Cleaning & Corrosion Control
What is the primary purpose of applying a water-displacing corrosion-preventive compound (CPC) to seams, hinges, and water-entrapment (bilge) areas of an airframe?
Answer
To penetrate crevices, displace trapped moisture, and leave a protective film that keeps the electrolyte away from the metal
Water-displacing CPCs are formulated to creep into seams and crevices, push out and displace water, and leave a thin protective film that excludes the electrolyte—ideal for water-entrapment areas. They are not conversion coatings (which build an oxide film by chemical reaction), not structural adhesives, and are not intended to improve electrical bonding.
Source: AC 43-4B ¶4.13.4, Preservation (corrosion preventive compounds "prevent corrosive materials from contacting and corroding bare metal surfaces … also displace water and other contaminants from the surfaces")
Not the answer
- To increase the electrical conductivity between adjacent panels for bonding
- To chemically convert the aluminum surface into a hard anodic oxide layer
- To serve as a structural adhesive that carries flight loads across the seam
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