Composite coatings of Zr/CrAlSiN composed of multi-elements and multi-layers were fabricated by multi-arc ion plating technique. The coatings Zr/[Al(Si)N/CrN] with stratified structure were obtained by the combination of alternatively depositing selected targe materials on substrates and intermittently moving substrates close to specific targets. Then their mechanical property, friction, and wear performance in the absence of corrosion, corrosion performance in the absence of friction and wear, and corrosion-wear performance in artificial seawater, were systematically investigated. The results showed that the prepared coatings with the desired stratified structure could inhibit the growth defects and even repair the formed defects of the coatings obviously. With the increase of thickness ratio of the CrAlSiN layer, the best comprehensive mechanical property of the Zr/[Al(Si)N/CrN] coating would achieve, when the modulation ratio is 1:6. Since the CrAlSiN layer is also of a multilayered Al(Si)N/CrN structure, thus increasing the thickness ratio of the CrAlSiN layer may result in the increment of lateral interface of the composite coating, thereby improving the barrier effect of the coating in the corrosive environment. Accordingly, the increase in the thickness ratio of the CrAlSiN layer could improve either the corrosion resistance in the absence of friction and wear or the corrosion resistance of the coating, while friction was activated, and further reduced the mutual promotion of corrosion and wear. When the modulation ratio was 1:6 and 1:8, the Zr/[Al (Si) N/CrN] coating exhibited better anti-corrosion and wear properties in the artificial seawater.

The synergistic inhibition effect of forestry and agricultural residue of walnut green husk extract (WGHE) and the anionic surfactant of SLS on the corrosion of cold rolled steel (CRS) in 2.0 mol/L H₃PO₄ solution was studied by mass loss measurement, electrochemical technique and surface analysis methods. The results show that individual WGHE or SLS exhibits moderate inhibition capacity with the maximum inhibition efficiency of c.a. 50% for a dosage of 100 mg/L at 50 ℃. However, incorporation of WGHE with SLS can obtain better inhibitive performance, and the maximum inhibition efficiency (η_w) can reach as high as 95.3%. There is a strong synergistic inhibition effect for WGHE and SLS. The synergism parameter increases with the increase of temperature in general. WGHE/SLS can more efficiently retard both cathodic and anodic reactions simultaneously. Nyquist spectrum exhibits a depressed capacitive loop, and the charge transfer resistance follows the order: WGHE/SLS＞WGHE＞SLS. SEM and AFM micrographs confirm that WGHE/SLS can efficiently alleviate the corrosion degree of steel surface in phosphoric acid media. There is a synergism between SLS with any one of the major components such as rutin, quercetin and 1-methylnaphoqinone in WGHE respectively, but their synergistic inhibition is all below that of the complex WGHE/SLS.

The characteristics and mechanisms of elemental sulfur induced corrosion of P110SS sulfur-resistant steel in wet flow carbon dioxide atmosphere of various flux and relative humidity at different temperatures were investigated by means of X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), in terms of the composition and morphology of the corrosion product and the substrate steel. The results show that the elemental sulfur does not corrode P110SS at 60 ℃ in the wet flow CO₂ with 30% relative humidity, however when the relative humidity reaches to 60% or higher, the elemental sulfur may participate in the cathodic reaction to generate S^2-, which in turn combines with Fe²⁺ to produce FeS. As the temperature reaches to 80 ℃, the elemental sulfur becomes more active and may react with the steel to form FeS even in the flow CO₂ with 30% relative humidity. When the relative humidity reaches to 60% or higher at 80 ℃, the elemental sulfur starts to hydrolyze, generating H₂SO₄ and H₂S, which aggravates the corrosion of the steel. Furthermore, when the CO₂ flux with high humidity at high temperature, FeS will also catalyze the hydrolysis of the elemental sulfur to form more SO₄^2- and S^2-. Finally, the thickness of the corrosion product increases with the increasing humidity and the density of the corrosion product decreases with the increasing temperature. Therefore, the findings of this study can provide a reference for the prevention and control of the elemental sulfur corrosion of sulfur-resistant steels.

