Alumina coating has excellent thermal stability at elevated temperatures, this can provide a good diffusion barrier to withstand high temperature oxidation and therefore, increase their life time in aggressive atmospheres. With the industrial development, water vapour is present in nearly all atmospheres where alumina forming alloys are used at high temperatures for industrial process. The most important problem is that how to maintain excellent performance of alloy in humid atmospheres. This paper summarizes the effect of water or water vapour on the stability of alumina scales, growth kinetics, film adherence and alumina film surface morphology.

Fine-grained γ'-Ni₃Al coatings were developed by a two-step process: co-electrodeposition of Ni with Al particles and subsequent annealing in vacuum at 600℃ or 800℃. After oxidation at 1000℃ in air for 20 h, the scales formed on both coatings exhibited better adhesion than that on a coarse-grained Ni₃Al alloy, because the fine-grained coating structure suppressed the formation of voids at the scale/metal interface. Moreover, the scale formed on the coating by annealing at 800℃ consisted of NiO, NiAl₂O₄ and Al₂O₃, while the scale on the coating by annealing at 600℃ consisted of NiAl₂O₄ and Al₂O₃. The reason for this result is related to that the latter coating had a finer-grained structure, which promoted rapid formation of a continuum layer of Al₂O₃.

In this paper, double-loop electrochemical potentiokinetic reactivation (DL-EPR) and dynamic electrochemical impedance spectroscopy (DEIS) by forward and reverse potential scan have been used to investigate sensitized ferritic stainless steel 00Cr12Ti exposed to 0.1 mol/L H₂SO₄+0.0001 mol/L KSCN solution and fitted with proper equivalent circuits. The results indicated that the region distribution of DEIS is in accordance with that of DL-EPR, including activation region, transition region, passivation region and reactivation region. In the passivation region, the capacity loop shrunk at about 0.2 V, and the real part of EIS curve at the low frequency decreased even became negative. The main reason is that the passive film is not complete and a part of fresh surface is exposed to the solution. In the reactivation region, before occurrence of intergranular corrosion, at about 0.2 V, the capacity loop decreased dramatically, and then gradually increased. At the low frequency the EIS displays a capacitive loop with negative resistance, this implies that the passive film suffers rupture and repair due to depletion of Cr at the grain boundary. An inductive loop which is ascribed to the adsorption of intermediate product on the electrode surface indicates that the diffusion process of the intermediate product predominated the corrosion reaction. The degree of sensitivity (DOS) expressed by the ratio of the reciprocal of the minimum R_ct in the reactivation region to activation region on DEIS is the same as the DOS from DL-EPR.

This paper focuses on the influence of ultra-fine glass fiber on the coating properties. Diglycidyl ether of bisphenol-A and diglycidyl ether of bisphenol-F epoxy resins were used as film former. Salt spray test and electrochemical impedance spectroscopy (EIS) were employed to characterize the anticorrosion properties of the coatings. Experimental results indicate that the diglycidyl ether of bisphenol-A epoxy resin can improve the coating hardness, while the diglycidyl ether of bisphenol-F epoxy resin has better anticorrosion properties.

A new prediction model was proposed to calculate the flow accelerated corrosion (FAC) rate in reducer, which was coupled the steady-state mass transfer model electrochemical theory and one-dimensional galvanic corrosion model. Firstly, the steady-state mass transfer model was used to obtain the distribution of concentration polarization current density and the concentration polarization corrosion potential of velocity extreme point near the wall of reducer. The galvanic corrosion current density was calculated by substituting the potential into one-dimensional galvanic corrosion model. The new model was employed to calculate the reducer; the results showed that the corrosion current density of large-end was larger two orders than that of small-end. Compared with the FAC rate calculated by the wall shear stress theory, presented by Efird and Cheng, or by purely steady-state mass transfer theory, the results obtained by the new model have good agreement with the practical situation which were counted 2000 pipe fittings in Taiwan nuclear power plant by Kuen Ting. The statistical result showed that the large-end of reducer appeared the maximum of reduction of thickness.

