The paper focused on issues concerning the micro-arc oxidation (MAO) coatings on Mg-alloys, therefore, the formation of micro-defects and the relevant impact factors were summarized. The effect of micro-defects on the corrosion-resistant performances and application of MAO coatings were analyzed. Moreover, identification techniques and post-treatment methods for MAO coatings were introduced. Finally, research topics for micro-defects in MAO coatings in the future were proposed.

Structural materials in nuclear power plants are subjected to corrosion fatigue (CF) during long-term service in high temperature pressurized water. The mechanism and data base of CF crack growth are essential to the design, operation and life management of nuclear power plants. This paper reviewed the present research status on CF crack growth behavior. The effect of environmental, mechanical and material’s factors were introduced, while the fatigue crack growth model was discussed by taking the environment effect in high temperature pressurized water into consideration. Challenges and trends for research of fatigue crack growth mechanism and model for structural materials in nuclear power plants were also briefly addressed.

Layered double hydroxide (LDHs) is a type of layered compound composed of positively charged metal hydroxides and negatively charged anions. LDHs has the unique advantages of ion exchange, adjustable structure, good thermal stability and low manufacturing cost, therefore, it is an important class of inorganic nanocontainer material, and has a wide range of applications in the fields of flame retardancy, catalysis, water treatment, drug sustained release, etc. In recent years, LDHs has been proven to be able to load corrosion inhibitors and release them into the environment through ion exchange, which has become a major research hotspot in the field of anti-corrosion coatings. In this article, the anti-corrosion mechanism, influencing factors of LDHs materials, the research progress of various types of LDHs anti-corrosion coatings were summarized. At the same time, problems and solutions related with the application process were also analyzed. On the other hand, the relevant progress of LDHs anti-corrosion coatings in terms of multi-functionalization and compounding was summarized and prospected.

How to improve the comprehensive performance of nickel-aluminum bronze (NAB) alloys, has become an imperious demand, especially their corrosion resistance in more severe seawater environments. In this paper, the corrosion characteristics of NAB alloys and the relevant influencing factors were systematically discussed. The common methods of improving corrosion resistance, such as surface modification and casting processing were proposed. It is expected that the corrosion resistance of NAB alloys can be further improved with appropriate alloying approach and adjusting of the alloy composition. Finally, the future research and development directions were also prospected.

The research progress of the influence of Cl^- and SO₄^2- on the corrosion of austenitic stainless steel is reviewed. The corrosion mechanism of austenitic stainless steel and the influence of Cl^- and SO₄^2- on the corrosion of stainless steel are described, meanwhile, the reasons why SO₄^2- can inhibit the corrosion of stainless steel in chloride solutions proposed by different researchers and their opinions differ are summarized and discussed . Finally, suggestions for future research directions are put forward.

The failure behavior of epoxy glass flake coating in artificial seawater of various states, namely atmospheric static (0.1 MPa-0 m/s), atmospheric flowing (0.1 MPa-4 m/s), high hydrostatic pressure (10 MPa-0 m/s) and pressured-flowing (10 MPa-4 m/s) was studied by means of water absorption test, EIS, adhesion test, SEM, FT-IR, etc. The results indicated that, under the action of pressured-flowing artificial seawater, the interfacial bonding strength between pigments with the coating matrix may be significantly weakened, the structure of the coating is severely damaged, which promotes the diffusion of corrosive media in the coating, and in consequence, a large amount of water accumulates in coating defects and the interface of coating/metal, which result in significant increase in the water absorption rate and severe decrease in mechanical properties, as well as in rapid loss of coating adhesion and bubbling of the coating, as a result, the coating fails quickly. Finally, the failure mechanism of organic coatings induced by pressured-flowing artificial seawater was also discussed.

An ammonium salt surfactant containing thiadiazole (MTOTB) was synthesized as a novel inhibitor, aiming to combine the characteristics in corrosion inhibition and bactericidal property of heterocyclic compound and ammonium salt surfactant. The structure, surface activity and corrosion inhibition performance for carbon steel in simulated seawater with SRB of the prepared product were characterized by means of ¹HNMR, ESI-MS, FT-IR, surface tension measurements, electrochemical measurements and SEM-EDS. The results showed that the critical micelle concentration was 0.11 mmol/L for MTOTB in the simulated seawater. The inhibition efficiency could reach 95.81% for carbon steel in the simulated seawater with SRB for 21 d through addition of 0.2 mmol/L MTOTB. The results of SEM-EDS and XPS showed that MTOTB could adsorb on the surface of carbon steel effectively, so that inhibit the microbial corrosion of carbon steel.