The anodic oxidized 5056 aluminum foil is post sealed with titanate modified silane coupling agent by dip coating method. The effect of solute ratio, dipping duration, drying time and temperature on the foil corrosion resistance is systematically studied. The mechanism related with the enhancement of corrosion resistance induced by the titanate additives is discussed. The results show that a continuous and dense composite film is formed on the surface of anodic coating after sealing with the titanate modified silane coupling agent. The film thickness is uniform on both surfaces of the aluminum foil. The best corrosion resistance is achieved with a composite film formed in the sealing bath with the ratio of Ti to Si=0.3 to 5.7. The coating after sealing exhibits 30 min before the occurrence of coating damage by K₂Cr₂O₇ solution drop testing at 19 ℃, free-corrosion current density of 7.42 nA/cm², and salt spray test up to 16 d, being higher than those of the single silane coating of 9 min, 1.81×10² nA/cm², and 8 d, respectively. This is attributed to the spatial network structure of the composite film formed by the titanate stereo framework and the silane additives. This develops dense film on the anodic coatings to retard the corrosive species, and thus promotes the corrosion resistance.

Zr- and/or Ti-based chemical conversion coating (ZrTiCC) is an important and representative chromium-free surface modification technology for Al-alloys and Mg-alloys. ZrTiCC has reached the maturity of final commercial utilization in industry. The design concept to improve the performance of ZrTiCC was proposed based on the deposition mechanism analysis of conventional ZrTiCC in this paper. Moreover, the design concept was applied on the 5083 Al-alloy and AZ91D Mg-alloy. The results indicated that both the corrosion resistance of the coated substrates and the adhesion property with organic coating were significantly improved. Finally, the key factors affecting the performance of ZrTiCC were analyzed and the future development trend was expected.

A new F-class marine low-temperature steel plate was firstly pre-corroded to form different oxide scales. Then their reciprocating friction behavior was characterized by means of white light interferometer and scanning electron microscope in terms of the microstructure and wear morphology of the worn steel samples. The results show that the corrosion resistance of the steel samples with γ-FeOOH oxide scale, the original steel samples, and the steel samples with Fe₃O₄ oxide scale become higher in turn. Among them, the steel sample with the dense and complete Fe₃O₄ oxide scale has the lowest amount of wear, the wear scar profile is the shallowest and narrowest, and the surface is dominated by adhesive abrasion, and the corrosion resistance is also the best; the γ-FeOOH oxide scale on the steels is relatively loose with smallest friction coefficient, but the amount of wear is the largest by the coupling of friction and corrosion; the wear mechanism of the steels with the two oxide scales is mainly abrasive wear, and the surface of the untreated steel presents more furrows and pits.

In this work, the corrosion behavior of marine engineering materials in three typical harsh marine atmospheric environments is investigated i.e., the so called "Antarctic low-temperature and high-irradiation ice-snow freezing-melting environment", "high-temperature, high-humidity and high-salt fog atmospheric environment of South China Sea", and "coastal chlorine-haze coupling environment". The results show that in Antarctic environment, the electrochemical corrosion process can occur even beneath the cover of snow and ice at extremely low temperature. The freezing-melting process of ice and snow leads to the existence of surface electrolyte film for a long period, which promotes the corrosion reactions and accelerates the localized corrosion. In the environment of the South China Sea, there is a synergistic effect of chemical oxidation and electrochemical corrosion on the surface of non-ferrous materials in high humidity and high Cl^- atmospheric environment at high temperature. Different aluminum alloys have different corrosion initiation and propagation driving forces (i.e., diffusion and charge transfer, hydrogen-induced intergranular cracking, and wedging effect of corrosion products). The synergistic effect of time of wetness (TOW) and Cl^- content lead to the deviation of corrosion dynamics from the power function. In the coastal chlorine-haze coupling environment, the key controlling factor of NH₄⁺ in acceleration of corrosion in the chlorine-haze environment is the continuous supply of H⁺ caused by the buffering effect of NH₄⁺. Meanwhile,“quasi auto-catalytic pitting” corrosion occurs because of the synergistic effect of Cl^-, NO₃^-, and NH₄⁺.

