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This study was conducted with a high level of thoroughness. X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM) were used to analyze the phase composition and microstructure of the AM-2024Al and the RO-2024Al. The hardness and porosity of the AM-2024Al, as well as the bonding strength between AM-2024Al and RO-2024Al, were also investigated. Furthermore, the corrosion and tribocorrosion properties and failure mechanisms of the AM-2024Al and the RO-2024Al were systematically and thoroughly compared and analyzed. The results of this comprehensive study revealed that the AM-2024Al displayed a similar phase structure and higher hardness in comparison to the RO-2024Al, and the AM-2024Al was compact and tightly bound to the RO-2024Al with a bonding strength of over 55.5 MPa. Furthermore, the AM-2024Al exhibited better corrosion resistance under PDP (potentiodynamic polarization) corrosion and similar wet sliding wear resistance under an approximate pure friction process (OCP corrosion, namely open circuit potential corrosion) and tribocorrosion compared with the RO-2024Al. These findings provide a high level of confidence in the potential of cold spraying additive manufacture 2024Al as a reliable way to repair damaged RO-2024Al. [Display omitted] • The tribocorrosion is first reported for the CS additive manufacturing 2024Al alloy. • The AM-2024Al exhibits superior anti-corrosion compared to the RO-2024Al. • The AM-2024Al has a comparable tribocorrosion resistance to the RO-2024Al. • Splats (AM-2024Al) and grains (RO-2024Al) are partly peeled during the tribocorrosion. • A plastic deformation layer was generated in the wear track surfaces of the two 2024Al. [ABSTRACT FROM AUTHOR]

• Electrochemical dissolution models of TiAl 45XD in NaNO 3 and NaCl are proposed. • The surface integrity of TiAl 45XD in NaNO 3 is better than that in NaCl solution. • The polarization behavior of TiAl 45XD is quite different in NaNO 3 and NaCl. • The ηω-j curves show an unusual dissolution behavior of TiAl 45XD. • Corrosion morphology of TiAl 45XD in NaNO 3 and NaCl are different. Electrochemical machining is an effective method for the processing of Ti-45Al-2Mn-2Nb+0.8 vol% TiB 2 XD (or TiAl 45XD) alloys due to the absence of tool wear and the high material removal rate. This study investigated the electrochemical dissolution behavior of TiAl 45XD in NaNO 3 and NaCl solutions, explaining the unique phenomena during the dissolution. The polarization curves, open-circuit potentials and material removal rate (ηω-j curves) were measured. It is found that the lamellar colonies are fully exposed after the electrochemical polarization in NaCl solution and that only some insoluble TiB 2 disperse on the specimen surface in NaNO 3 solution. The ηω-j curves reveal an unusual dissolution behavior of TiAl 45XD. Dissolution experiments were then carried out at different current densities and corrosion times. The corroded specimens were examined and analyzed using a surface-finish measuring instrument, scanning electron microscope and energy-dispersive X-ray spectroscopy. The results indicate that the surface quality is higher in NaNO 3 solution than in NaCl solution because the specimen surface suffers from the pitting and severe localized corrosion and then forms many micro-protrusions in NaCl solution. It is also found that the micro-protrusion plays an important role in the electrochemical dissolution behavior of TiAl 45XD. Finally, qualitative models for the electrochemical dissolution behavior of TiAl 45XD in NaNO 3 and NaCl solutions were proposed. [ABSTRACT FROM AUTHOR]

Corrosion processes of SiC-CaAl 12 O 19 (CA 6) composite refractory were carried out by both static crucible test and rotary drum test at 1500 °C and 1600 °C under a reducing atmosphere, respectively. The corrosion mechanism of the SiC-CA 6 refractory was analyzed by means of X-ray diffraction(XRD) and scanning electron microscope(SEM). The results show that the corrosion temperature and condition had significant influence on the slag resistance of the SiC-CA 6 refractory. But no matter which corrosion methods and which temperatures under the condition of this experiment, the SiC-CA 6 refractory exhibited good penetration resistance even though a little corrosion appeared at a higher temperature. During the corrosion process, most of Fe containing oxide in slag could be reduced by CO in atmosphere and SiC in samples to form Fe-Si metal alloys, which precipitated at the interface between the slag and composites. The penetrated slag could react with the SiO 2 produced by SiC oxidation and the CA 6 matrix to form CaAl 2 Si 2 O 8 and corundum, filling the pore inside the samples and causing the densification of the reaction layer. Because of the reaction between infiltrated slag and SiC-CA 6 refractory, the composition and properties of local slag changed and inhibited the further penetration. • High temperature corrosion processes of SiC-CaAl 12 O 19 (CA 6) composite refractory were carried out. • The corrosion mechanism of the SiC-CA 6 refractory was analyzed at evaluated experiment conditions. • The corrosion resistance of SiC-CA 6 refractory was compared with the traditional high chromia refractory. [ABSTRACT FROM AUTHOR]

Highlights: [•] Delayed and immediate crevice corrosions are investigated. [•] The crevice corrosion morphologies are studied by SEM. [•] The relocation of active dissolution region is observed. [•] The mechanisms of crevice corrosion are discussed in detail. [ABSTRACT FROM AUTHOR]

