Study of electrochemical properties of austenitic chromium-nickel steel 12Kh18N10T in concentrated sulfuric acid

Abstract

Considerable attention has always been paid to the issues of protection against chemical corrosion of technological equipment operating in aggressive environments, and even now this issue does not lose its relevance. Recovery of absorption heat is an integral part of the process of minimizing energy costs, and that is why special requirements are imposed on the quality and service life of heat exchange units. Within the framework of the work done, the electrochemical behavior of austenitic nickel-containing steel grade 12Kh18N10T (equivalent of AISI 304), used for the manufacture of process equipment for sulfuric acid production processes by the double contact -double absorption method, was studied. For the studied sample of austenitic nickel-containing steel, anodic potentiodynamic polarization curves were obtained, on which two weakly manifested passivation regions were noted. It has been established that the predominant contribution to metal losses is made by chemical corrosion, while during the operation of steel structures, iron is leached from the surface layer with formation of a protective nanofilm. Thickness of the resulting protective film is 35 nm or more, with the exposure time of steel in hot sulfuric acid for 200 hours. Increasing of the exposure time does not significantly affect the thickness or composition of the protective coating. Using X-ray phase analysis, it was established that the protective film is based on nickel and chromium compounds. The corrosion rate of equipment in the presence of a protective film does not exceed 0.1 mm/year, there are no pitting and intergranular corrosion. The data obtained will allow not only predicting and planning repair and maintenance work, but also organizing a corrosion prevention system without introducing additional reagents into the system.