The enamel/aluminide composite coating on Ni-based superalloy GH4169 is prepared by two-step process i.e, pack cementation and subsequent spray/fired enamel coating. The coating mainly consists of three layers: the outer layer of enamel coating (40 μm), and the middle layer of aluminide coating mainly composed of Ni₂Al₃ phase (~20 μm), and the inner layer of an interdiffusion zone of about 3 μm in thickness. The corrosion behavior of enamel/aluminide composite coating/GH4169, aluminide coating/GH4169 and blank GH4169 alloy respectively were investigated beneath NaCl deposits in atmosphere of oxygen flow carrying water vapor. The results show that the oxidation and chlorination of elements Fe and Cr in the aluminide coating and alloy can autocatalytically ocurr due to the presence of synergistic reaction of NaCl with water vapor, thereby the oxide scale on the surface is seriously damaged. The enamel coating could isolate the corrosive media such as NaCl and water vapor from the aluminide coating/GH4169, thus blocking the oxidation-chlorination autocatalytic reaction, thereby, the corrosion of the aluminide coating/alloy is retarded.

The galvanic corrosion behavior of 9XX low-alloy steel, 316L stainless steel and Al-Mg 5083-H116 alloy in a simulated 3000-meter deep sea environment was studied by means of observation of macroscopic morphology, 3D confocal microscope, and scanning electron microscope. The results show that the galvanic corrosion tendency between 9XX low-alloy steel and 316L stainless steel is relatively high, and the corrosion is more serious. The potential difference between 5083 alloy and 316L stainless steel is large, but the corrosion of 5083 alloy coupled with 316L stainless steel is relatively light because of the formation of dense protective film on the surface of two alloys; 316L stainless steel exhibits excellent corrosion resistance due to the formation of protective oxide film on the surface.

The difference in the corrosion resistance between the as-cast and heat treated equiatomic CoCrFeMnNi high entropy alloy (HEA) and hot rolled X80 and X100 pipeline steels in a simulated alkaline soil solution was investigated by immersion test, electrochemical tests, XPS and AFM. The results show that the high entropy alloy exhibits the characteristics of local corrosion, and few pits are sporadically distributed on its surface, while X80 and X100 pipeline steels display the characteristics of severe general corrosion, with large size corrosion pits. Moreover, the passive film of HEA is compact and stable, and contains more Cr oxide, bound water and less FeO, which is conducive to increasing its corrosion resistance, whereas the passive film of pipeline steel is thinner and defective, and has poor protective ability. The corrosion resistance of the HEA before and after heat treatment is all better than those of X80 and X100 pipeline steels, and the corrosion resistance of the HEA can be further improved by heat treatment.

High chemical activity leads to rapid corrosion for Mg-alloys in aqueous solution, which restricts its wide range of applications. As one of the most widely used anti-corrosion means, corrosion inhibitor has shown high efficiency and low cost, which can greatly improve the corrosion resistance of Mg-alloys in industrial applications. Based on the chemical composition of inhibitors, the research progress of inorganic, organic and compound corrosion inhibitors was reviewed in this paper. The inhibition mechanism and future research direction of corrosion inhibitors for Mg-alloys were also proposed.

With the expansion of high-speed train operation area and the extension of service duration, corrosion has become an important factor threatening the safety and reliability of trains. Based on electrochemical principle and 4G wireless communication technology, a novel intelligent corrosion monitoring system for structural materials of high-speed train was developed. It was installed on a high-speed train traveling between Beijing and Guangzhou, as well as in three out-door exposure test stations in Wenchang, Wuhan, and Qingdao as a menas to perform comparatively examination of material corrosion. The 6-month continuous corrosion data of an Al-alloy and protective coating of high-speed train car-body, as well as those in the above test stations was collected and analyzed. The data provides important support for predicting the corrosion risk of vehicle structural materials, which is in favor of evaluating the life attenuation of coating and strengthening the safety management of the whole life cycle of high-speed train.

In this article, the research progress of atmospheric corrosion test methods is reviewed, namely atmospheric corrosion accelerating test method, atmospheric corrosion electrochemical test method and atmospheric corrosion monitoring and detecting technology. Among the atmospheric corrosion acceleration test methods, the multi-factor cyclic corrosion test has become the main development direction of simulated atmospheric corrosion acceleration tests. At the same time, due to the improvement of the spatial resolution, the electrochemical test methods for atmospheric corrosion have also been extended from macroscopic electrochemical technology to micro-area electrochemical technology. In addition, with the development of the Internet of Things and computer technology, modern data processing technology based on data mining and machine learning has also been applied in atmospheric corrosion monitoring and testing technology.