Formation of profuse I 2 -type solute-enriched stacking faults (SESFs) in fine grains and transformation of SESFs to 18R-long period stacking ordered (LPSO) phase are attained in Mg-Er-Zn-Zr alloys. It is first confirmed by scanning Kelvin probe force microscopy (SKPFM) that SESFs with nanostructure act as weak anodes and the 18R-LPSO phase serves as cathode, which are verified by the theoretical calculated electronic work function and observation of scanning transmission electron microscope. Furthermore, the preferential corrosion of uniformly dispersed SESFs is demonstrated to be conducive to forming effective passivation film. It provides a new insight for developing high-strength and anti-corrosion Mg alloys. [Display omitted] • The PD of weak anode SFs is measured at the nanoscale by SKPFM for the first time. • The reliability of SKPFM results is verified by the theoretical calculated WF. • Preferential corrosion of SFs is demonstrated using STEM-EDS for the first time. • Preferential corrosion of solute-enriched SFs is conducive to formation of passivation film. • A new insight for designing high-strength and anti-corrosion Mg alloys is proposed. [ABSTRACT FROM AUTHOR]

Abstract: The inhibition effect of glycine (Gly) towards the corrosion of low alloy steel ASTM A213 grade T22 boiler steel was studied in aerated stagnant 0.50M HCl solutions in the temperature range 20–60°C using potentiodynamic polarization (Tafel polarization and linear polarization) and impedance techniques, complemented with scanning electron microscope (SEM) and energy dispersive X-ray (EDX). Electrochemical frequency modulation (EFM), a non-destructive corrosion measurement technique that can directly give values of corrosion current without prior knowledge of Tafel constants, is also presented here. Experimental corrosion rates determined by the Tafel extrapolation method are compared with corrosion rates obtained by electrochemical, namely EFM technique, and chemical (i.e., non-electrochemical) method for steel in HCl. The chemical method of confirmation of the corrosion rates involved determination of the dissolved cation, using ICP-AES (inductively coupled plasma atomic emission spectrometry) method of analysis. Corrosion rates (in mm y−1) obtained from the electrochemical (Tafel extrapolation and EFM) and the chemical method, ICP, are in a good agreement. Polarization studies have shown that Gly is a good “green”, mixed-type inhibitor with cathodic predominance. The inhibition process was attributed to the formation of an adsorbed film on the metal surface that protects the metal against corrosive agents. Scanning electron microscopy (SEM) and energy dispersion X-ray (EDX) examinations of the electrode surface confirmed the existence of such an adsorbed film. The inhibition efficiency increases with increase in Gly concentration, while it decreases with solution temperature. Temkin isotherm is successfully applied to describe the adsorption process. Thermodynamic functions for the adsorption process were determined. [Copyright &y& Elsevier]

Abstract: The electropolishing behavior of the Inconel 718 alloy was studied by using rotating disc electrode (RDE) in the HClO4–CH3COOH mixed acids with different HClO4-concentrations. After electropolishing, surface morphologies of RDE specimens were examined with surface profiler, atomic force microscope and scanning electron microscope. According to the surface morphologies observed, three types of anodic dissolution behavior can be characterized in relation to the HClO4-content in mixed acids; namely, leveling without brightening of the surface in the mixed acids with 10 and 20vol% HClO4, leveling and brightening of the surface in the mixed acids with 30 and 40vol% HClO4, and a matt and gray surface in the mixed acids with 50vol% or more HClO4. Anodic dissolution in the first and second dissolution types follows a mass-transfer controlled mechanism, in which a linear relationship between the reciprocal of limiting-current density and the reciprocal of square root of rotating speed of RDE specimen can be detected. Owing to precipitation of salt film on the polished surface of the Inconel 718 material, saturated dissolved metallic ions could be the chemical species for the mass-controlled mechanism. The salt film, in addition, could enhance the corrosion resistance of the Inconel 718 alloy. [Copyright &y& Elsevier]

The potential of low-voltage, high-resolution scanning and scanning transmission electron microscopy (SEM/STEM) for morphological characterization of various surface insulating films on aluminium and its alloys has been assessed by examination of porous anodic films, barrier anodic films and corrosion product layers. The characterization shows clearly the value of the approaches, particularly the ability to image directly fine details of appropriately-prepared aluminium surfaces that have usually required examination by transmission electron microscopy (TEM). Such ready characterization assists mechanistic understanding of the contributions of the macroscopic surface and flaws or second phase to the filming and corrosion processes. Further, the approaches are applicable to other materials where such understanding was limited by the sample preparation routes available for TEM. [Copyright &y& Elsevier]

• A comparatively considerable corrosion resistance is achieved in extruded Mg-3Zn-11Gd-0.6Zr alloy. • Lower potential differences between Mg-Zn-Gd ternary phases and Mg matrix are beneficial to corrosion behavior. • A wide distribution of compact X-phase lamella acts as corrosion barrier during corrosion. • X-phase could act as an anode during micro-galvanic corrosion with W-phase. The corrosion behavior and mechanism of as-cast and as-extruded Mg-Zn-Gd-Zr alloys with specific ternary phases are investigated using scanning electron microscope (SEM), scanning Kelvin probe force microscope (SKPFM), immersion and electrochemical tests. Lamellar X-Mg 12 GdZn, net-like W-Mg 3 Gd 2 Zn 3 and strip-like I-Mg 3 Zn 6 Gd phases form successively. The eutectic W-phase owns the highest potential difference of 120 mV with Mg matrix, accelerating micro-galvanic corrosion. Continuously distributed and undersized I-phase leads to uniform corrosion. The as-extruded Mg-3Zn-11Gd-0.6 Zr alloy exhibits superior corrosion resistance, due to the relatively low potential difference between X-phase and matrix, the corrosion barrier effect and typical {0002} <10−10> texture components. [ABSTRACT FROM AUTHOR]