The results of 8 year atmospheric exposure of 17 steels at 7 sites in China were examined. Some new concepts about the effect of time of wetness, pollution of sulfate and chloride were suggested. For carbon steels, humid and hot condition had significant effect during the long exposure. With addition of pollutants, severer corrosion might be observed. The applicability of international standard ISO9223, which illustrated the classification of corrosivity by means of meteorology and pollution data, was discussed. The relative corrosivity order arranged according to one year exposure data was different from that deduced from long term exposure results. It was not appropriate to evaluate corrosivity only by means of one year exposure.

The effect of additon of Na2S2O3 to boiling solution of 50%NaOH+0.3%SiO2 on SCC of Alloy 800 was investigated using C-ring tests along with anodic polarization measurements for Alloy 800, pure Cr, Ni and Fe. Na2S2O3 was found to stimulate the anodic dissolution and retard the passivation of Alloy 800. This was mainly attributed to the effect of S2O32- on the anodic polarization behavior of Ni. Addition of S2O32- gave rise to acceleration of caustic SCC of Alloy 800, and the maximum cracking rate was observed at ca. -40 mV (SCE).

The inhibitive action of thiourea (TU) on the corrosion behaviour of iron was investigated in 0.5mol/L H2SO4 solution by means of SERS spectra and electrochemical measurements. TU inhibited the cathodic and anodic reactions of iron. The inhibitor effectiveness increased with its concentration, reached a maximum (at about 1.25mol/L) and then decreased. TU in low concentrations inhibited the anodic reaction of iron by adsorption on active sites; TU in high concentrations participated in the anodic reaction of iron, and followed a Langmuir-type isotherm. The corresponding kinetics parameters were VTU =l,ba=118mV. TU was adsorbed mainly parallel to iron surface at low concentrations. However, TU inclined to be perpendicular to the surface as its concentration become higher.

AC interference of various amplitudes was intentionally introduced during the standard current efficiency measurements for AZ41 magnesium sacrificial anode in a saturated calcium sulphate-magnesium hydroxide solution, to simulated the long-term environment around magnesium anodes installed in the backfill. Different forms of ac auxiliary electrodes led to different current distributions on the anode surface and thus resulted in different morphology after the anode was subject to galvanostatic dissolution. Under the influence of ac interference, working potential of the anode obviously shifted towards noble and even became nobler than the open potential of iron at greater ac density. Polarization curves obtained in a Na2SO4+K3[Fe(CN)6]+K4[Fe(CN)6] solution indicated that corrosion product film on the anode had the character of n-type semiconductor. The current efficiency of the anode significantly dropped with the increasing ac density. XRD analysis revealed that magnesium hydroxide was still the unique corrosion product in the simultaneous presence of dc and ac currents.

The effects of Cl- and external magnetic fields on potentiostatic current oscillations in Fe/0.5mol·L-1 H2SO4 system were studied with electrochemical methods and holographic microphotography. The imposed magnetic field influenced the current oscillations by speeding up the mass transfer and leading to the increase in the ratio of activation time to passivation time (ta/tp). The addition of Cl- inhibited the growth of the passive film, resulting in the increase in the ta/tp, and positive shifting and narrowing down of the oscillation potential range. The existence of both the magnetic field and C- had concurrent influence on current oscillations, which might be brought about chiefly by the increase in the magnetic susceptibility of the substance formed at the iron/solution interface.

The effect of a sputtered Ti-50Al-10Cr coating on oxidation resistance of TiAl intermetallic compound was investigated in static air. The bare TiAl alloy exhibited poor isothermal and cyclic oxidation resistance at 800-1000℃ due to the formation of TiO2-based scales which tended to spall during cooling. The sputtered Ti-50Al-10Cr coating could remarkably improve the oxidation resistance of the TiAl alloy by means of the formation of adherent Al2O3 scale. After long-term oxidation (at 900℃ for 1000h), TiAlCr still provided an excellent protection for TiAl alloy and only a slight interdiffusion occurred as a result of the inward diffusion of Cr while no voids were found at the coating/substrate interface. The TiAlCr coating combined better oxidation resistance with its compatibility to substrate than any other conventional aluminide and MCrAlY coatings.

The corrosion resistance of passivated films on electrodeposited Zn-Fe, Zn-Co, Zn-Ni alloys was 2-4 times higher than that on Zn. Results of XPS and AES showed that all these passive films were composed of CrO3, Cr2O3, Zn(OH)2, ZnO and H2O, and the relative contents of CrO3/Cr2O3 and Zn(OH)2/ZnO were basically the same. The only difference was that the total content of Cr in passivated film on electrodeposited zinc alloys was higher. It led to an integrated and fine protective film, which possessed self-repair ability. In addition, the presence of an iron-group metal enriched layer obstructed the corrosion process.