The corrosion of ceramic furnace electrode materials in molten glass is discussed from three aspects: material, temperature and applied current. The results show that Inconel 693 forms an Al₂O₃ scale in molten glass. The corrosion resistance of Inconel 693 is better than that of Inconel 690. With the change of temperature, the corrosion rate of the material is determined by the Cr diffusion rate inside the material and the Cr₂O₃ dissolution rate on the surface. In the presence of electric current, the passive film of Inconel alloy in molten glass is destroyed and its corrosion resistance becomes poor. It is also suggested that the corrosion behavior and the relevant corrosion mechanism of materials should be investigated in combination with the practical operation conditions of JHM in the future.

Due to the poor compatibility between montmorillonite and organic-inorganic hybrid sol-gel system, APTES (aminopropyltriethoxysilane) was used to graft-modification of montmorillonite (AP-MMT) . Through the introduction of amino group on the surface of montmorillonite to establish a tough bonding with the sol-gel system, a more compact and stable composite coating was obtained on AZ31B Mg-alloy. The characterization of montmorillonite indicated that APTES were successfully grafted onto the montmorillonite lamellae. Analysis results showed that the corrosion resistance of sol-gel coating with AP-MMT was improved to a certain extent compared with that of pure sol-gel coating. Electrochemical impedance spectroscopy (EIS) analysis of coated samples immersing in 0.05 mol/L NaCl solution for different time showed that the sol-gel coating before and after doping with AP-MMT exhibited different failure mechanism, which were related to the denser structure caused by the addition of modified montmorillonite.

The corrosion behavior of 6063 Al-alloy in ethylene glycol and propylene glycol antifreeze (typical concentration is 20%) in the simulated operating conditions of the valve cooling system i.e., at 50 ℃ by applied 10 mA DC current, was comparatively studied by means of immersion test with mass loss measurement and electrochemical test, as well as SEM with EDS, XRD and AFM. The results showed that: the corrosion behavior of 6063 Al-alloy in ethylene glycol solution and propylene glycol solution was comparable. The corrosion rate of 6063 Al-alloy increased slowly and then rapidly with the increase of immersion time. The overall corrosion rate of 6063 Al-alloy in propylene glycol was lower than that in ethylene glycol. Electrochemical analysis results showed that with the increased of immersion time, the interface capacitance increased, the polarization resistance decreased and the free-corrosion current density increased, but the free-corrosion current density of 6063 Al-alloy in propylene glycol was always lower than that of ethylene glycol. SEM observation revealed that there were obvious pits on the surface of the samples in the two antifreeze solutions, but the number of pits was significantly less in the propylene glycol. EDS results showed that the corrosion products composed mainly of Al and O with a little C, indicating that the two antifreeze solutions and their corresponding oxidation products were involved in the corrosion process of Al-alloy. The results of AFM showed that the corrosion product film on 6063 Al-alloy formed in propylene glycol was much compact with higher corrosion resistance, which was consistent with the results of SEM. In summary, propylene glycol with lower toxicity was less corrosive than ethylene glycol, so that could be used as an alternative antifreeze for valve cooling system.

The deposition of corrosion product Fe₃O₄ on the steam generator heat exchange tubes and supporting tube sheets is one of the main causes of corrosion accidents in the secondary circuit of nuclear power plants. Adding a dispersant can reduce the amount of corrosion product deposition. In this paper, polyacrylic acid (PAA) is selected as the dispersant, and its dispersion effect on Fe₃O₄ was examined in water with different concentration ratios of PAA to Fe₃O₄ (0, 0.01, 0.1, 1, 10) at ambient temperature for 0 and 24 h respectively. Then the effect of PAA on the dispersion characteristics of Fe₃O₄ was assessed via coupon test with a simulated secondary loop operating condition (autoclave), as well as the corresponding oxide scale formed on carbon steel was characterized by means of SEM with EDS. The results show that the addition of PAA will increase the absolute value of the Zeta potential of Fe₃O₄ and reduce the particle size of the corrosion product Fe₃O₄. PAA has a good dispersing effect on Fe₃O₄, when the concentration ratio of PAA to Fe₃O₄ is 0.1, the dispersion effect is the best. When the Fe₃O₄ concentration ratio is too large, the particle size increases and the dispersion effect decreases. With the increase of PAA concentration (0, 10 and 100 mg/L), the deposited Fe₃O₄ particles_{on the steel surfaceafter tested in autoclave are finer so that the oxide scale on carbon steel coupon was much dense and uniform. As the PAA concentration increases, the C content of oxide scale on carbon steel surface increases, indicating that PAA participates in the surface film formation process. The above results can provide certain theoretical guidance for the application of PAA in the secondary circuit of nuclear power plants.}

