This paper describes three case studies in the Gas & Refining Industry in which some corrosion and fouling problems were detected. In these cases the failures were a result of an inappropriate material selection during Engineering Design. A common factor was identified: failure occurred in a very short operating time. Economical maintenance and even safety issues were consequences of the failures. The first case was a corrosion problem in the 316L filters installed in four Fire-seawater pumps. They were located at the Jetty of an LNG Terminal and the failure occurred after one year and a half of operation. The second case documents a leak produced in a Spent Caustic Treatment Reactor (Alloy 20) after 6 months in service. And the third case addresses fouling problems (after a few days of operation) in a sodium hypochlorite dosing pump. Crystals were generated when sodium hypochlorite got in contact with the Alloy 20 material. For each case the root failure causes and the new material proposal is described. KEYWORDS: Material Selection corrosion failure fouling Alloy 20 316L seawater sodium hypochlorite.