NATURALLY-OCCURRING ORGANIC-SUBSTANCES AS CORROSION-INHIBITORS FOR MILD-STEEL IN ACID-MEDIUM - CONCENTRATION AND TEMPERATURE EFFECTS

Potentiodynamic cathodic and anodic polarization technique was used to study the effect of some common amino acids concentration on the corr osion inhibition of mild steel in H2SO4. A value of 1.0 x 10(-4) M rep resents a critical concentration, for the aliphatic amino acids, above which the corrosion rate increases. The increase of the sulphur-conta ining amino acids concentration largely decreases the corrosion rate. A mono-layer adsorption of the amino acid molecules on the metal surfa ce was proposed with the adsorption behaviour following the Temkin iso therm at 30 degrees C. The effect of temperature on the corrosion inhi bition of amino acids was also studied over the temperature range 25 t o 60 degrees C. Values of the apparent activation energy in the range of 42-49 kJ mol(-1) were estimated for the steel corrosion in the inhi bited acid solutions.