Electrochemical Corrosion Behavior of Bulk Nanocrystalline Aluminum in Formic Acid Solutions at Ambient Temperature

Background: The electrochemical corrosion properties of bulk nanocrystalline aluminum (BNC-Al) produced by severe rolling technique and its traditional polycrystalline aluminum (TPC-Al) counterpart in 0.022, 0.044, 0.066, 0.11, 0.22, 0.44 mol/L HCOOH solutions were studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) at ambient temperature. Method: The corrosion current densities and capacitances of double electrode layer of BNC-Al were less than those of TPC-Al respectively, and the polarization resistances of BNC-Al were larger than those of TPC-Al in 0.022, 0.044 mol/L HCOOH solutions. However, the corrosion current densities and capacitances of double electrode layer of BNC-Al were larger than those of TPC-Al respectively, and the polarization resistances of BNC-Al were less than those of TPC-Al in 0.066, 0.11, 0.22, 0.44 mol/L HCOOH solutions. The passivation of BNC-Al was enhanced in 0.066, 0.11, 0.22, 0.44 mol/L HCOOH solutions. Results and Conclusion: These results demonstrated that the corrosion resistances of BNC-Al were enhanced in 0.022 and 0.044 mol/L formic acid solutions at a low potential and in 0.066, 0.11, 0.22, 0.44 mol/L at a high potential, compared to those of TPC-Al. The possible reasons for these electrochemical results for BNC-Al and TPC-Al were proposed in this work.