The corrosion behavior of the hot-extruded SiCp/AZ91 (MMCs), a magnesium alloy AZ91 based composite containing different amount SiC particles (i.e. 2%, 5%, 10% and 20% in volume fraction), was investigated in 3.5%NaCl solution saturated by Mg(OH)₂ at 25 ℃ by means of mass loss method, electrochemical measurements, SEM and TEM observations and XRD. The results indicated that: The corrosion rate of the SiC_p/AZ91 MMCs was much greater than that of AZ91 magnesium alloy, and which increased as the increasing volume fraction of micron-sized SiC. The strengthening SiC particles exhibited little tendency with the alloy matrix to form galvanic couple, thereby little tendency to induce galvanic corrosion in micro-scale. But the addition of SiC particles resulted in a highly change in microstructure of SiC_p/AZ91 MMCs, as consequence, the corrosion resistance of the composite became significant inferior, in comparison with those of the AZ91 alloy. There were two main reasons responsible for the greater corrosion rate of SiC_p/AZ91 MMCs. Firstly, SiC particles promoted grain refinement of β phase, which increased the micro-galvanic corrosion current density between β phase and α phase. Secondly, the addition of SiC particles promoted the dynamic recrystallization nucleation of β phase at the interface SiC particles/AZ91 matrix, which might be beneficial to the microgalvanic corrosion of the coupling of β phase and α phase there, therewith indirectly increased the corrosion rate of SiC_p/AZ91 MMCs.

Susceptibility to stress corrosion cracking (SCC) of nickel based alloy 800H was studied in supercritical water at 550 ℃, 25 MPa, 600 ℃, 25 MPa and 650 ℃, 25 MPa respectively, and its general corrosion behavior in supercritical water at 650 ℃, 25 MPa and in subcritical water at 290 ℃, 15.2 MPa respectively as well. The mechanical properties of alloy 800H were also examined at different temperatures in air. The strain-stress curve of slow strain rate tensile (SSRT) tests shows that the strength of alloy 800H decreases as temperature increases. The ex situ scanning electron microscopy (SEM) observation shows that alloy 800H under the three conditions in supercritical water all exhibits susceptibility to SCC. The SSRT tests in air show that the yield strength and tensile strength of alloy 800H decrease as temperature rises. The results of general corrosion experiment in supercritical waters show that the weight gain of the alloy follows a parabolic law; however, in subcritical water the alloy exhibits mass loss.

The effect of preferred orientation on the corrosion behavior of hot-pressed and hot-deformed nanocrystalline NdFeB magnet was investigated by electrochemical measurements and materials analysis methods. The results indicated that the preferred orientation had little effect on the corrosion behavior of hot-pressed and hot-deformed nanocrystalline NdFeB magnet. Polarization and electrochemical impedance spectroscopy (EIS) measurements showed that the cross section vertical to the preferred orientation exhibited a higher dissolution rate and susceptibility to localized corrosion in 3.5%NaCl solution rather than that parallel to the preferred orientation. X-ray photoelectron spectroscopy (XPS) revealed that after immersion in 3.5% NaCl solution for 30 min, both of the surfaces of the two sections showed selective corrosion of Nd. The slight differences in the corrosion behavior of the two cross sections were probably ascribed to their differences in the Nd-rich phase proportions and the guantities of grain boundaries.

The crevice corrosion behavior of 5083 and 6061 aluminium alloys was investigated by electrochemical noise and in-situ measurement with microelectrode. The experimental results indicated that concerning the crevice corrosion process, 6061 alloy follows IR drop mechanism, while 5083 alloy follows critical solution composition theory. The corrosion of 5083 alloy was mainly uniform corrosion and transferred to severe localized corrosion with the increasing of crevice depth. But the 6061Alloy suffered from severe localized corrosion. The difference of corrosion behavior between 5083 and 6061 aluminium slloys might be attributed to the presence of different intermetallic phase for the two alloys.

The electrochemical behavior of high nitrogen stainless steel (HNS) in 1 mol/L NaCl solution with different pH values was investigated by means of potentiodynamic polarization curves, electrochemical impendence spectrum and current-time transient curves. The results show that anodic passivation of HNS could occur in alkaline solutions, while the corrosion rate of HNS decreased with the increasing pH value; a porous film might be grown on HNS in neutral NaCl solution due to the companying processes of dissolution and repassivation. In acidic and alkaline NaCl solutions, the formed passive films on HNS exhibit superior protectiveness rather than that in neutral NaCl solution.