U-bend immersion tests were used for studying the stress corrosion cracking behaviors for electroslag welding (ESW) Alloy 600, electroslag welding (ESW) Alloy 690 and submerged-arc welding (SAW) Alloy 690. Results showed that electroslag welding Alloy 600, electroslag welding Alloy 690 and submerged-arc welding Alloy 690 samples were immune to stress corrosion cracking in simulated primary water of pressurized water reactor (PWR) after being immersed for 1193 h, which contained 1.5×10^-3 B, 2.3×10^-6 Li, 2.5×10^-6 H₂ at 325 ℃, 15.8 MPa. However, stress corrosion cracks were observed in electroslag welding Alloy 600 after being immersed in 10 wt.% NaOH alkali solution for 720 h at 330℃, 11 MPa. The maximum crack length was 835 μm after 720 h immersion and further expanded to 1135 μm after 1440 h immersion with a typical intergranular stress corrosion cracking (IGSCC) characteristic. For electroslag welding Alloy 690, microcracks were initiated with the length of 0.3 μm to 1.15 μm and stress corrosion crack was not observed.

The scanning electron microscopy (SEM), atomic force microscopy (AFM) and surface profilometry were employed to characterize the surface conditions of Alloy 690TT samples. The corrosion behaviors of Alloy 690TT samples with different surface conditions were compared by potential of zero charge (PZC), potentiodynamic polarization curves and electrochemical fast and slow scan. The experiment results showed that the surfaces ground to 400# were much rougher than the mechanically polished surfaces and surface roughness of the former was bigger than the latter. The corrosion rate of the ground surfaces was bigger and the ground surfaces were more sensitive to stress corrosion cracking (SCC), compared with the mechanically polished surfaces in the same corrosive environment. That corrosion of Alloy 690TT could be accelerated by single surface roughness or single surface residual strain. The difference of corrosion rate and the sensitivity of SCC in this experiment were affected by surface roughness and surface residual strain simultaneously.

The corrosion behaviors of high strength aluminum alloy 7A04 in three different experimental conditions have been investigated by scanning electron microscope (SEM), energy dispersive X-ray detection (EDX), Fourier transform infrared(FTIR) and mass loss method, and the relativity has been analyged  with the result of Jiangjin atmospheric environment. The results show that the corrosion product increases with testing hours prolonging, and the mass loss of corrosion product obeys the exponential rule as C=A•tⁿ. Surface observation shows that corrosion product is agglomerated and extended forth. The corrosion products are made up of alumina, aluminum sulfate hydrate and aluminum chloride. The simulation results for the aluminum alloy 7A04 at cyclic wet-heat conditions (40℃,8 h; 25℃, 16 h; 95% RH) in the 0.067% SO₂ polluted environment had better correlation with Jiangjin exposure result according to the mass loss data in all simulation methods in the paper.

Biofilm is one of the main factors that influence metal corrosion. According to the structure and property of biofilm, the compound of natural biopolymer agar and SRB cells were deposited on 907A surface. Artificial biofilm was produced. The dissolved oxygen concentration in artificial biofilm was studied by microsensors. Environmental scanning electron microscopy (ESEM) and energy dispersive X-ray detector (EDAX) were used to study 907A corrosion under artificial biofilm. The result indicated that the oxygen concentration became lower and lower with the distance between metal surface and test location becoming small. The corrosion morphology and corrosion products of 907A were influenced by environment.

The corrosion behavior of two commercial steels NF616 and 12CrMoV was comparatively investigated at 600℃ in H₂-CO₂, H₂-HCl-CO₂ and H₂-HCl-H₂S-CO₂ reducing atmospheres. In comparison with corrosion behavior of the same-type steels in H₂-CO₂ and H₂-HCl-CO₂ reducing atmosphere, NF616 and 12CrMoV suffered from accelerated corrosion in the H₂-HCl-H₂S-CO₂ atmosphere, particularly the degradation of chromia formed on 12CrMoV. The kind of accelerated corrosion was mainly attributed to formation of metal chlorides and sulfides during corrosion procedure. The mechanism on accelerated corrosion is illuminated on the basis of thermodynamic diagrams.

