As the first barrier for deep geological disposal of high-level nuclear waste (HLNW), HLNW containers are of great significance. Because of the superior corrosion resistance, Ti is one of the candidates. Once the oxygen in the repository is depleted, the cathodic process supporting Ti corrosion is mainly H⁺ reduction. Therefore, Ti and its alloys are likely to suffer from hydrogen embrittlement (HE), which in turn greatly shortens their service life. The environmental factors, which may induce HE for Ti and its alloy during deep geological disposal, were introduced. The hydrogen diffusion and the relevant mechanism of HE for Ti and Ti-alloys are discussed in the article. Furthermore, the relevant information of critical hydrogen concentrations of various Ti-alloys was also summerized, which is a useful index for predicting whether HE may happen or not. The possibility of hydrogen embrittlement for Ti container in deep geological environment was analyzed. Finally, the future research trend on HE of Ti container in deep geological disposal environment is expected briefly.

Corrosion is one of the main causes of metal material failure. In corrosion research, it is difficult to obtain accurate information on the corrosion evolution. The development of spatial-resolution technology enables the in-situ observation of metal corrosion processes to be realized. By combining the spatial-resolution technology and electrochemical techniques, more microscopic metal corrosion information can be obtained, which facilitates more accurate acquisition of corrosion information and provides reliable support for the illustration of corrosion mechanism. This paper reviews several classical spatial-resolution techniques in the field of corrosion in terms their working principle, advantages and disadvantages etc. The industrial CCD camera, digital holographic surface imaging technology, X-ray computed tomography, optical microscope, scanning electron microscope, atomic force microscope and transmission electron microscope are introduced. The application status and development prospects of each technology in the field of in-situ monitoring of metal corrosion are discussed. Finally, these spatial-resolution techniques are compared and corresponding recommendations for use are proposed in the review.

The performance of the Al-Zn-In-Mg-Ti sacrificial anode, which is usually used in shallow sea area, was studied in a simulated deep-sea water of low dissolved oxygen via weight loss measurement, galvanostatic method, potentiodynamic polarization curves, electrochemical impedance spectroscopy and cyclic voltammograms test and scanning electron microscope (SEM/EDS), in terms of the open circuit potential, work potential, actual electric capacity, electric current efficiency and corrosion morphology of the Al-Zn-In-Mg-Ti sacrificial anode. It was found that, the dissolution rate of the Al-Zn-In-Mg-Ti sacrificial anode decreased in the simulated seawater of a low dissolved oxygen. The re-deposition process of the active elements was suppressed and the oxide scale on the anode surface was hard to be dissolved. Correspondingly, both the discharge performance and the current efficiency decrease, therefore a corresponding design margin should be set aside in the design course of cathodic protection.

The corrosion behavior of 304 stainless steel in acidic FeCl₃ solution was studied by linear sweep voltammetry and cyclic voltammetry. The results show that the free-corrosion potential of 304 stainless steel shifts positively and the free-corrosion current density increases with the increase of Fe³⁺ concentration at the same pH and Cl^- concentration. When 304 stainless steel is corroded in acidic Fe³⁺ solution, the free-corrosion potential of stainless steel is positively shifted due to the presence of Fe³⁺ reduction reaction, which makes it difficult for H⁺ reduction reaction to carry out on the electrode surface. When Fe³⁺ content is sufficient, the cathodic reaction in stainless steel corrosion process is mainly Fe³⁺ reduction reaction, not H⁺ depolarization reaction. Therefore, it should be fully considered the effect of Fe³⁺ on pits growth in the study of pitting corrosion behavior of stainless steel.

The effect of sulfate-reducing bacteria (SRB) and applied stress on the corrosion behavior of 17-4 PH stainless steel was studied in a simulated marine solution inoculated with SRB. The stress-strain curves and fracture morphology were analyzed to acquire the differences in corrosion behavior induced by sterile solution and SRB inoculum solution respectively. The results showed that the I_SCC values were increased by 5.2%, 9.3%, and 4.4% in the SRB-inoculated solution for the steels subjected to single stage aging, double stage aging and tempering treatments respectively. The corrosion product of FeS enhances the anodic dissolution process and accelerates the corrosion reaction. Double stage aging treated steels are more sensitive to SRB due to the microstructure of coarse martensite, facilitating the entry and accumulation of hydrogen. The stress corrosion cracking (SCC) mechanism for single stage aging and tempering treated steels may be ascribed to the anodic dissolution (AD), while the double-stage aging treated steel may be due to the hydrogen induced cracking (HIC).

