This paper describes the use of the Tafel polarization and electrochemical impedance spectroscopy technique (EIS) in order to study the corrosion inhibition process of aluminum in 0.5M H 2 SO 4 solution in presence of propargyl alcohol and zinc sulfate at the open circuit potential (OCP) in the room temperature. The Nyquist diagrams consisted of a capacitive semicircle at high frequencies followed by a well defined inductive loop at low frequency values. The impedance measurements were interpreted according to a suitable equivalent circuit. The results obtained showed that the addition of the propargyl alcohol inhibits the sulfuric acid corrosion of the aluminum. The inhibition efficiency increases with an increase in the propargyl alcohol concentration. The inhibition occurs through adsorption of the propargyl alcohol on the metal surface without modifying the mechanism of corrosion process. The inhibiting action propargyl alcohol is considerably enhanced by addition of zinc sulfate. Both the inhibitors obeyed the Langmuir isotherm and the thermodynamic calculations revealed that the adsorption of inhibitors was of physical nature.Keywords: Electrochemical Techniques; Corrosion; Aluminum; Zinc Sulfate; INTRODUCTIONAluminum and its alloys find a wide spread spectrum of technological applications because of their particular properties such as low density, good appearance and corrosion resistance. For these reasons, the corrosion behavior of these materials has attracted the attention of several investigators. Acid solutions are used for pickling, chemical and electrochemical etching of aluminum and its alloys. It is very important to add a corrosion inhibitor to decrease the corrosion rate of aluminum and its alloys in such solutions. Several authors [1][2][3][4] have studied the corrosion of aluminum and its alloys and their inhibition by organic inhibitors in acid solutions. The result of the investigations shows that acetylenic compounds are very effective in corrosion inhibition of metal in acid media [5]. Propargyl alcohol (PA) (2-propyn-1-ol) is one of the acetylenic alcohols and its inhibition effect has been discussed extensively [5][6][7][8][9][10] . The decisive role of the triple bonds of the PA molecule due to the π-electrons interacting with the metallic surfaces is generally accepted [11][12][13][14][15] . The adsorption of the inhibitor on the metal surface can markedly change the corrosion-resisting property of the metal 6,7 . The application of electrochemical impedance spectroscopy technique (EIS) as a new tool in corrosion research has resulted in a wealth of information concerning the methods of corrosion protection which were difficult to study with traditional dc techniques. This includes corrosion protection by conversion coatings 8 , polymer coating, and anodic films 9 . EIS has also provided information concerning corrosion protection by inhibitors 10 . In addition to specification of the physical properties of the system, the technique leads to important mechanistic and kinetic i...

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