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A structure of {[(Co-DLC)/DLC] X } n Multilayered Nanocomposite Films (MNF) is designed by inserting pure DLC high-resistance layers into Co-DLC nanocomposite film, which consists of alternating Co-DLC and DLC layers were prepared by magnetron sputtering. The electrochemical behavior and magnetic property of the films are modulated by varying the number of deposition cycles (n) and the thickness of one single-cycle (X). The electrochemical results show that this MNF structure significantly improves the corrosion resistance of the films owing to the clear interfaces, which block the micropores penetrating the films. Compared to the co-sputtering film, as the number of cycles n increases to 7, the corrosion resistance is enhanced by one order of magnitude from 2.3 × 104 to 2.2 × 105 Ω·cm2. However, the interfaces between the Co-DLC and DLC layer become blurred when the thickness of one single-cycle X is lower than 30 nm, and the corrosion resistance decreases to 3.7 × 104 Ω·cm2. In terms of magnetism, the multilayer structure helps to regulate the homogeneity of Co particle size. As X increases from 30 to 100 nm, the Co particle size increases from 2.7 to 4.7 nm, and the saturation magnetization intensity (M s) of superparamagnetic property in the films increases from 2.8 to 8.2 mT. As X increases, the remanent magnetization ratio (M r / M s) decreases and reaches 0.011 at X = 100 nm, which is about one order of magnitude smaller than that of the co-sputtering film. This result indicates that the MNF have better superparamagnetic property. It is noteworthy that {[(Co-DLC)/DLC] X } n MNF with X ranging from 100 to 40 nm and n ranging from 3 to 7 can achieve high corrosion resistance and superparamagnetic property, simultaneously. • {[(Co-DLC)/DLC] X } n multilayered nanocomposite films (MNF) are constructed. • Micropores are blocked by multilayer interfaces to improve corrosion resistance. • High anticorrosion and superparamagnetic property are achieved, simultaneously. [ABSTRACT FROM AUTHOR]

Abstract To extend the applications of 316L stainless steel in corrosive environments and correlate the corrosion resistance with composition and microstructure, homogeneous Cr-rich layer with the thickness of 75 μm was fabricated on 316L stainless steel by pack chromizing and post heat treatment. The chromizing layer was mainly composed of Fe Cr solid solution. Post heat treatment eliminated the precipitates and Cr-depletion in the chromizing layer. The corrosion behaviors were studied by electrochemical measurements and corrosion morphology observation. The pitting corrosion in Cl− containing solutions was avoided after chromizing treatment, which was ascribed to the reduced sensitivity of Cr-rich surface to Cl− ions. The higher Cr concentration in the modified layer also improved the long-term stability of corrosion resistance. After immersion in NaCl solution for 24 days, the charge transfer resistance of chromizing sample was higher than that of 316L by a factor of 8.19. In addition, the free corrosion potential shifted to the positive direction after post heat treatment, and the corrosion current density was also reduced to 0.066 μA/cm2. The further improvement on anticorrosion performance was attributed to the homogeneous microstructure. Graphical abstract Unlabelled Image Highlights • The Cr-rich layer was fabricated by high-temperature pack chromizing treatment. • The chromizing layer provided enhanced pitting corrosion resistance for 316L SS. • The correlation between corrosion resistance and composition/microstructure was studied. • Post heat treatment homogenized the microstructure and further improved the performance. [ABSTRACT FROM AUTHOR]

Abstract Zinc phosphate conversion coating was prepared on AZ61 magnesium alloy by using chemical conversion method, and then processed by hydrothermal treatment in solution containing Zn(NO 3) 2 and stearic acid. The surface morphologies, chemical characteristics and wettabilities of multilayer coatings were observed and characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD), Fourier-transform infrared spectrophotometer (FTIR), Raman spectrometer and optical contact angle meter. The corrosion resistance of coatings were determined by polarization curves. Findings show that zinc phosphate conversion coatings on magnesium alloy are in block structure with microcracks and lower corrosion resistance. After hydrothermal treatment, there are few microcracks on the multilayer coating, and the dense ZnO and stearic absorbing layers are grown on conversion coatings with hydrophobic or even superhydrophobic character and higher corrosion resistance. With the increasing of Zn(NO 3) 2 concentration in hydrothermal solution, the water contact angle and corrosion resistance in 3.5 wt% NaCl solution of multilayer coatings are firstly increased and then decreased. The optimum Zn(NO 3) 2 concentration in hydrothermal solution is 0.035 mol/L, which the multilayer coating on magnesium alloy has the highest corrosion resistance with superhydrophobic properties. Based on experimental results, the protection mechanism of multilayer coating is discussed and related with the formation of dense ZnO layer and stearic absorbing layer on magnesium alloy. Highlights • Multilayer coating was fabricated by using phosphating and hydrothermal process. • Zn(NO 3) 2 concentration plays a significant role in the morphology and behavior. • Multilayer coating is composed by phosphating layer and ZnO layer. • Multilayer coating is hydrophobic/superhydrophobic by adsorbing of stearic acid. • Multilayer coating has a higher binding strength and corrosion resistance. [ABSTRACT FROM AUTHOR]

As-cast nickel-aluminum bronze is prone to suffering selective phase corrosion in marine environments. To solve this problem, chromium was introduced via ion implantation to modify its surface microstructure, which was characterized by high-resolution transmission electron microscopy and auger electron spectroscopy. The corrosion behavior was studied by electrochemical measurements and salt spray test. It was found that the inherent selective phase corrosion in as-cast NAB was inhibited effectively when the implantation fluence was 5 × 10 17 ions/cm 2 . The improved corrosion resistance after ion implantation was believed to stem from the rapid formation of a more protective film containing chromium oxides and hydroxides. [ABSTRACT FROM AUTHOR]