Comprehensive Analysis of Bitumen-Mastic Coatings on Steel Underground Distribution Gas Pipelines. Part 1. Characteristics of the Coatings Used and the General Mechanism of Structural Degradation of Bitumen Materials

In accordance with the Concept of the National Strategy for Sustainable Development of the Republic of Belarus for the period up to 2035, the main objective in the gas sector is to maintain production assets at a level that ensures safe energy supply. The basis of these production assets are gas distribution networks, directly gas pipelines. It is known that the factor that poses the greatest threat to the technical condition of steel underground gas distribution pipelines is corrosion. To compensate for the global corrosion factor, steel underground gas pipelines are equipped with special anticorrosive agents, including protective insulating coatings. Bitumen-mastic insulating coatings (BMIC) are the most common coatings in the domestic gas distribution system, which were used earlier than others in industrial practice for corrosion protection. The article provides a comprehensive analysis of BMIC in terms of their design, materials used, and the evolution of coatings from bitumen-mineral to bitumen-rubber and further to bitumen-polymer. A brief overview of the development of theoretical provisions on the structure, physico-chemical properties and component composition of bitumen is presented. The general mechanism of structural degradation of bituminous materials is shown, characterized by a gradual increase in internal stresses, increased viscosity, and brittleness, leading to complete and irreversible destruction. Depending on the temperature conditions and the associated intensity of oxidative processes, autooxidation (low-temperature, low-intensity) and thermal (high-temperature, intensive) oxidation of bitumen hydrocarbon compounds are distinguished. The place of autooxidation and thermal oxidation at the pre-operational (technological) and operational stages of the life cycle of bitumen materials is shown, as well as the influence of temperature effects on the coating material at the technological stage, manifested in an increase in the heterogeneity of the initial state of the coating before its operation.