Hredil M. Estimation of corrosion-hydrogen degradation of gas trunk line steels after its long term service

The corrosion-hydrogen degradation of gas trunk line steels. Aim - to investigate the corrosion mechanism of gas trunk line pipes' internal surface, to establish the general regularities of properties' degradation in- bulk of pipe wall and to clarify the role of transported medium in the degradation processes. Methods - gravimetry, polarization method, vacuum extraction, hydrogen permeation, mechanical tests, SEM fractography. Results - the corrosion mechanism of gas trunk line pipes' internal surface in the model brine is established. Hydrogen evolution is shown to result from the corrosion processes inside the pipe and to create danger of in-bulk steel hydrogenation. Substantial deterioration of corrosion and corrosion-mechanical properties of gas pipelines, especially polarization resistance and crack growth resistance, is revealed after its service for 28-40 years. The recommendations are given to the Management of main gas pipelines "Prykarpattransgas" for substantiation of reliable and safe operation mode of main gas pipelines after its long term service. Field of use - gas-transport sector.