Available online at www.sciencedirect.com Materials Chemistry and Physics 107 (2008) 281–288 The effect of inhibitor on the corrosion of aluminum alloys in acidic solutions R. Rosliza a,∗ , W.B. Wan Nik b , H.B. Senin b a TATI University College, Teluk Kalong, 24000 Kemaman, Terengganu, Malaysia b Faculty of Science and Technology, University Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu, Malaysia Received 5 March 2007; received in revised form 18 July 2007; accepted 18 July 2007 Abstract The corrosion inhibition of Al and its alloys is the subject of tremendous technological importance due to the increased industrial applications of these materials. This study reports the results of weight loss, polarization and electrochemical impedance spectroscopic (EIS) measurements on the corrosion inhibition of AA6061 and AA6063 aluminum alloys in acidic solutions using sodium benzoate as an inhibitor. The results showed that addition of sodium benzoate retards the rate of dissolution and hence inhibits the corrosion of the aluminum alloy in acidic solutions. The inhibition efficiency increases with the increase of immersion time in acetic acid however it displays a different behavior in sulfuric acid. Electrochemical studies showed that there was a significant increase in overall resistance after addition of sodium benzoate, when compared to the case without inhibitor. Langmuir adsorption isotherm fits well with the experimental data. © 2007 Elsevier B.V. All rights reserved. Keywords: Alloys; Heat treatment; Electrochemical technique; Adsorption 1. Introduction Aluminum and its alloys represent an important category of materials due to their high technological value and wide range of industrial applications, especially in aerospace and household industries. The use of these materials in light weight instal- lations is widespread. Aluminum and its alloy, however, are reactive materials and are prone to corrosion [1]. As such, cor- rosion of aluminum and its alloy has been a subject of numerous studies due to their importance in the recent civilization. Many researchers have devoted their work to study the corrosion of alu- minum in different aqueous solutions [1,2], and also the research into their electrochemical behavior and corrosion inhibition in wide variety of conducting solutions [3]. The use of inhibitors is one of the most practical methods for protection against corrosion, especially in acidic solutions. Benzoate compounds offer interesting possibilities for corro- sion inhibition and are of particular interest because of their safe use and high solubility in water [4]. The adsorption of ∗ Corresponding author. Tel.: +60 96683301; fax: +60 96694660. E-mail addresses: rosliza@tati.edu.my (R. Rosliza), senin@kustem.edu.my (H.B. Senin). the absorbate on the metal surface can markedly change the corrosion-resisting property of the metal [5], and so the study of the relations between the adsorption and corrosion inhibition is a great importance. In the present work, weight loss, potentiody- namic polarization and impedance measurements are applied to investigate the corrosion behavior of aluminum alloys in acidic solutions. 2. Materials and methods 2.1. Material The aluminum alloys employed for this study were AA6061 and AA6063. The chemical composition of these alloys, in weight percent, is shown in Table 1. The test solutions used for the investigation were diluted sulfuric acid 0.1 M and acetic acid 0.5 M and the inhibitor used was sodium benzoate (NaBz). The inhibitor was separately added in turn to each of the above test solutions in a ratio one part inhibitor to 10 part test solutions. 2.2. Weight loss experiment Specimens were cut into 25 mm × 25 mm × 3 mm and 25 mm × 25 mm × 1.5 mm coupons for immersion tests. Before exposure, the samples were mechanically polished using 400, 500 and 600 emery papers and lubricated using distilled water. The polished samples were cleaned with acetone, washed 0254-0584/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2007.07.013