Khan et al. Surface Science and Technology (2023) 1:22 https://doi.org/10.1007/s44251-023-00025-2 ORIGINAL ARTICLE Open Access © The Author(s) 2023. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. Surface Science and Technology High-temperature corrosion behavior of bare and NiCr-coated AISI 422 steel by varying the coating thickness in the Na 2 SO 4 + 60%V 2 O 5 environment Niyamat Ullah Khan 1* , S. K. Rajput 1 and Maharshi Yadav 2 Abstract It is difcult to assess fatalities due to high temperature corrosion, such as plant closure time, production loss, decrease in productivity, contamination, etc. In this context, the AISI 422 martensitic steel is a popular choice for high temperature applications due to its unique properties. The durability of this material can be increased by coat- ing technology. The Ni-20Cr composite powder is a highly recommended choice for high-temperature applica- tions. In this research, Ni-20Cr coating was sprayed on AISI 422 steel, using a fame spray process with two diferent thicknesses of 250–350 µm and 350–450 µm. Corrosion studies have been carried out at temperatures of 600 °C and 900 °C for Na 2 SO 4 + 60%V 2 O 5 salt solution environment. The corrosion kinetics were studied with the help of the Wagner equation. Micrographics analysis has been performed by Scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS), and X-ray difraction (XRD) technique. Coated material has been shown better corrosion resistance compared to bare. The low-thickness coating has better corrosion resistance correspond- ing to both bare and high-thickness. Keywords Thermal spray process, Hot corrosion, Martensitic steel, Surface coating, Molten salt 1 Introduction Coal is still the main source of conventional electricity generation. Its usage has increased due to its widespread availability, high demand for electricity, and limitations of unconventional resources [1]. Over the past few decades, coal-fred power plants have played a signifcant contri- bution to the power generation industry [2]. It is a fact that around 42% of global electricity production comes from this source. In this context, the enhancement of the thermal efciency of coal-fred power plants is a matter of research. To achieve this, the working temperature and pressure of steam need to be increased [3]. Usually, the steam passing through the turbine ranges from 250 °C to 375 °C [3, 5]. Te higher efcient steam power plants utilize supercritical steam parameters up to 250 bar and 565 °C temperature [5]. Modern steam power plant uti- lizes ultra-supercritical parameters that work above supercritical [5–7]. An increase in temperature and pres- sure can improve efciency whereas, it can lead to cor- rosion, overheating, solid particle erosion, wear, and premature failure of components such as boiler walls, tubing, and turbine blades [8, 9]. Corrosion is a major concern in steam power plants due to its adverse efect on performance. Te phenom- enon of corrosion occurs when the metal oxidizes and *Correspondence: Niyamat Ullah Khan niyamat20@gmail.com 1 Department of Mechanical Engineering, Bundelkhand Institute of Engineering and Technology, Jhansi, Uttar Pradesh, India 2 Department of Chemical Engineering and Biochemical Engineering, Rajiv Gandhi Institute of Petroleum Technology, Amethi, Uttar Pradesh, India