A new Te-Ni-Cr alloys were prepared by powder metallurgy technology and the corrosion resistance of Te-Ni-Cr alloys were studied by OM, SEM, EDS and XRD in the 3.5% sodium chlorine solution. The results show that the microstructure of the alloys are changed by Te. There are bone-like dark gray structure on the surface of the alloy, playing protective role. Ni₂O₃ and iron oxide were determined by the analysis of XRD. The calculated corrosion rate shows that Te-Ni-Cr alloy increases the corrosion resistance than tellurium-free alloy.

The corrosion behavior of Al-0.63Mg-0.28Si alloy under MgCl₂ solution drops with initial concentration of 0.05 mol/L~0.3 mol/L and volume of 6 μL in the environment of relative humidity (RH) 75% and RH 33% were studied by using Kelvin Probe. In these two environments, because the water in the drop is evaporated, a thin MgCl₂ solution layer with a diameter of about 2.9~3.2 μm forms on the alloy surface. As the open circuit potential (OCP) baseline keeps stable at -0.3~-0.5 V_vs \ SHE, there exists potential noise that the OCP repeatedly exhibits a sudden decrease and then immediate recovery, which is associated with initiation and re-passivation of metastable pits with diameter less than 3 μm. When the OCP baseline decreases slowly to -0.7~0.8 V and keeps stable low, stable filiform-like corrosion occurs and develops. In the environment of RH 33%, only metastable pitting corrosion occurs within 24 h. In the environment of RH 75%, as the initial MgCl₂concentration is 0.3 mol/L and 0.2 mol/L, the main corrosion form is metastable pitting corrosion. As the initial concentration is reduced to 0.1 mol/L, stable filiform-like corrosion always occurs on the drop edge and grows outward. As the initial concentration is further decreased to 0.05 mol/L, the likelihood of stable corrosion is lowered, and the main corrosion form is metastable pitting corrosion within 24 h. The number of metastable pits every unit time is increased with RH of the environment. Meanwhile, in environment of the same RH, it is increased with the decrease in initial concentration.

The corrosion resistance property in artificial seawater of 17-4PH steel after different heat treatment processes was investigated by electrochemical tests, and the corrosion morphology and microstructure were also analyzed. The results indicated that after solution and intermediate treatments the steel showed the best corrosion resistance property and excellent mechanical properties while aging at 520℃ for 4 hours. The microstructure became finer and the precipitation in grain boundaries increased with the increase of aging temperature and time in a certain range. The reverted austenite and copper precipitates that separated out while aging treatment were the major determinants of the corrosion resistance property of 17-4PH steel.

The interactions between five kinds of amino acid corrosion inhibitors, i.e. glycin、leucine、aspartic acid、arginine and methionine and (100), (110), (111) crystal surfaces of Fe have been simulated by molecular dynamics. The results show that the orders of binding energy for five kinds of amino acids with three Fe crystal surfaces are as follows: glycing(r) of all systems indicates that binding energies are mainly provided by coulomb interaction energy and Van der Waals energy. Coordination bonds are formed between the metal iron atoms and the nitrogen、oxygen and sulfur atoms in amino acids. The configurations of amino acids have been deformed during their combining with Fe crystal surfaces, but the deformation energies of amino acids are far less than respective nonbonding energies.  

Semiconductor properties of the passive film formed on 304L stainless steel (SS) in high-temperature and high-pressure water with (or no) zinc addition were investigated using anodic polarization curves, Mott-Schottky plots and photocurrent method in buffer solution. And the donor density, flat band and band gap were analyzed to investigate the effect of zinc addition on the passive film particularly. The results indicated that the passive film formed on 304L with zinc addition was composed of many layers; the passive film with zinc addition behaved as a n-type semiconductor, a p-type with no zinc addition; the flat band shifted negatively; the carrier concentration reduced; It was concluded that zinc addition had great influence in the structures and semiconductor properties of 304L stainless steel (SS).

Corrosion mechanism of Tremie pipe of W0714 film evaporator of hexanolactam was investigated by chemical method, optical microscope and SEM etc.. the results showed that the non-sensitive intergranular corrosion took place on the Tremie pipe in the non-oxidizability medium. the potential of 304L SS in the medium was located at the transpassivation region, which resulted in the corrosion of the Tremie pipe.