The electrochemical corrosion behavior of X70 steel and its weld in a Cl^--containing Na₂CO₃+NaHCO₃ solution by various applied potentials was studied by means of electrochemical noise (EN) technique. Statistical analysis was conducted on the EN data to obtain the specific spectrum to characterize the initiation and development of the pitting. The results showed that the EN technique could effectively monitor the pitting process of X70 steel, while the amplitude of current noise reflected the initiation and development process of localized corrosion. When X70 steel was anodic polarized, the energy density spectrum (EDP) of EN moved from low-order zone to high-order zone, correspondingly, the pitting developed from metastable state to steady state. When the applied potential was in the activation-passivation zone, the EDP located in the metastable pitting zone. When the applied potential rose to stable passivation zone, the EDP of the substrate corresponds a pitting initiation period and the pitting resistance of the substrate was better. While the EDP for the weld with higher energy indicated that a small amount of steady-state pitting has been formed. By the same applied potential, the fluctuation range of EN and energy density of the substrate was small in comparison with the weld, indicating that the passivation film of the weld had a poor re-healing ability and was prone to be attacked. Due to that the weld had higher energy density, therefore, on which pitting developed faster than on the substrate.

Corrosion behavior of Mo, prepared by plasma activation sintering technique, in molten LiF-LiCl-LiBr-Li at 500 ℃ was examined by means of immersion test, XRD, FE-SEM and EDS. The results show that the sinttered Mo have good corrosion resistance in LiF-LiCl-LiBr molten salt, but it will be corroded by residual impurities forming corrosion products of MoO₂ and MoS₂. Furthermore, the addition of metallic Li into the molten salt will induce the grain boundary corrosion of Mo, where rich in O element, thereby lead to separation of Mo grains and severe corrosion of Mo. Meanwhile, the corrosion products changed from MoO₂ to Li₂CO₃.

The oxidation behavior of a rare earth containing heat-resistant Mg-alloy Mg-14Gd-2.3Zn-Zr was studied in air for 20 h at 200 and 300 ℃, and for 50 min at 440 ℃, respectively. The surface morphology and phase composition of the oxide scales were characterized by means of XRD, SEM and EDS. The results show that the formed oxide scales were mainly composed of MgO. As the oxidation temperature increases, beneath the oxide scale, the Gd content in the surface of the substrate gradually increased. Of particular note is the formation of an intermediate layer of continuous and dense Gd₂O₃ in between the oxide scale and substrate, which can prevent the further consumption of Mg²⁺ in the substrate alloy, thereby increasing the oxidation resistance of the Mg-alloy.

Zr₅₅Cu₃₀Al₁₀Ni₅ amorphous alloy with high energy state and high free volume content was prepared by twin-roll rolling method. Then the effect of structural stability on the electrochemical properties of the prepared amorphous alloy in 3.5% (mass fraction) NaCl solution was studied. The results show that the free volume of the annealed alloy is smaller than that of the as-cast one, while the former one suffered from pitting corrosion during the potentiodynamic polarization test. The size and number of the electrochemical corrosion test induced corrosion pits are reduced on the surface of the alloy annealed in vacuum at 653 K (lower than T_g) for 30 min. The size of corrosion pits become smaller and the number of pits increases for the alloy annealed at 693 and 723 K (between T_g and T_x) respectively. The nano-crystallites formed in the amorphous alloy may increase its pitting sensitivity, the decrease of free volume in the matrix may hinder the further propagation of corrosion pits. This study shows that the amorphous alloy strip with high energy and high free volume content prepared by Twin-roll rolling method is prone to suffer from corrosion, whereas, the annealing below the crystallization temperature can reduce its free volume content and thus improve its corrosion performance.

