Hydrogen charging of carbon and low alloy steel by electrochemical methods

摘要

In the presence of H-2S, metallic materials, such as carbon and low alloy steels, may suffer hydrogen damage and hydrogen embrittlement. Sour service materials must be used in compliance with international accepted standards, used worldwide in oil & gas activities, when fluids are classified as sour. When the temperature is low, the effect of hydrogen on the reduction of toughness and ductility of such materials could be enhanced. Such event might represent a risk for oil and natural gas transporting pipes in low temperature field: in winter time, during the shutdown and the subsequent re-starting operations, they can reach very low temperatures (-40cC) in presence of high H2S content and high pressure. The present study has been carried out in order to set up an electrochemical method to charge two typical pipeline materials (X65 and F22) with hydrogen for mechanical testing at low temperature. The reason of the use of an electrochemical method is to avoid any critical conditions from the point of view of preparation, safety and disposal. Hydrogen content in the specimens was measured by two different methods: hot glycerol bath and LECO hydrogen analyzer. Although the high scattering of the results even when specimens were charged in identical conditions, the results of the two methods are in good agreement. Hydrogen content in the specimens is about 0.6-2 ppm; these specimens were tested by Charpy resilience test and J integral [1].