لخّصلي

Abstract The corrosion inhibition of aluminium in HCl solution in the presence of exudate gum from Raphia hookeri at temperature range of 30-608C was studied using weight loss and thermometric techniques.It has been shown that natural products of plant origin contain different organic compounds (e.g. alkaloids, tannins, pigments, organic and amino acids, and most are known to have inhibitive action [8-15].The inhibition efficiency increases with increase in inhibitor concentration butdecreaseswithanincreaseintemperature.TheinhibitiveeffectoftheRaphiahookeriexudatecouldbeattributed to thepresenceofsomephytochemicalconstituentsintheexudatewhichisadsorbedonthesurfaceofthealuminium metal.The exudate gumwasfoundtoobeyTemkinadsorptionisothermandKinetic-ThermodynamicModelofElAwadyetal.atalltheconcentrationsandtemperaturesstudied.Phenomenonofphysicaladsorptionisproposedfrom the activation parameters obtained.Keywords: Aluminium; Raphia hookeri; Inhibition; Corrosion; Hydrochloric acid; Exudate gum 1.Thermodynamic parameters reveal that the adsorption process is spontaneous.

Abstract The corrosion inhibition of aluminium in HCl solution in the presence of exudate gum from Raphia hookeri at temperature range of 30–608C was studied using weight loss and thermometric techniques. The exudate gum acts as an inhibitor in the acid environment. The inhibition efficiency increases with increase in inhibitor concentration butdecreaseswithanincreaseintemperature.TheinhibitiveeffectoftheRaphiahookeriexudatecouldbeattributed to thepresenceofsomephytochemicalconstituentsintheexudatewhichisadsorbedonthesurfaceofthealuminium metal. The exudate gumwasfoundtoobeyTemkinadsorptionisothermandKinetic–ThermodynamicModelofElAwadyetal.atalltheconcentrationsandtemperaturesstudied.Phenomenonofphysicaladsorptionisproposedfrom the activation parameters obtained. Thermodynamic parameters reveal that the adsorption process is spontaneous. Keywords: Aluminium; Raphia hookeri; Inhibition; Corrosion; Hydrochloric acid; Exudate gum 1. Introduction Corrosion inhibitors are widely used in industry to reduce the corrosion rate of metals and alloys in contact with aggressive environment. Most of the corrosion inhibitors are synthetic chemicals, expensive and very hazardous to environment. Therefore, it is desirable to *Corresponding author. source for environmentally safe inhibitors [17]. It has been shown that natural products of plant origin contain different organic compounds (e.g. alkaloids, tannins, pigments, organic and amino acids, and most are known to have inhibitive action [8–15]. Other authors have also shown that the inhibitive effect of some plants solution extract is due to the adsorption of molecules of phytochemicals present in the plant on the surface of the metal [16–19], which blocks the metal surface 0011-9164/09/$– See front matter 2009 Elsevier B.V. All rights reserved. doi: 10.1016/j.desal.0000.00.000