Failure analysis was carried out on recuperator tubes which carry water recovering waste heat of burnt mixed gas. The fins used on the tubes to protect the tubes are martensitic stainless conformed by analysis. The deposit on the surface of the tube conformed to be rich in sulfur. The sulfur at high temperature reacts with metals during the sulfidation reaction. Sulfidation is a chemical reaction of a solid substance, such as a metal or an alloy, with sulfur in some form in its working environment. This produces compounds of sulfur that usually form on the solid surface or under the surface of the substance, such as a metal or alloy. Sulfidation can occur on exposure of metals to temperatures above approximately 200 °C in gases containing Hydrogen and Sulfur at partial pressures greater than 10 atm. The root cause of failure is found to be sulfidation which is due to the sulfur containing gas where sulfur attacks the metal at high temperature producing a compound on the surface. The tubes’ metal sulfides form at faster rates than metal oxides, have low melting points and can result in scale spallation. In the remedial action it is suggested not to use steels with less than 20% Cr as it increase the risk of sulfidation. Use of grades such as 310 SS instead of 316L can giver better life to the tubes due to more resistance to sulfidation. Ferritic stainless steel AISI 446 with adequate thickness may be another cheaper steel that can be used. Minimizing sulfur content by introducing flue gas -De-sulfurization before recuperation can also avoid such failure of the tubes.