Коррозия под изоляцией как один из факторов сокращения срока службы промышленных трубопроводов

Abstract

The effect of porosity type and residual number of water-soluble chloride ions of insulation material on the under-insulation corrosion rate in industrial pipelines is considered. For the research, standard test methods were used in accordance with current Russian and foreign regulatory and technical documentation. The dependences of the corrosion rate and the damage area of carbon steel on the structure (porosity) of the thermal insulation material (open, semi-closed, closed), the residual number of water-soluble chloride ions and water-repellent agent is established. The residual life of a carbon steel pipeline was calculated at a critical depth of pitting corrosion under a thermal insulation layer of various materials. The types of thermal insulation materials characterised with lowest under-insulation corrosion rate are determined. The maximum 0.29–0.41 mm/year corrosion rate of carbon steel under materials with open porosity was 0.53–1.8 times lower than under comparable materials with closed porosity. An increased corrosion rate is determined to be directly proportional to an increase in the number of chlorine anions in the structure of the material. The smallest area of steel surface corrosion damage is observed under materials with open porosity. Among the materials examined, the requirements of the current regulatory standards are met by materials of the stone wool group having a low chloride content and basalt super thin fibre. The longest remaining service life (11 years) of a carbon steel pipeline at hdef= 5.87 mm critical depth of pitting corrosion is obtained under a rock wool layer having a low chloride content.