Micro-arc oxidation coating on 6061 aluminum alloy was prepared in a Na₂SiO₃ containing electrolyte by a constant current control mode, and the effect of current density on the microstructure and performance of micro-arc oxidation ceramic coating was studied by a series of tests. Results for the above coatings show that their thickness and surface roughness increase with the increasing current density, however, their corrosion resistance decrease, and their hardness increases first and then decreases with the increasing current density. The ceramic coatings are mainly composed of α-Al₂O₃ and γ-Al₂O₃. As a comparison, a novel current control method was adopted to prepare a micro-arc oxidation coating. Accordingly, the amount of micro-cracks was significantly reduced, and the corrosion resistance was obviously enhanced for the coating prepared by the new mode.

The susceptibility to stress corrosion cracking (SCC) of several austenitic stainless steels AL-6XN, 316Ti and TP-347 in supercritical water at 550 ℃/25 MPa and 650 ℃/25 MPa respectively was studied by slow strain rate tensile test (SSRT). The strain-stress curve shows that the strength of these three steels decreases as temperature increases; the change in the fracture elongation of them shows different characteristics. The ex-situ scanning electron microscopy (SEM) observation shows that AL-6XN at 550 ℃and 650 ℃, and 316Ti at 550 ℃ exhibit a tendency of susceptibility to SCC, and the tendency of susceptibility to SCC of the three steels may be ranked as: AL-6XN/550 ℃>316Ti/550 ℃>AL-6XN/650 ℃.

Electrochemical performance was studied for 904L stainless steel after solution treatment at different temperatures in concentrated sulfuric acid by means of measurements potentiodynamic polarization curve and cycle polarization curve. The results show that the solution temperature has little effect on cathodic process, but varies the anodic polarization curve greatly. Whilst 904L stainless steel shows the best corrosion resistance after solution treatment at 1120 ℃ for 0.5 h.

A well ordered porous oxide film on aluminum alloy was prepared by a three-stage process in electrolyte of boric-sulfuric-oxalic acids. The relevant growth mechanism of oxide film in the processes with modes of galvanostatic and reduced voltage was elaborated. The morphology and microstructure of the oxide films were characterized by scanning electronic microscopy (SEM). The corrosion performance of the films in 3.5%NaCl solution was examined by electrochemical impedance spectroscopy and potentiodynamic polarization curves. The results show that the anodic film exhibits to be regular and dense with pore diameter of 10~13 nm. Moreover, the electrochemical behavior of anodic oxide film could be described as that the impedance and corrosion resistance was increased with the increasing thickness of the film and the cell wall.

In order to study the influence of CO₂ on the discoloration of red lead, which was immersed in deionized water, and solutions of NaCl, Na₂SO₄ and their mixture for 28 days at 25 ℃ while the test liquors are kept either in static atmospheric CO₂ or aerated with gaseous CO₂, respectively, then the color of the tested red lead was indexed according to the standard of coordinates L, a, b in color space. The results showed that red lead discolored most obviously in Na₂SO₄ solution, followed by in water, again in NaCl solution, the last in mixed salt solution. During test in the CO₂ aerated liquors, the red lead exhibits higher discoloration rates rather than that in the static atmospheric CO₂; the maximum difference of color aberration after 28 days for the two series tests was more than 2 times, specially. XRD tests showed that the red lead transformed from Pb₃O₄ to PbCO₃ and PbO₂ no matter test in static atmospheric CO₂ conditions or test in the CO₂ aerated liquors.

Electrochemical methods were applied to investigate the performance of zinc reference electrode in Zinc-Silver oxide primary battery at 10 ℃, which was constructed for trial of materials. After 10 minutes immersion in KOH solution, Zn electrode displayed a steady potential around (-1555±5) mV, corrosion current varied little which maintained at 2×10^-5A/cm² order, and resistances Z_Re and Z_Im in the capacitive arc of the AC impedance altered little. The results indicated that zinc electrode sustained small corrosion rate for long time immersion in 7 mol/L KOH solution, which provided a stable electrode potential and could be used as reference electrode in measurements such as trial of materials in Zinc-Silver oxide battery and other electrochemical tests in alkaline electrolytes.