Corrosion of 1.4110 stainless steel at nitrate acid at 323 K

Abstract

Abstract. Corrosion is a common process of destroying construction materials. The material during these processes loses its properties, it causes deterioration of functions, loses its usefulness, applicability. One of the important aggressive environments in the agricultural industry is nitrogen, from which nitric acid may be formed. Due to high hardness and also a good resistance to abrasion and corrosion the 1.4110 steel is commonly used in industry as knife blades, machining tools, measuring tools, pump construction, valves. Stainless steel is steel with good resistance to homogeneous or local environmental attack. The aim of the research was to determine the corrosive wear of 1.4110 steel (X55Cr), corrosion resistance with martensitic microstructure using the Huey test. The tested steel contains 0.52 % C, 13.4 % Cr and 0.65 % Mo. The samples were weighed before start of the corrosion processes and after them. Samples were kept in nitric acid 65 % at temperature 323K. The holding times of the samples in nitric acid were 48, 96, 144, 192, 240, 288, 336, 384 hours. The percentage of mass losses was determined by the weight method. Each sample was examined metallographically using an optical microscope and the surface roughness test using a profilometer. The test results were analyzed in order to determine the corrosion rate of steel in mm/year and g/m2 as well as percentage mass loss and determine the corrosion resistance in this environment. After corrosion of the steel, the roughness has increased. Mass loss and corrosion velocity were presented by a linear function, but greater accuracy is obtained by using the 3rd degree polynomial. Then it was confirmed that as the holding time in boiling nitric acid increases, corrosive wear increases. Generally, the tested steel 1.4110 has a good corrosion resistance in the nitricacid environment.Keywords: steel, stainless steel, corrosion, corrosion rate, roughness. IntroductionIn technics corrosion mainly concerns metal materials and within them also iron alloys. Stainless steel is steel with good resistance to homogeneous or local environmental attack. Corrosion-resistant steels created have resistance only in specific conditions [1][2][3][4][5][6][7]. Their corrosion resistance depends i.a. on the chemical ingredients, microstructure, surface condition. Corrosion-resistant steels have at least 10.5 % chromium and a maximum of 1.2 % carbon, elements that conduce to forming of the surface layer (passive), with dense structure and consistent with the base, causing a jump of the chemical potential, it has a tendency to self-rebuilding and provides corrosion resistance. Along with the increasing content of the chromium, nickel, molybdenum the corrosion resistance is gaining. Corrosion is a phenomenon of material damage as a result of the chemical and electrochemical environment influence [8][9][10][11][12].In alloys and metals changes occur as a result of interaction with the surrounding environment. The corrosion process begins at the point of contact with the environme...