeline steel in Korla simulated solution were studied by EIS, SEM and XRD. The results showed that Ce can improve the corrosion resistance of X80 pipeline steel; Corrosion products are loose red-brown outer rust layer FeOOH and dense black inner rust layer Fe₃O₄; the inner part of the rust scale on X80Ce steel is more compact than that on X80 steel, thereby a better protectiveness for the substrate; At the same time, the low-frequency capacitive arc modulus value of X80Ce steel is larger than X80 steel.

By using a cantilever beam reversed bending and corrosion fatigue testing machine, the corrosion fatigue behavior of 25Cr2Ni4MoV steel in hydrochloric acid was investigated. The results showed that corrosion fatigue life decreased with the increasing cyclic stress and also the increasing concentration of hydrochloric. Besides, corrosion fatigue life is more vulnerable to magnitude of the cyclic stress than the concentration of the hydrochloric; the concentration of hydrochloric acid had less impact on the life within a certain concentration range. The failured samples were analyzed by using optical microscope (OM) and scanning electron microscope (SEM). The morphology showed that the fracture mechanism was intergranular cracking.

The situation of stress and strain was analyzed by Finite Element Analysis (FEA) for the corroded line pipe by deferent inner pressures and with single hemispheric corrosion defects, of which the radius and depth were set as t/8，t/4 and t/2 (t, the pipe wall thickness) respectively. Meanwhile, the residual strength of the pipes with corresponding defects were calculated respectively, as well as the empirical equation that relates to the residual strength and depth-thickness ratio d/t, was established, which shown that the residual strength decreased linearly with the increasing d/t.

Abstract：The accuracy of numerical calculation used to simulate a cathodic protection (CP) system was significantly influenced by the required boundary conditions of cathode and anode. At present, the effect of boundary conditions of cathode has been given more attention, while the effect of boundary conditions of anode is seldomly referred. The boundary conditions of anode in numerical simulation can be classified as constant current density, constant potential and real polarization curve. Errors caused by different boundary conditions of anode have not been reported and compared that gave rise to certain difficulties in numerical simulation. The effect of different boundary conditions of anode on numerical simulation in sacrificial anode cathodic protection (SACP) system and impressed current cathodic protection (ICCP) system has been studied with BEASY software based on boundary element method in this paper. The results showed that error between boundary conditions of sacrificial anode of constant open circuit potential and real polarization curve was not more than 1% in SACP system, and error between boundary conditions of auxiliary anode of constant current density and real polarization curve was less than 0.1% in ICCP system, which indicated that open circuit potential and constant current density could be selected as the boundary conditions of sacrificial anode and auxiliary anode respectively for the convenience of calculation in engineering applications.

The influence of α,α′-dipyridyl on electroless copper plating with sodium hypophosphite bath was investigated using SEM, XRD, Linear Polarization and AC impedance tests. The results show that the coating quality and stability of sodium hypophosphite bath are enhanced by proper amount of α,α′-dipyridyl, and the proper amount is 10 mg/L. The coating is uniform and compact under optimal conditions，the deposition is cubic crystalline pure copper. With the presence of α,α′-dipyridyl, the cathode peak current density decreases gradually to a stable value. The α,α′-dipyridyl inhibits the catalytic oxidation of hypophosphite, but enhances the dissolution of copper electrode resulting in suppression of the reduction of cupric ion, thus the coating quality may be inproved.

The corrosion test on BG90SS was carried out in the gas phase and liquid phase of H₂S/CO₂ containing environment respectively, in a high temperature and high pressured autoclave. The effect of different H₂S partial pressure on the corrosion behavior of BG90SS was discussed. The experimental results showed that the corrosion rate of BG90SS in the liquid phase was higher than that in the gas phase. XRD analysis showed that corrosion products consisted of Fe_xS_y and FeCO₃ in the liquid phase and the proportion of Sulfur-rich phase in the corrosion products increased with the increase of H₂S partial pressure. In the gas phase, the proportion of sulfur-rich phase also increased with the increase of H₂S partial pressure, however, FeCO₃ was not found in the corrosion products, indicating that the corrosion process in the gas phase was mainly induced by H₂S.

A new heteroercyclic compound, isonicotinaldehyde thiosemicarbazone (INT), has been synthesized. The inhibition efficiency for Q235 steel in 1 mol/L HCl solution was evaluated by means of mass loss, potentiodynamic polarization and electrochemical impedance spectroscopy. Then, the surface morphology was observed by scanning electron microscopy. It was found that INT exhibits excellent inhibition performance and the highest inhibition efficiency reaches 83.6% by 1.5 mmol/L. The adsorption of INT on Q235 steel followed the Langmuir adsorption isotherm and INT acted as a mixed type inhibition with cathodic inhibition as dominative action.

Abstract：New type ceramic-aluminizing coatings were prepared by pre-coated ceramic and followed by a cementation process, and thermal spraying an aluminum base coat plus a cramic coat and followed by a heat-tratment process respectively. Then the phase constituents of the coatings were characterized by XRD and their corrosion performance was also examined. The results show that the ceramic-aluminizing composite coating prepared by the later process has less porosity and better corrosion resistance to various corrosive media.

Two kinds of corrosion inhibitors were developed in order to solve the corrosion problem for 20^# carbon steel induced by TS-883 decalcifying agent. The corrosion behavior of 20^# carbon steel by TS-883 decalcifying agent solution with corrosion inhibitors, in comparison with imported similar decalcifying agents, was investigated using static immersion corrosion tests. The results indicate that the corrosion rate of 20^# carbon steel inTS-883 solution was 0.8139 mm/a, however by the same experimental conditions, the corrosion rate of 20^# carbon steel in TS-883 solution with the two corrosion inhibitors were 0.1628 mm/a and 0.1678 mm/a respectively, which was more or less the same as those with the imported agents.

A new high temperature and pressure autoclave and an auxiliary sample holder for SCC test under constant load were setup to simulate the high temperature and high pressured sour environment in oil fields. Experimental results indicate that tensile strength and yield strength of C110 casing are reduced 4.7% and 5.0%, respectively, and KISSC is reduced 41.4% in high temperature and high pressured sour environment with 80%σs, casing damage phenomenon is obvious, which provide a new method for evaluation of applicability and hydrogen damage of piping steels in high temperature and pressured environments in oil fileds.