Polyaspartic acid, a polymeric form of aspartic acid has been examined as a corrosion inhibitor for steel as a function of pH, temperature, and hydrodynamic conditions. The temperature ranged from 25°C to 95°C and the concentration ranged from less than 1 % to about 10 % by weight. Experimental procedures included electrochemical impedance spectroscopy, the rotating cylinder electrode, and coupon immersion. At low to neutral pH values, polyaspartic acid increases the corrosion rate of steel. At high pH above about 10, polyaspartic acid is a reasonably robust corrosion inhibitor. Between a pH of 7 and 10, corrosion in the presence of polyaspartic acid is a complex function of temperature, concentration, water quality, and hydrodynamic conditions. By combining corrosion potential measurements with speciation diagrams as obtained by titration, a reasonably cohesive explanation of the behavior has been developed.

Subject
Acids, Water, Polyaspartates, Corrosion rate, Titration, Impedance, Iron, Acidity, Constants, Corrosion inhibitors, Steel, Corrosion potential, Hydrogen
Keywords:
polyaspartic acid, corrosion, inhibition, steel, iron, rotating cylinder electrode, electrochemical impedance spectroscopy, immersion test, polarization resistance, water treatment
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1995
Association for Materials Protection and Performance (AMPP)
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