Electrodeposition of Al coating onto a 300M steel from AlCl3/acetamide deep eutectic solvents for corrosion protection

Aluminum coating was expected to be used for corrosion protection of 300M steel. Al coating was prepared using the galvanostatic electrodeposition from AlCl 3 /acetamide (1.3:1) system for the corrosion protection of 300M steel. This process was conducted at varying current density (2–8 mA·cm −2 ) and electrodeposition time (1 and 2 h). The chronopotentiometry revealed that the size of Al nucleus was proportional to the inverse of overpotential. Thus, the morphology of Al coating was characterized by scanning electron microscope and optical surface profiler. The results indicated a decrease in Al grain sizes and the roughness fluctuation with increasing current density. Moreover, the corrosion resistance of Al coatings was evaluated in a 3.5 wt% NaCl solution using the potentiodynamic polarization and electrochemical impedance spectroscopy test. It was illustrated that corrosion current density decreased by 57.8 % at 6 mA·cm −2 with the electrodeposition time increasing from 1 to 2 h, while the value decreased by 75.9 % with the current density raising from 5 to 6 mA·cm −2 for 2 h. Al coating electrodeposited at 6 mA cm −2 for 2 h represented the highest corrosion resistance with the charge transfer resistance of 5695 Ω·cm 2 , while the value of 300M steel was 914 Ω·cm 2 . Finally, X-ray diffraction pattern suggested that corroded coatings compositions included Al 2 O 3 , AlO(OH) and AlCl 3 ·6H 2 O. The study was considered to provide a promising method using AlCl 3 /acetamide to electrodeposit Al coatings for protecting 300M steel from corrosion.