Chapter VI includes a wide range of microstructure description of steels (carbon steels: K55, N80-1, highly alloyed H13 and stainless steel 316) and composites (GRE — Glassfibre Reinforced Epoxy and HDPE — High-Density Polyethylene), and its influence on their corrosion resistance, leading to elaboration of the database of materials used in the shale gas production system due to their kinetics of degradation. In this Chapter, the modern methods within the study of electrochemical and mechanical properties of selected materials were used. The mechanism and kinetics of corrosion and erosion degradation were measured using electrochemical DC methods (LPR, LSV, potentiostatic and galvanostatic), AC methods — electrochemical impedance spectroscopy (EIS), gravimetric methods and morphological studies of material degradation with the use of image analysis. The composition and structure of corrosion products were investigated by XRD technique, FTIR spectroscopy, and SEM followed by EDS analysis. The Authors focused on four main tasks, the first one included the description of research on the corrosive-erosive wear resistance of steel and composite materials in the crevice fluid and the second comprised of the research on the corrosion resistance of steel and composite materials in the H2O-CO2-H2S atmosphere. The third part of the results presented in this chapter related to the microbiological corrosion resistance SRB (Sulfate Reducing Bacteria) of steel and composite materials in the H2O-CO2-H2S atmosphere. An important part of the investigations described in Chapter 6 was to make the comparison of the corrosive behaviour of steels, which are in frequent use in the shale-gas production system, and composites under the neutral salt spray conditions. Based on the above mentioned experiments, the authors compiled an extensive data- base, where a broad description of corrosion resistance of materials for shale-gas production systems is included. The matching of microstructural features with corrosion resistance and mechanical properties of various types of steel and new generation composite materials would have a strong influence on future experiments conducted in such a common aspect in the shale-gas production system, as materials degradation is.