Determination of concentration of diffusible hydrogen in pipeline steels: comparison between degassing and desorption methods

This research work investigates the hydrogen uptake in a pipeline API 5L grade X65 carbon steel, through electrochemical cathodic charging method. It is studied a solution that representing typical pH values of waters present in soils and it is compared with a reference environment. Additionally, it is examined the cathodic polarisation effect on the electrochemical charging process. Hydrogen content was measured via two different methods: the first one by thermal degassing employing Leco analyser and the second one, using an electrochemical desorption method, by anodic polarization. The results of these two strategies of measure were compared to estimate total and diffusible hydrogen concentration respectively. It shown that in condition of normal cathodic protection, the diffusible hydrogen concentration is negligible. The concentration of diffusible hydrogen in the higher case, it is less than 1/3 about of the total concentration and it decreases rapidly