The fatigue test for the 7075-T651 Al-alloy samples with and without being immersed in 3.5% (mass fraction) NaCl solution for 150 and 500 h, respectively, was carried out, in order to reveal the influence of corrosion damage on the fatigue behavior of the alloy. The results show that compared to the blank alloy samples, the fatigue life of 7075-T651 Al-alloy subjected to immersion corrosion is significantly reduced due to the presence of corrosion damage. The size of corrosion pits in the specimens immersed for 500 h are much large than those for 150 h, but the fatigue life of the two types of specimens with corrosion damage are more or less at the same stress level. Based on the fatigue notch coefficient theory and Stromeyer three-parameter S-N curve formula, the life of the damaged Al-alloy sample was predicted, and the predicted results totally located in the double dispersion band, which indicates that the predicted formula fits well with the results of experimental results.

The pitting corrosion behavior and mechanism of ferritic stainless steel 439 in various solutions with different concentration of anions Cl^- and HSO₃^- was studied by means of electrochemical test, X-ray diffractometer, X-ray photoelectron spectroscopy, as well as molecular dynamics simulation. Electrochemical test results show that, the corrosion rate of 439 stainless steel will be significantly increased in solutions with simultaneous presence of Cl^- and HSO₃^- rather than that in solutions containing only one of the two anions. The molecular dynamics simulation results show that, compared with solutions containing only one of the two anions, in solutions of the mixed anions the corrosive ions were adsorbed much strongly to the passive film, and their diffusion coefficient is also significantly improved. The corrosion rate of 439 stainless steel in Cl^- containing solutions will gradually increase with the increase of Cl^- concentration, whereas after reaching the critical point, the corrosion rate will gradually decrease. However, when Cl^- and HSO₃^- co-exist in the solution, the corrosion of 439 stainless steel is accelerated.

Magnetic flux leakage internal inspection is the main method for detecting metal damage in oil and gas pipelines. After the magnetic flux leakage testing is implemented, there will exist a residual magnetic field in the pipeline for a long time. The influence of such residual magnetic field on the corrosion behavior of the pipeline steel is not completely clear yet. Therefore, the influence of different magnetic field intensities (0.9, 1.9 and 2.8 kA/m respectively) on the corrosion behavior of X52 pipeline steel in 3.5%NaCl solution was investigated by means of open circuit potential, polarization curves, electrochemical impedance spectroscopy and corrosion morphology observation techniques. The results indicated that the presence of magnetic field can shift negatively the corrosion potential, increased the corrosion current density, reduced the charge transfer resistance, and changed the corrosion morphology to a certain extent. The greater the magnetic field intensity, the greater the influence on the electrochemical corrosion behavior. Through mechanism analysis, it follows that the influence of magnetic field on the electrochemical reaction process may comprehensively be determined by multiple factors such as the magnetic flux intensity near the electrode surface, the magnetic field gradient, the ion-magnetism and -concentration in the electrolyte. The Loren magnetic force can accelerate the diffusion of Fe²⁺ and reduce the thickness of the electric double layer, while the Kelvin force can increase the oxygen content of the electrode interface, all the above factors could promote the corrosion process, the effect of which may be stronger than the corrosion inhibition effect induced by that the Kelvin force causing Fe²⁺ to accumulate on the electrode surface, so that the electrochemical corrosion process was generally promoted.

The corrosion process of the riveted pair of 6A01 Al-alloy-/304 stainless steel-plate was assessed via cyclic salt spray test, aiming especially to clarify the corrosion behavior of the 6A01 Al-alloy, as the main component of the riveted pear. The corrosion kinetics, rust composition and corrosion morphology of the alloy samples were characterized by means of weightlessness method, scanning electron microscope (SEM), energy dispersive spectroscope (EDS), 3D super depth of field microscope and other methods. The results showed that galvanic corrosion and crevice corrosion occurred for the Al-alloy after being riveted onto 304 stainless steel, and its corrosion rate was 8-10 times higher than that of the blank alloy. The variation of corrosion products on the surface of Al-alloy may in turn affect the corrosion process of the Al-alloy. The cracking of the corrosion product can accelerate the corrosion process, whereas, the densification of the corrosion product may be beneficial to its protectiveness.