Hydrogen interaction and stress-corrosion in hydrocarbon storage vessel and pipeline weldings

This paper addresses important technical problems of H-embrittlement/safety and stress corrosion cracking (SCC) phenomena which can be of concern in various industrial sectors of vessels and pipeline production, including H storage.Intercrystalline and intergranular cracks have been detected in narrow welded zones having particular hardness, gradually rising from little dimensions till crossing all the plate thickness. Such cracks are due to the residual stresses (RS) produced by the construction technique and to the presence of aggressive elements. H+H+ diffusion from sulphured hydrogen molecule toward the ferritic material of the internal surface can produce fissures similar to hydrogen-induced cracking (HIC), especially in the presence of RS. Microanalyses have revealed a sulphur deposit formation in the cracks fracture surfaces, as a presence of H2H2S dragged by LPG fluids. The LPG release due to such cracks in interred vessels near domestic buildings can be dangerous, and an analysis project of its process is under development.