In the context of CAT 4 maintenance, which action is taken to halt deterioration after approval has been obtained?

• A. Immediate paint removal
• B. No action necessary after approval
• C. Surface prep and touch up
• D. Replace entire assembly

Answer: (C)

Restoring the protective coating right at the damaged spot stops the deterioration by quickly reestablishing a barrier against moisture, oxygen, and chemicals. Surface prep and touch up involves cleaning the area, removing corrosion scales, feathering the edges, and applying primer and topcoat to seal the surface. This targeted action addresses the localized flaw and preserves the rest of the assembly without resorting to more drastic fixes.

Removing paint would remove protection and expose metal, making things worse. Doing nothing allows corrosion to continue unchecked. Replacing the entire assembly is unnecessary when the damage is limited to a small area and can be halted with a proper surface prep and touch up.