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To investigate the influence of Mo addition and water vapor content on the high-temperature corrosion resistance of Ni-Al-based coatings, 0Mo, 5Mo, and 10Mo coatings were deposited by APS thermal spray onto stainless steels. The chlorine-induced corrosion test was conducted in an experimental environment simulating a biomass boiler. The results show that adding the Mo element lowers the coating's ability to resist corrosion without water vapor. The coating is more prone to peeling because Mo prevents the coating from eventually forming a protective oxide layer. Water vapor significantly speeds up the production of oxides and modifies their morphology and structure. The combined effects of Mo and water vapor increase the coating's ability to resist corrosion. The development of thick and protective Ni and Al oxide layers on the coated surface is aided by the acceleration of oxide production by water vapor and the alteration of oxide structure by Mo components. [ABSTRACT FROM AUTHOR]

The aircraft serving in the marine environment is easy to cause the corrosion of its structure due to the long-term influence of the harsh environment such as seawater and salt mist. In order to improve the corrosion resistance of aircraft structure, plasma spraying and laser cladding were used to prepare Fe-based amorphous coatings on the surface of 304 stainless steel. The microstructures of the coatings were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), and their microhardness was tested using a Vickers hardness meter. The corrosion behavior of Fe-based amorphous coatings in the simulated seawater environment was studied by potentiodynamic polarization curve measurement and electrochemical impedance spectroscopy. The results showed that the Fe-based amorphous coatings prepared by these two surface technologies have good corrosion resistance, and can reduce the corrosion rate of aircraft structure, so as to ensure the safety of flight operation. [ABSTRACT FROM AUTHOR]

The effect of a nanoalumina sealant treatment on the long-term corrosion behavior of Al-based coatings deposited by flame spraying was investigated. X-ray diffraction and scanning electron microscopy were used to analyze the surface morphology and microstructure of the unsealed and sealed coatings. The long-term ability of the coatings to withstand corrosion was examined by electrochemical corrosion tests and salt spray corrosion experiments. The results indicate that loose pores and microcracks exist on the surface of the as-sprayed Al-based coatings. The morphologies of the surfaces of the sealed Al-based coatings are dense and flat. Electrochemical corrosion results show that the sealing treatment can effectively reduce the density of the corrosion current and improve the impedance values of all coatings. The sealing treatment prevents the corrosion medium from penetrating into the coating because defects such as pores and microcracks are filled with sealant, which can significantly improve the corrosion resistance of Al-based coatings. The corrosion current densities of the sealed coatings after salt spray corrosion tests are higher than those without salt spray corrosion experiments. With increasing salt spray corrosion time, the corrosion current densities of the sealed Al, Al-Mg and Al-Si coatings decrease, while the corrosion current density of the sealed Al-Cu coating rises gradually. The salt spray corrosion results indicate that sealed Al-based coatings are effective for preventing the long-term corrosion of components in marine environments. [ABSTRACT FROM AUTHOR]

Biomass corrosion is a serious problem that affects the reliability and efficiency of biomass boilers. Ni-based coatings are a potential choice to combat biomass corrosion. In this study, the Ni-clad Al coatings were prepared by air plasma spraying, and the coatings were pre-oxidized in an air atmosphere at 700 °C for 6 h. The corrosion resistance of the as-sprayed and pre-oxidized Ni-clad Al coating exposed to KCl was studied at 600 °C for 168 h. The as-sprayed Ni-clad Al coating showed a much higher corrosion rate due to the porous nature of the coating and faster penetration of corrosion products. The pre-oxidation treatment significantly reduced the corrosion rate of the Ni-clad Al coating. The maximum weight gain of the pre-oxidized Ni-clad Al coating was reduced by 23.5% compared to the as-sprayed Ni-clad coating. After pre-oxidation, multiple NiO layers were formed, and voids were significantly reduced. The corrosion products on the surface of the coating changed from nickel-rich oxides to aluminum-rich oxides after the pre-oxidation treatment. [ABSTRACT FROM AUTHOR]

The effects of laser shock processing (LSP) on corrosion behavior of AISI 304 stainless steel in acid chloride solution have been investigated using electrochemical impedance spectroscopy (EIS). Surface modifications including microstructure, residual stress, micro-hardness and phase transformation are characterized. Results show that LSP can promote the formation of deformation twins and deformation induced martensite, produce grain refinement, generate high magnitude compressive residual stress and increase surface micro-hardness. EIS results show that charge transfer resistance of one layer LSP treated sample is always higher than those of double layer LSP treated sample and non-treated sample in both acid chloride solutions, which implies a higher corrosion resistance for one layer LSP due to the formation of the compact passive film with less defects. Grain refinement and compressive residual stress induced by LSP can enhance the corrosion resistance of AISI 304 stainless steel, but the deformation induced martensite generated during LSP decreases the corrosion resistance. Corrosion resistance of AISI 304 stainless steel in acid chloride solution depends on the combined effects of these factors. [ABSTRACT FROM AUTHOR]

The study examined the impact of varying molybdenum content (0 %, 5 %, and 10 % wt) on the high-temperature corrosion resistance of APS-sprayed Ni-clad Al coatings. The coatings were exposed to a simulated biomass-firing environment with pure KCl deposition at 600 °C for 168 h, and a mixed gas containing 15 % water vapor was passed through. The findings revealed that increasing Mo content improved the coating's high-temperature corrosion resistance. The coating with 10 % Mo displayed a continuous layer of Ni and Al oxides on its surface, while KCl was concentrated in the Mo region. Based on the experimental results, a mechanism for how the presence of Mo element contributes to the high-temperature corrosion resistance of NiAl coatings was proposed. [ABSTRACT FROM AUTHOR]