Material compatibility is key to proper equipment design, operation and reliability in both well and artificial lift completion. This paper addresses material compatibility lessons learned from well completion components exposed to harsh hydrocarbon and saline subsurface environments. Dismantle Inspection Failure Analysis (DIFA) was utilized to ascertain the failure root cause for 25 water source wells utilizing Electrical Submersible Pumps (ESPs). Positive Material Identification (PMI) testing was used to identify the cause of 17 of the failed completions — incompatible material selection resulting in completion workover after an average of 562 days of production. Moreover, X-ray Power Diffraction (XRD) and Energy Dispersed Spectroscopy (EDS) analysis were used to characterize deposit samples from the pulled equipment. It was discovered, upon pulling of the failed completions, the tubular pup joint above the ESP pump discharge head contained holes due to corrosion. From the various analysis and tests, it was determined the pup joint (a 7″ tubular) was made of carbon steel while the ESP was made of super duplex steel. Laboratory analysis further proved these two metal materials were not compatible in the harsh high chloride environment, which resulted in galvanized corrosion of the pup-joint above the pump discharge head. Galvanic corrosion is an electrochemical process in which one metal corrodes preferentially to another when both metals are in electrical contact in the presence of an electrolyte. A geochemical analysis of the water from these wells indicated a high concentration of aggressive species including elevated Total Dissolved Solids (TDS), chloride, sulphate and carbonate. The composition is considered highly conductive and highly corrosive to bare carbon steel. Energizing of the ESP power cable provided the electro-magnetic field that aided migration of electrons across the carbon steel of the tubular pup joint and the duplex stainless steel of the pump discharge head. A guideline for selecting two dissimilar metals based on the volts differential across the metals and higher grades of tubular materials were recommended for such a harsh environment. A guideline for selecting dissimilar metals for compatibility — based on the lessons learned from the ESP completions and the recommendations made to improve runlife of ESP completions in harsh high-chloride environment — is presented in this paper. The recommended approach was applied in recompleting the failed and pulled 25 ESP completions utilizing L80 modified 13-chrome and Glass Reinforced Epoxy (GRE) lined tubular according to the guideline work detailed in the paper.