Investigation of Cyclohexylidenecyclohexanon Steel Corrosion Inhibitor as Surfactant

A modified organic waste of the caprolactam production is investigated by electrochemical impedance spectroscopy technique as a corrosion inhibitor of carbon steel in 20% hydrochloric solution. It is shown that cyclohexylidenecyclohexanon is a basic inhibiting component in such inhibitor. The inhibitor is investigated also as surfactant at the solution -air interface by means of the maximum bubble pressure technique. It is shown that the Langmuir adsorption of inhibitor takes place at solution -air and solution -steel interfaces. Equilibrium adsorption constant values make (1.7 +/- 0.4) x10(3) M-1 and (4.0 +/- 0.8) x10(3) M-1 respectively. Free adsorption energy was estimated as (-28 +/- 0.5) kJ mol(-1) and (30 +/- 0.6) kJ mol(-1) respectively. The closeness of the adsorption constant and the free adsorption energy values suggest that the inhibitor adsorption on steel is caused basically by the hydrophobic interaction of inhibitor molecules with the solution molecules and less depends on the interaction with steel.