When an anodized surface coating is damaged in service, it can be partially restored by which method?

• A. Re-anodizing
• B. Polishing
• C. Painting
• D. Chemical surface treatment

Answer: (D)

Anodized aluminum relies on a porous oxide layer that protects the metal by sealing and forming a stable surface. When this coating is damaged in one area, the protective function can be restored locally by chemically treating that spot to seal the pores or convert the surface to a more resistant oxide. This re-passivation or sealing doesn’t remove material or require rebuilding the entire coating, so it’s suitable for partial repair. Re-anodizing would be more involved and usually applied to larger areas or whole surfaces, polishing removes or damages the coating further, and painting hides the issue without restoring the anodized protection. Chemical surface treatment directly restores the protective characteristics where needed.