Characterization of the corrosive action of mineral waters from thermal sources: A case study at Azores archipelago, Portugal

Waters from natural sources of the São Miguel Island in the Azores archipelago have been investigated regarding their corrosive action on metallic materials. The corrosive and encrusting characteristics of the waters have been established in terms of relevant chemical parameters (namely pH, conductivity, total dissolved solids (TDS), and concentrations of bicarbonate, calcium, magnesium, chloride, and sulfate ions) and their temperature by using Langelier, Ryznar, Puckorius and Larson-Skold indexes. The validity of this methodology has been tested by measuring the corrosion rates of various metals exposed to various waters using electrochemical methods. The materials of industrial interest under investigation were carbon and galvanized steel, zinc, 304 and 316L grade stainless steels, brass, and Cr-Ni alloys. The greater aggressiveness of these waters was found for the less noble materials, and they experienced high corrosion rates