Tsyrulnyk O. Creation the electrochemical methods for a diagnostics of the technical state of structural steels after long-term operation in corrosion-hydrogenating environments

Structural steels for main oil and gas pipelines, oil storage tanks, pipes of drilling columns and reactor pressure vessels in the energy and petrochemical industries. To develop the electrochemical methods of diagnostic the technical state of long-term exploited structural steels based on approximation dependencies between informative electrochemical and mechanical characteristics sensitive to their operational degradation, with a further prediction of their resistance to corrosion and corrosion-mechanical fracture and to develop nondestructive methods of a diagnostic conservative values of the informative parameters of corrosion-mechanical failure of high ductile steels at an expertise of emergency destruction. The research methods were electrochemical methods of a study kinetic of corrosion process and hydrogen permeation through metal membrane, an amount of hydrogen occluded by metal determining by vacuum extraction; mechanical test for determining strength and plasticity (in air and in corrosive-hydrogenation environments), impact toughness, static and cyclic crack resistance, corrosion crack resistance, resistance of corrosion-erosion fracture and hydrogen embrittlement. The new informative parameter for estimation of the steels resistance to corrosion macrodefects growth such as oxidation charge of the deformed surface is proposed. Based on it the electrochemical methods for diagnostic of the corrosion-mechanical fracture characteristics of steels are developed. The informative electrochemical parameters of operational degradation of the metal are proposed and the criteria for choosing of the corrosive environment for their evaluation are justified. The new electrochemical methods of diagnostic operational degradation of the mechanical properties of pipelines steels are developed on the basis of established approximation dependencies by non-destructive testing of their electrochemical characteristics. The developed method of complex diagnostics of the exploited metal state and residual lifetime of main pipelines is implemented on DK "Ukrtransgaz" and used to determine the residual lifetime of the main gas pipelines (in particular, the section "Urengoy - Pomary - Uzhgorod"), as well as UMG " Prykarpattransgas " to create a database relating to mechanical and electrochemical characteristics of the exploited steels, to determine the residual lifetime and for the feasibility study of the necessity to restructure pipeline sections. Developed methods for diagnostics of operational degradation of the steels for their sensitivity to brittle macrocracking is implemented at the enterprise "Remtehmorport" (Odessa) for estimating the operational degradation of steels for portal cranes. The using field is pipeline transportation, port and bridge metal structures, reactor pressure vessels in the energy and petrochemical sectors.