Degradability of aluminum in acidic and alkaline solutions I. Boukerche a , S. Djerad a,⇑ , L. Benmansour a , L. Tifouti a , K. Saleh b a Laboratoire de Génie de L’Environnement, Département de Génie des Procédés, Université Badji Mokhtar-Annaba, B.P. 12, Annaba 23000, Algeria b Laboratoire de Transformations Intégrées de la Matière Renouvelable (EA 4297), Université de Technologie de Compiègne, B.P. 20529, 60205 Compiègne Cedex, France article info Article history: Received 3 May 2013 Accepted 13 October 2013 Available online 22 October 2013 Keywords: A: Aluminum B: Weight loss B: SEM C: Acid corrosion C: Alkaline corrosion abstract The processes of aluminum degradation in HCl, H 2 SO 4 , HNO 3 and NaOH solutions were investigated in static and agitated media. The effects of concentration, temperature, and mixture of acids were studied. The dissolution of aluminum was faster in NaOH and HCl than in H 2 SO 4 and HNO 3 . The activation ener- gies were 86.5 and 52.4 kJ/mol for Al dissolved in HCl and NaOH respectively. An inhibiting effect on Al dissolution was observed with the mixture HCl + HNO 3 regardless of the conditions used while a syner- getic effect was observed with the mixture H 2 SO 4 + HCl using acids at 4 M. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The natural concentration of metals in the environment has been increased over time by human activities. Some metals such as aluminum, iron and zinc are largely used in domestic as well as in industrial purposes. Aluminum for example is used in cans, food plates, doors, automotive and construction [1]. The increasing severity of the environmental legislations has forced the recycling of aluminum to give a reasonable final destination [2,3]. However, a part is still found in solid waste landfills. The study of the potential release of aluminum when deposited in landfill is of a great impor- tance to predict its long term behavior in nature. In the region of Annaba large amounts of aluminum are present in municipal solid waste. The recycling industry of metals in our region is not yet developed. This is problematic because various reactions can be occurring when aluminum comes into contact with some industrial liquid effluents enough acid or alkaline to initiate the dissolution reactions and pollute the environment [4]. The behavior of alumi- num was extensively studied in the context of corrosion where the research was focused on the protection of the metal from chlo- ride attack [5–8]. Aluminum dissolution was also studied in term of hydrogen production [9–11]. In fact, gaseous hydrogen is consid- ered as an environmentally friendly fuel with high calorific value which can be generated from the corrosion of aluminum in alkaline solutions. Thus, due to its amphoteric character aluminum may be dissolved in acidic or in alkaline solutions. However, only two stud- ies were found in the literature dealing with the comparison of alu- minum dissolution in both environments. Oguzie [12] investigated the inhibiting effect of leaf extracts of Sansevieria Trifasciata on the corrosion of aluminum in 2 M HCl and KOH using the gasometric technique. He found that the organic extract exhibited good inhibi- tion efficiency during Al corrosion in both solutions and that the corrosion of Al in KOH was faster than in HCl. Garcia-Garica et al. [13] studied the effect of nickel on the corrosion of Al and Al alloy AA1050 in HCl and NaOH solutions that are employed in litho- graphic industry. They found that the addition of nickel enhanced the dissolution rate of Al in both solutions. In this study also, the dissolution rate of Al in NaOH was found to be greater than that in HCl. However, the first paper was focused on the protection of aluminum from corrosion and the second one on its acceleration rather than on the comparison of Al dissolution in both environ- ments under the same conditions. In this study a special attention is paid to the kinetic of aluminum dissolution in HCl, H 2 SO 4 , HNO 3 and NaOH under the same experimental conditions. The influence of the operation conditions on the resultant morphology of aluminum was also considered. 2. Experimental methods H 2 SO 4 (96–98%, Biochem), HNO 3 (60%, Cheminova), HCl (37%, Carlo Erba) and NaOH pellets (99%, Biochem) were used as leaching reagents. Al specimens in the form of disc (6 mm of radius, 2.46 mm of thickness and 99.999% purity) were supplied by Sig- ma–Aldrich. The composition of aluminum is given in Table 1. All specimens were used without further polishing but for experi- ments, they were degreased in acetone and rinsed with deonized water. All reagents were used as received. Deonized water was used to prepare all aqueous solutions. Tests of Al dissolution were performed in a Pyrex glass reactor heated in a water bath and 0010-938X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.corsci.2013.10.019 ⇑ Corresponding author. Tel.: +213 6 66 80 57 41; fax: +213 38 87 65 60. E-mail address: s_djerad@hotmail.com (S. Djerad). Corrosion Science 78 (2014) 343–352 Contents lists available at ScienceDirect Corrosion Science journal homepage: www.elsevier.com/locate/corsci