Due to the good oxidation resistance and high creep strength, austenitic steel is widely used in the construction of supercritical power station boilers, such as boiler super-heater and re-heater tubes, and thus its oxidation resistance in supercritical water is receiving more and more attention. The oxidation characteristics of austenitic steel HR3C and Sanicro25 are studied in supercritical water at 650 ℃/25 MPa and 700°C/25 MPa for 1000 h. The surface morphology, cross-sectional morphology, element distribution and phase composition of the formed oxide scales on the steels are characterized by means of SEM, XRD and Raman spectroscopy. The results show that the formed oxide scales on HR3C and Sanicro25 in supercritical water present a double layered structure, that is to say, the outer layer is composed of Fe-rich nodular oxide, and the inner layer consists of Cr-rich dense oxide. The oxidation rate of austenitic steel HR3C and Sanicro25 in supercritical water increase significantly with the increase in temperature. The curves of oxidation mass gain vs time may be fitted with exponential functions with exponents of 0.46 and 0.66 at 650 ℃, as well as 0.42 and 0.22 at 700 ℃ for HR3C and Sanicro25 respectively. There are small differences in oxidation mass gain between the two austenitic steels. The phase composition of the oxide scales on austenitic steel HR3C and Sanicro25 is basically the same for a given temperature, while Cr₂O₃ is detected. In addition, pores are observed in the outer layers on the two steels oxidized at 700 ℃, which may act as short circuit for oxygen inward diffusion. The results also show that austenitic steel HR3C and Sanicro25 have similar resistance to high temperature oxidation in supercritical water. The influence of temperature on the formation process of the oxide scales on austenitic steel HR3C and Sanicro25 and the process of the formation of nodular scales are also discussed briefly.

The effect of phosphating on the fracture behavior of a domestic SA-540 B23 steel used for nuclear reactor coolant pump bolt is studied by scanning electron microscope (SEM), hydrogen content analysis and in-situ hydrogen charging slow strain rate test (SSRT). The result shows that phosphating treatment has no effect on the fracture properties of B23 steel. Hydrogen content analysis shows that hydrogen is mainly distributed in the phosphate coating instead of the substrate. Hydrogen embrittlement tests show that B23 has obvious hydrogen embrittlement susceptibility under the attack of hydrogen, and the fracture feature is intergranular cracking.

The Cu segregation in Cu-containing steel was investigated after high temperature treatment at 1150 ℃ in air for different time. It is found that Cu segregation occurred both at the interface oxide scale/steel matrix and at grain boundaries of the sub-surface of the substrate beneath the interface, which was caused by the preferential oxidation of Fe and the decarburization, thereby resulted in the sharply decrease of the cementite content near the steel surface. It also found that the Cu content in the area beneath the interface oxide scale/steel matrix for the heat treated steel is lower than that of the steel before subjecting to heat treatment.

The effect of chemical composition and microstructure on the corrosion behavior of Mg-alloys AZ31, AZ91, AM60 and ZK61 in 0.1 mol/L sodium chloride solution (NaCl) containing different concentration of ammonium nitrate (NH₄NO₃) were investigated. The corrosion processes of the four Mg-alloys were studied by immersion tests, polarization curve measurement, SEM and CLSM. Results show that the addition of NH₄NO₃ accelerates the corrosion of the four alloys, whilst autocatalytic pitting corrosion occurs due to the synergistic effects of Cl^-, NH₄⁺, and NO₃^- in solutions within a specific concentration range. The corrosion resistance of different Mg-alloys is closely related to the chemical composition and microstructure of the alloys.

The article aims to develop a new processing technique to efficiently improve the corrosion resistance of Mg-alloy, thus ultrasonic surface rolling process (USRP) was applied to modify the corrosion resistance of extruded AZ31B Mg-alloy. The grain size and surface morphology as well as the corrosion behavior of AZ31B Mg-alloy before and after ultrasonic surface rolling were comparatively examined by means of metallomicroscope and scanning electron microscopy, white light interferometer and electrochemical impedance spectroscopy. The results implied that USRP has significant influence on the grain size and surface morphology, in turn it has important influence on the corrosion behavior of AZ31B alloy. Compared with the bare alloy, the corrosion product film on USRPed alloy was much uniform and dense, while after removal of the corrosion products, small and dense corrosion pits could be seen on the Mg-alloy surface. The passivation film resistance (R_f=9020 Ω) of the treated alloy was much larger than that (R_f=14.8 Ω) of the bare alloy in the early stage of immersion. The impedance characteristic caused by the diffusion process appeared on the impedance spectrum of the bare alloy in the middle of immersion. At this time, the film resistance R_f=22.9 Ω, which is much smaller than the film resistance R_f=19800 Ω of the USRPed alloy. In the late stage of immersion, the passivation film resistance was R_f=31400 Ω for the USRPed alloy, while R_f=14400 Ω for the bare Mg-alloy. It follows that the ultrasonic surface rolling process could reduce the surface roughness, and refine the grains of Mg-alloy, thus increase the uniformity and compactness of passivation film on Mg-alloy, namely retard the electrochemical reaction process on the alloy surface, therewith reduce the occurrence of local pitting, then reduce the corrosion rate of Mg-alloy.

