Scientists have solved the problem of alkali chloride salt destroying the protective layer of materials

Comparison of high temperature KCl corrosion resistance of NiCrAlY and NiCrBSi coatings Courtesy of Anhui University of Technology

Professor Zhang Shihong of the Key Laboratory of Green Preparation and Surface Technology of Advanced Metal Materials of the Ministry of Education of Anhui University of Technology carried out a study on the surface protection of four tubes of biomass power generation boilers, revealing the corrosion mechanism and failure mechanism of coatings in alkaline chlorine environment. Recently, the research results were published in Corrosion Science under the title of “Research on the Thermal Corrosion Behavior of Supersonic Spraying NiCrAlY and NiCrBSi Coatings on 12CrMoV Boiler Steel under 700 ° CKCl Induction”. Liu Xia, a teacher at Anhui University of Technology, and Hu Kai, a doctoral candidate, are the co-first authors of the paper, Zhang Shihong is the corresponding author, and Anhui University of Technology is the first signatory unit.

“Biomass power generation has become an important way to reduce the installed capacity of coal power and achieve the goal of ‘carbon peak- carbon neutrality’, but due to the high content of alkali metals (potassium, sodium, etc.) and chlorine in biomass, alkali metal chloride salts are easy to form during combustion, and the oxides on the surface of commonly used high-chromium alloy coatings will be destroyed due to the formation of alkaline chromate, and in the ‘ In the chlorine active corrosion mechanism, corrosive substances sometimes pass through the oxide layer to cause internal oxidation or chlorination of the coating, which forms a violent corrosion on the boiler pipe and limits the development of supercritical boiler power generation technology with high installed capacity and high heat exchange efficiency. Zhang Shihong said. In view of this, it is very necessary to carry out research on the corrosion properties and mechanism of coatings in alkali chloride corrosive environments, and to develop new coating materials and technologies that are resistant to alkali chloride corrosion.

Zhang Shihong said that in order to solve the problem of alkali chloride destroying the protective layer of the material, the research team used supersonic flame spraying technology to prepare NiCrAlY and NiCrBSi coatings on the surface of the boiler steel, respectively, while improving the corrosion resistance of the boiler steel, explored the oxidation sequence and oxidation mechanism of Cr, Al and Si elements in the high temperature process, and focused on the properties of the oxide film after alkali chlorine corrosion of different phases and structural coatings from the perspective of oxidation thermodynamics and kinetics (such as thickness, continuity, degree of compactness and crystal structure) and the formation, consumption and regeneration mechanisms, revealing the corrosion mechanism and failure mechanism of coatings in alkaline chlorine environments. This research work provides an experimental basis and theoretical basis for the design of protective coatings and other new coatings in this field, and helps to achieve the goals of carbon peaking and carbon neutrality. (Source: China Science Daily Wen Caifei Zheng Cai)

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