Nitrogen-free carbon nanoparticles (CNPs) were prepared by thermal decomposition method with citric acid as carbon source. While nitrogen-doped carbon nanoparticles (N-CNPs) were prepared by thermal decomposition method with citric acid as carbon source and urea as nitrogen source. The above nano-particles were characterized by means of atomic force microscope, infrared spectroscope and Raman spectroscope, and their corrosion inhibition performance for Q235 steel in 1 mol/L HCl solution was comparatively studied by mass loss method, electrochemical means and laser confocal scanning microscope. The results showed that the two carbon nanoparticles belonged to mixed-type corrosion inhibitors, the corrosion inhibition efficiency of N-free carbon nanoparticles was 37.5%, and the corrosion inhibition efficiency of the carbon nanoparticles was significantly improved after being doped with N. The corrosion inhibition efficiency of N-CNPs reached 90.96%.

A super-hydrophobic surface is constructed on the Cu substrate by chemical etching, high-temperature oxidation and then modifying with 1-Dodecanethiol as hydrophobic agent, in order to improve the corrosion resistance of the Cu substrate. The results show that when chemical etching for 8 min, high temperature oxidation for 6 h, and 1-Dodecanethiol modification for 15 min, a net-like layered structure with sufficient roughness can form on the Cu surface, which can capture a large amount of air. At this time, the surface of the Cu substrate has the best hydrophobicity with a contact angle of 165.50° for water. The measured potentiodynamic polarization curve shows that in comparison with the bare Cu, the corrosion rate of the superhydrophobic surface is significantly reduced, and the corrosion current density drops from 7.43×10^-5 A·cm^-2 to 4.31×10^-6 A·cm^-2. The results of electrochemical impedance spectroscopy showed that the charge transfer resistance of the superhydrophobic surface was significantly higher than that of the bare Cu substrate, indicating that its corrosion resistance was obviously improved due to the presence of the superhydrophobic surface film. Compared with the current methods for preparing superhydrophobic surfaces, this method is cheaper, simpler and environmentally friendly.

The effect of surface roughness and scratch depth on corrosion behavior of 304 stainless steel beneath droplets of solution (0.5 mol/L NaCl+0.25 mol/L MgCl₂) were studied by means of electrochemical method and the surface analysis techniques. It was found that the increase of roughness and scratch depth can significantly enhance the probability and shorten the induction time of pitting corrosion. The corrosion pits are shallow disk-shaped and the size of pits increases with the roughness and scratch depth. According to the distribution checking, the corrosion pits tend to distribute randomly on the surface of low roughness or no scratches, while they tend to appear at the scratches near the edge of the droplet on the surface of high roughness with deep scratches. According to the element distribution in the pitting region, it was found that the pitting corrosion was related to the evaporation of liquid droplets and the increase of Cl^- concentration, which led to the destruction of important components of the passivation film such as oxides of Fe and Ni.

The hydrogen embrittlement susceptibility of DP780 steel under different strain rates (10^-4, 10^-5 and 10^-6 s^-1) was studied by means of slow strain rate tensile test and electrocheminal hydrogen pre-charging. The results showed that the hydrogen embrittlement susceptibility increased with decreasing strain rate, while the decreasing increment of the hydrogen embritttlement susceptibility was related to the hydrogen pre-charging parameters. When the pre-charging current density was low, pre-charged hydrogen content was low and there was no hydrogen-induced cracks in the steel. More hydrogen atoms could diffuse to the center of sample with the decreasing strain rate, which led to the increasing width of brittle region in fracture surface center portion and hydrogen embrittlement susceptibility of the steel. However, when the pre-charging hydrogen current density was over 30 mA/cm², pre-charged hydrogen content increased to 8.5 mg/L and the initial hydrogen-induced cracks generated in the steel could act as hydrogen traps, which could influence the inward diffusion and aggregation of hydrogen, therewith induce hydrogen embrittlement as a result of capturing hydrogen atom. Therefore, the hydrogen embrittlement sensitivity of the steel decreases with the increase of strain rate.

