Hydrogen in welds and its affect on performance from the perspective of cracking and embrittlement of steels has been widely studied, and welding procedures have been developed to minimize the deleterious effects of hydrogen. The practical problem is whether hydrogen outgassing from welds causes damage to FBE and liquid epoxy coatings on pipelines. FBE coatings on longitudinal welds made at pipe mills have developed defects because of hydrogen outgassing. Field welds are often coated shortly after welding, inspected and either buried or submerged, and there is a greater chance for more hydrogen...
Hydrogen in welds and its affect on performance from the perspective of cracking and embrittlement of steels has been widely studied, and welding procedures have been developed to minimize the deleterious effects of hydrogen. The practical problem is whether hydrogen outgassing from welds causes damage to FBE and liquid epoxy coatings on pipelines. FBE coatings on longitudinal welds made at pipe mills have developed defects because of hydrogen outgassing. Field welds are often coated shortly after welding, inspected and either buried or submerged, and there is a greater chance for more hydrogen in the field welds than mill welds. If coating damage occurred by outgassing, the damage could go undetected and affect the pipeline corrosion control. The objectives were to examine hydrogen outgassing as a cause of damage to FBE and liquid epoxy coatings, to collect and contrast experience with hydrogen in longitudinal welds and circumferential welds, to quantify hydrogen pickup and release from steel pipe and welds. Methods and practices are identified to avoid damage to FBE and liquid epoxy pipeline coatings from hydrogen outgassing. The approach was to examine epoxy coatings applied over welds for damage from hydrogen outgassing and to conduct experiments to determine the amount and rate of hydrogen desorption (outgassing) from welds. The effects of hydrogen desorption on coatings was examined for commercial FBE and liquid epoxy coatings along with screening tests with liquid glycerol and clear epoxy. Hydrogen desorption was measured directly on welds, and a model was developed to describe the outgassing of diffusible hydrogen and the amount of diffusible hydrogen remaining in the weld.