In view of the complexity of the corrosion for reclaimed water pipe, the corrosion behavior of coupons of reclaimed water pipe (ductile iron pipe without lining) in collected reclaimed waters with varying pH, total hardness, SO₄^2-- and Cl^--content was characterized by means of weight loss measurement, potentiodynamic polarization measurement and electrochemical impedance spectroscopy. The results indicated that: the instantaneous corrosion rate obtained by electrochemical test and the average corrosion rate obtained by weight loss method of the coupons are consistent with the variation of corrosion scale resistance. The orthogonal experimental results show that the effect degree of water parameters on corrosivity of reclaim waters may be ranked corresponding to the following order: pH＞total hardness＞SO₄^2-＞Cl^-. The slightly acidic water with low hardness was apt to cause corrosion of the pipeline coupon, and the water of low pH value presented the most obvious effect on the corrosion of the pipeline coupon. The alkalescent water could promote the formation of scales on the pipeline coupons so that to act as a protective scale for the substrate. However, the higher the anion concentration of waters, the smaller the diffusion impedance of the scale, and the more unstable the scale.

Corrosion inhibition films of 2-aminobenzothiazole (ABT), benzotriazole (BTA) and mixtures of ABT to BTA on Cu surface were fabricated through molecular self-assembled process and then characterized by means of field emission scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy (RAM) and optical Contact Angle (CA) measurement, while their corrosion inhibition behavior at 25 ℃ in 3.5% (mass fraction) NaCl solution was assessed. Two factors, namely the molar ratio of ABT to BTA of their mixtures and the dose of the mixture on the corrosion inhibition behavior were studied, respectively. When the dose of the inhibitors mixture was 20 mmol/L with the molar ratio was 1:1, its corrosion inhibition efficiency could reach up to 96.34%. The inhibition mechanism of ABT and BTA were acquired through kinetic analysis. Results confirmed that there exist physical absorption and chemisorption for all of them. The corrosion inhibition performance of complex films of the two inhibitors was better than that of every single inhibitor. The relevant collaborative parameters were calculated for predicting the performance of synergistic effect.

Aiming at the proposed potentiostatic pulse electrodeposition of Cu-Sn alloy, the influence of process parameters on the composition, grain size and corrosion resistance of prepared coatings is studied. The morphology, grain size, chemical composition and corrosion behavior of the Cu-Sn coatings electrodeposited by potentiostatic pulse technology or constant-current pulse technology are characterized by means of scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS) and electrochemical workstation. It is found that potentiostatic pulse process of Cu-Sn electroplating with the duty ratio of 33% and potential of 3 V could reduce the dissolution probability of the plating layer and maintained the complex ion migration and deposition driving force, so that the high-tin bronze coating can be obtained on parts of different size. The grain size of the coating on the part with surface area 78.5 mm² is less than 100 nm. Under the same initial conditions, the electrodeposition rate of the potentiostatic pulse technology is faster than that of the constant current pulse technology, besides the plated alloy presents much better composition uniformity and the formed coating possesses only few of pores and crystallite clusters, therefore the coating exhibits corrosion resistance 2 times higher than that made by constant-current pulse. Compared with the constant current pulse technology, the potentiostatic pulse electrodeposition is beneficial to improve the quality and corrosion resistance of copper-tin plating and which may facilitate the introduction of processing automation or composition control for complex parts as well.

Referring to the standard API 581 and considering the field environmental situation as well as the relevant corrosion mechanism of pressure vessels, a quantitative analysis method has been proposed to analyze and calculate the damage coefficient of various type, failure probability and failure consequence for pressure vessels. The risk levels of the pressure vessels may be differentiated as several grades, in accordance with the established risk acceptance criteria. Therewith, a proper plant related with schedule, content and measures of inspection, as well as, the relevant control of risk consequences may be formulated for high-risk vessels and components. The research results can be beneficial to the accurate and quantitative evaluation of the risk degree of pressure vessels, and the confirmation of relevant inspection plant for risks. The proposed method is of great significance to the reasonable allocation of human and financial resources for the on-site inspection and the safe production control of platforms. In conclusion, this method has been successfully applied to FPSO in the China sea and may further be adopted as a reference for other projects.