알루미늄 5052 합금의 산화피막 성장 및 내식성 연구

Study on Corrosion and Oxide Growth Behavior of Anodized Aluminum 5052 Alloy

Abstract

Anodization techniques are widely used in the area of surface treatment of aluminum alloys because of its simplicity, low-cost and good corrosion resistance. In this study, we investigated the relationship between the properties (porosity and thickness) of anodic aluminum oxide (AAO) and its corrosion behavior. Aluminum 5052 alloy was anodized in 0.3 M oxalic acid at $0^{\circ}C$. The anodizing of aluminum 5052 was performed at 20 V, 40 V and 60 V for various durations. The corrosion behavior was studied in 3.5 wt % NaCl using potentiodynamic polarization method. Results showed that the pore diameter and thickness increased as voltage and anodization time increased. The relatively thick oxide film revealed a lower corrosion current density and a higher corrosion potential value.

Fig. 1. FE-SEM of surface morphology and thickness of the aluminum oxide prepared by modulating anodization time under applied voltage at 20 V.

Fig. 2. Variation of pore diameter and thickness according to anodization time at 20 V; (a) pore diameter and interpore distance (b) thickness.

Fig. 3. FE-SEM of surface morphology and thickness of the aluminum oxide prepared by modulating anodization time under applied voltage at 40 V.

Fig. 4. Variation of pore diameter and thickness according to anodization time at 40 V; (a) pore diameter and interpore distance (b) thickness.

Fig. 5. FE-SEM of surface morphology and thickness of the aluminum oxide prepared by modulating anodization time under applied voltage at 60 V.

Fig. 6. Variation of pore diameter and thickness according to anodization time at 60 V; (a) pore diameter and interpore distance (b) thickness.

Fig. 7. EDS analysis after anodization with anodization time and voltage; (a) 20 V, (b) 40 V, (C) 60 V.

Fig. 8. Potentiodynamic polarization curves for aluminum oxide formed at 20 V by controlling anodization time.

Fig. 9. Potentiodynamic polarization curves for aluminum oxide formed at 40 V by controlling anodization time.

Fig. 10. Potentiodynamic polarization curves for aluminum oxide formed at 60 V by controlling anodization time.

Fig. 11. Protective efficiency for the anodic aluminum oxides forms at 20 V, 40 V and 60 V.

Table 1. Chemical compositions of Al 5052 alloy

Table 2. Porosity of specimens according to anodization time and voltage

Table 3. Result of potentiodynamic polarization tests for aluminum formed at 20 V.

Table 4. Result of potentiodynamic polarization tests for aluminum formed at 40 V.

Table 5. Result of potentiodynamic polarization tests for aluminum formed at 60 V.