MASoud /gwg Repair welding of Aus S.S exposed to hydrogen partial pressures and high temperature is possible and success is achieved in both hydrogen removal before repair welding and in successful repair welding. We have done with success at tube sheets of high pressure exchangers in hydrogen service in fertilizer plants - lined with S.S over medium low alloy steel exposed to high hydrogen partial pressures and high temperatures and seen service life of > 25000 hours. Repair welding procedure needs careful approach. So also hydrogen removal from tube sheets lined with S.S. For specific cases, if plant personnel do not have experience, taking the help of outside consultants experienced in this would help. It is not an imponderable task to repair weld SS with exposure to hydrogen and driving away hydrogen also is also not an imponderable task. Only those who had done with success and care would need to be consulted. Hope this helps C.V.Srinivasan Nishi Engineers Pvt Ltd India June 7, 2008 E-mail: nishi@vsnl.com >The problem regarding hydrogen in austenitic stainless steel >is the delta ferrite content. The interface region between >austenite and delta ferrite and even carbide precipitation >will exhibit a high probability of hydrogen damage. >Unfortunately, because the solubility of hydrogen is higher >in austenite than ferrite and with the hydrogen diffusivity >in austenite being low, in comparison to ferrite, removal of >hydrogen would be difficult prior to weld repair.