Corrosivity of geothermal brines. Progress report for period ending June 1976

Abstract

Studies carried out during FY 1976 on the corrosivity of ferrous materials in synthetic geothermal brines are described. Electrochemical measurements on the spontaneous corrosion potentials and corrosion rates, and on the kinetics of the anodic and cathodic corrosion reactions of iron and carbon steel were made in 4 M NaCl solution over the pH range from 1 to 11 at temperatures up to 100/sup 0/C in a conventional Pyrex electrochemical cell. A refreshed, stirred titanium autoclave system was designed, constructed, and tested, and will be used for making electrochemical measurements in synthetic brines up to at least 200/sup 0/C. The effect of pH on hydrolysis, precipitation, and electrochemical reactivity of ferrous and ferric ions in 4 M NaCl at 25/sup 0/C was studied, and implications for plant operation are discussed. The pitting potential of type 304 stainless steel in synthetic brine was measured as a function of temperature from 25 to 85/sup 0/C. Plans for research on electrochemical aspects of the corrosion of iron and carbon steel in synthetic geothermal brines during FY1977 are presented. 14 fig. (auth)