The effect of Zr addition of 0%, 0.2%, 0.4% and 0.6% (mass fraction) respectively on the microstructure and corrosion behavior in simulated body fluid of Mg-2Y-1Zn alloys is systematically investigated via XRD, OM, SEM and EDS, as well as hydrogen evolution measurement and electrochemical measurement. The results show that Mg-2Y-1Zn is mainly composed of α-Mg and Mg₃Y₂Zn₃ phases, and the addition of Zr (≤0.4%) does not change the type of the second phase, while Zr can effectively refine the grains, optimize the microstructure, slower the corrosion current density, improve the corrosion resistance of the alloy, and make the alloy tend to uniform corrosion. However, when the addition of Zr is 0.6%, the excess Zr will precipitate to form a Zr rich region, which promotes the occurrence of galvanic corrosion and reduces the corrosion resistance of the alloy. The results of hydrogen evolution measurement show that the Mg-2Y-1Zn-0.4Zr alloy has the best corrosion resistance.

The effect of ultrasonic impact on corrosion fatigue properties of P355NL1 steel welded joints was studied, while the surface morphology and the fractured surface were characterized by optical microscope and scanning electron microscope. Meanwhile, the electrochemical corrosion rate of the weld joints before and after ultrasonic impact was comparatively examined by electrochemical workstation. The results show that the fatigue strength of the welded joint in the as welded state decreases by 12.5% in 6% (mass fraction) NaCl corrosion solution in comparison with that of the substrate. In 6%NaCl solution and water, the fatigue strength of the ultrasonic impacted welded joints is increased by 75% and 53%, and the slope of S-N curve is changed by 75.4% and 60.4%, respectively, in comparison with that in the welded state. The maximum depth of the plastic deformation layer is about 350 μm. The fatigue life of the welded joints is significantly improved by the ultrasonic impact, correspondingly, the fatigue fracture location is also transferred from the weld toe to the weld or base metal area, and the number of corrosion pits is significantly reduced. The results clearly show that the ultrasonic impact can refine grain, reduce stress concentration, eliminate harmful residual tensile stress, introduce beneficial residual compressive stress, reduce electrochemical corrosion rate, and improve the corrosion fatigue performance of welded joints of P355NL1 steel.

Corrosion behavior of a pipeline steel in an artificial soil in the presence of dynamic AC interference, as a simulation of the interference of high-speed railway, is studied by means of mass-loss method, electrochemical measurements and surface analysis technique. The results show that, in the presence of dynamic AC interference, cathodic protection potential shifts to the negative direction, while the AC interference can increase the cathodic protection current density of the pipeline steel coupon. With the increase of interference intensity, the corrosion degree of pipeline steel increases and the pits deepen obviously. Cathodic protection (CP) can significantly slow down the corrosion degree of pipeline samples induced by the AC interference, and the corrosion rate is reduced to half of that of samples without cathodic protection. In the precent experimental case, the applied potential -1.0 V CP can fully protect the pipeline steel from corrosion induced by the dynamic AC interference with stray current below 100 A/m².

The composite emulsion of ethyl orthosilicate (TEOS) and isobutyltriethoxysilane (IBTS) was prepared by a sol-gel method. The TEOS/IBTS composite coating was applied on concrete surface, which then was placed on the marine tidal zone to experience biofouling process. The results show that the TEOS/IBTS composite coating provides a long-term hydrophobic effect on the concrete surface. Hence, it is difficult for marine microorganisms to adhere on the TEOS/IBTS composite coated concrete surface, thereby, the formation of a microbial membrane may be retarded. High-throughput DNA sequencing results show that the application of the TEOS/IBTS composite coating reduced the species richness and community diversity of microorganisms on the concrete surface. In particular, the abundance levels of Desulfobacterota and Firmicutes, which are prone to cause concrete corrosion, were significantly reduced. Furthermore, the bacterial community structure on concrete surface was improved. CLSM and SEM results show that the TEOS/IBTS composite coating improved the surface morphology and characteristics of the concrete, thereby reduced the fouling degree of the concrete in marine environment.

The corrosion behavior of 316L stainless steel in an artificial oilfield wastewater at different temperatures was studied by potentiodynamic polarization measurement and SEM analysis. At the same time, the point defect model (PDM) was used to explain the pitting corrosion behavior of stainless steel. The results show that as the temperature of the oilfield wastewater increases, the pitting sensitivity increases and the pitting potential decreases for the 316L stainless steel. The experimental results of the pitting potential and the square root of the potential scanning rate at different temperatures were analyzed by PDM. The PDM combined with the competitive adsorption theory and the formation mechanism of cation vacancies at the passive film/solution interface can successfully explain the results of this paper.

