Conversion Electron Mössbauer Spectrometric Study of Corrosion Products of Iron Immersed in Sodium Chloride Solution

The corrosion products of iron formed in 3% sodium chloride solution under various conditions of temperature, pH values of the solution, concentrations of dissolved oxygen, and durations of immersion were analyzed by conversion electron Mössbauer spectrometry (CEMS) at room and dry ice temperatures (297 and 200 K), paying particular attention to β-FeOOH formation in aqueous media. Although γ-FeOOH was a major product of iron corrosion in sodium chloride solution containing 5 to 6 ppm dissolved oxygen in the temperature range of 18 to 45 C, it was found that β-FeOOH could be formed on the iron surface under the special conditions of pH 6 to 8, 0.5 to 1 ppm concentration of dissolved oxygen and higher temperature. The mechanism of the β-FeOOH formation in sodium chloride solution is discussed.