Which of the following correctly lists the desired effects of using Alodine on aluminum alloy?

• A. A slightly rough surface
• B. Relieved surface stresses
• C. A smooth painting surface
• D. A slightly rough surface and Increased corrosion resistance

Answer: (D)

Alodine creates a chromate conversion coating on aluminum that serves two purposes: it increases corrosion resistance and leaves the surface slightly roughened. That roughness provides a good mechanical key for paint and sealants, while the protective chromate layer shields the metal from corrosion. It does not relieve surface stresses, and it does not produce a smooth painting surface. Because it combines both a mildly rough surface and enhanced corrosion resistance, the option describing those two effects is the best fit.