Stress corrosion cracking of duplex stainless steels may occur in H2S saturated aqueous solutions containing Cl-. In this study, metallographic microscopy, EPMA, and SEM were used to analyse the cracking behaviour of the duplex stainless steel 00Cr18Ni5Mo3Si in different solution. In solution (b) : saturated H2S+5%NaCl+0.5%CH3COOH, pH=3.0-4.5 and solution (c) : saturated H2S+5%NaCl+0.5%CH3COOH+ 0.01%Na2CO3, pH=4.3-4.6, selective corrosion of individual phasses was observed during stress corrosion cracking. The ferrite corroded while the austenite was not attacked. In solution (d): saturated H2S+0.5%NaCl+0.5%CH3COOH+HCl(pH≈1), on the contray, the austenite corroded and the ferrite was only slightly attacked. Perhaps the potential reversal of the austenite and the ferrite took place in the presence of HC1 in the H2S saturated solution.

EIS investigation of epoxy coating containing anti-rust pigment Pb3O4 was made. On the basis of various specific equivalent circuits for the coating, the performance mechanism of Pb3O4 in the organic coating was discussed. The EIS results showed that Pb3O4 was a typical passive pigment. At the initial stage of immersion , Pb3O4 dissolved and then diffused towards the metal/coating interface. It resulted in the formation of passive film and anodic dissolution of the metal was inhibited. Later the passive film might be destroyed and a saponification film could form. At that time the corrosion rate determining step was changed from metal dissolution control to oxygen definite-layer diffusion control.

The inhibition behaviour of BTA and PTD in borax solution for copper was studied by using pho-toelectrochemical technique. The potential φv, at which Cu2O on the electrode was completely reduced to Cu, was applied to characterize the interaction of Cu2O layer with the film, for example, Cu(I) BTA, formed from inhibitor on the Cu electrode. The more negative the φv, the more efficient the inhibitor. BTA might function as stabilizing Cu2O film on the surface. The corrosion resistance of copper was dependent on the Cu2O film. The inhibitive action of both BTA and PTD on Cu electrode was compared by photoelectrochemical method. The results were in agreement with those of ac impedance measurements.

The corrosion prevention ability of acrylic latex coatings could be enhanced by introducing silane coupling agent into coating/metal interface. The effects of coupling agent type, its contents, curing temperature and application procedure on the anticorrosion behavior were investigated. Electrochemical impedance spectroscopy(EIS) and adhesive strength measurements were used to assess the corrosion prevention performance of the modified coatings. The results showed that the steel substrate pretreated with methacryloxypropyl trimethoxysilane(A174) and cured at 120℃ exhibited excellent anticorrosion performance, which could be attributed to the formation of a new interfacial layer with high hydrophobicity and strong adhesive strength.

The effect of microwave plasma treatment on corrosion resistance of Ni-base amorphous alloy coatings (Ni-W, Ni-W-B, Ni-Mo-P) was investigated. It was found that the treatment improved their corrosion resistance in H2SO4, HNO3, HC1 solutions. The microwave plasma treated ammorphous Ni-W composite coatings (with 5wt% ZrO2 or Al2O3 particles) exhibited higher oxidation resistance during the heating at 700℃ for l-28h. As anodic polarization curve indicated, the microwave plasma treated amorphous Ni-W composite coating had wider passivity potential range. The corrosion resistance of Ni-base amorphous alloy coating was dependent on the power and time of microwave plasma treatment.

By means of complex variable function theory, an analytical solution of couple corrosion current inside the tube with a longitudinal weld was obtained. The system was simplified as two dimensional. The effect of tube diameter and weld width on couple corrosion current was examined. For a fixed weld width, the larger the tube diameter, the larger the corrosion current

In this article, the diffusion geometry in double glow plasma surface alloying(DGPSA) was treated as vapor-solid diffusion couple. The concentration distribution of tungsten in the commercially pure iron sample after DGPSA was determined by SEM. The regression equation describing concentration profile for tungsten, y(x) = 2.3698 - 7.8711 ×10-3x + 6.377 × 10-6x2, where y-the concentration of W in α-Fe and x-the distance from sample surface, was established by multi-element regression. The plot of ln[-y'(x)] versus x2 was given, on which all the experimental points fell on a straight line except a few points near x=0. These results illustrated that the vapor-solid diffusion couple was reasonable for diffusion geometry of plasma surface alloying. The diffusivity for tungsten in α-Fe was calculated from the plot of ln[-y'(x)]versus x2.