The corrosion behavior of A572Gr.65 steel in various artificial soil solutions was studied by means of electrochemical workstation, scanning electron microscopy (SEM), X-ray diffractometer (XRD) and other techniques. The results show that with the increase of pH value, the polarization resistance of A572Gr.65 steel also increases, meanwhile the free-corrosion potential of A572Gr.65 steel moves positively, while the free-corrosion current density decreases. The corrosion resistance of steel in alkaline solution is the best. When the solution is acidic, the main corrosion product is γ-FeOOH. High concentration of H⁺ can promote the generation of impedance arc and destroy the passive film on the surface of A572Gr.65 steel. In addition, H⁺ will generate hydrogen in the reaction process, make corrosion products loose, and accelerate the corrosion process. In this process, the hydrogen evolution reaction of cathode is the controlling step for the whole process. When the pH value becomes neutral or alkaline gradually, OH^- will promote the transformation of γ-FeOOH to dense Fe₃O₄ and α-FeOOH. The dense corrosion products will hinder the diffusion of corrosive ions and dissolved oxygen, protect the substrate effectively and slow down the progress of corrosion. In this process, the formation of corrosion active points on the metal surface and the dissolution rate of anode are the controlling step for the whole process.

Composite of polyaniline nanofiber/modified graphene oxide (PANI-F/CTGO) was synthesized by in-situ copolymerization in a non-hydrochloric acid medium. PANI-F/CTGO was introduced into waterborne epoxy polymer emulsion (WEP) as an anti-corrosion component to form composite coatings. The anticorrosion effect of the composite coating on stainless steel was assessed by means of salt spray test, electrochemical method, Fourier transform infrared spectroscope, SEM and XRD. Results show that the chemical bonding between PANI-F and CTGO improved the dispersion and compatibility of PANI-F/CTGO in epoxy emulsion. PANI nanofibers prepared in non-hydrochloric acid medium is conducive to better corrosion resistance of the coating due to that there is no corrosive HCl was involved into the prepared coating. PANI-F/CTGO/WEP coatings showed high open circuit potential and impedance modulus in 3.5%NaCl solution after salt spray test for 240 h, indicating their excellent corrosion protection performance. Meanwhile, the mechanism of synergism of active passivation and physical barrier of PANI-F/CTGO was revealed.

The fatigue crack growth rate of marine engineering structural steel DH36Z35 in air and artificial seawater are comparatively assessed by means of a home-made seawater corrosion fatigue machine by applied stress ratio of 0.1, 0.3 and 0.5 with a frequency of 3 Hz. The results show that the fatigue crack growth rate increases with the increase of stress ratio R under the same ΔK bothin air and artificial seawater, and this phenomenon is especially evident in the near threshold range 1×10^-7 mm/cycle≤da/dN≤1×10^-6 mm/cycle. When the fatigue crack growth rate (da/dN) is above 1×10^-6 mm/cycle, a flection point may emerge on the curve of fatigue crack growth rate measured both in air and seawater. For the case of testing in the seawater, above the flection point the crack growth is accelerated, whereas below which the crack growth is inhibited. The higher the stress ratio is, the higher the fatigue crack rate corresponding to the inflection point is. Based on the difference of test results in air and artificial seawater by different stress ratio and threshold, a modified Walker model for the prediction of corrosion fatigue crack growth rate is established. By the new prediction model, the fatigue crack growth rate by the applied different stress ratio in seawater can be predicted through the fatigue crack growth rate in air.

Large non-metallic inclusions and their effect on the hydrogen induced cracking behavior (HIC) of the X65 acid-resistant pipeline steel were investigated by means of metallography and scanning electron microscopy (SEM). While the maximum size of non-metallic inclusions in the steels of different volume was predicted by extreme value statistics (SEV). According to the predicted inclusion of large size, the possible hydrogen induced cracks (HICs) evoked by the large inclusions were estimated for the X65 pipeline steel. The results show that the large non-metallic inclusions in X65 pipeline steel increase with the increase of the steel volume, and the predicted maximum inclusion size is consistent with the results of metallographic observation. The estimated size of HICs evoked by the inclusion of predicted maximum size is consistent with the crack length detected by HIC test of X65 pipeline steel.