Corrosion-preventive petroleum, class 3, provides protection for which surfaces?

• A. Antifriction bearings, shock-strut pistons, and other bright metal surfaces
• B. Painted exterior surfaces
• C. Wood and composite surfaces
• D. Rubber seals

Answer: (A)

Class 3 corrosion-preventive petroleum is formulated to leave a thin, lubricating oil film on bright metal surfaces that are exposed to the atmosphere and may be in motion or under friction. This keeps corrosion at bay without creating a bulky coating that could impede moving parts. That’s why it’s specified for antifriction bearings, shock-strut pistons, and other bright metal surfaces that need continuous protection while still functioning properly.

Painted exterior surfaces are protected mainly by the paint coating itself, not by a light oil film, so this type of CPC isn’t intended to substitute for paint protection. Wood and composite surfaces aren’t metal, so a bright-metal film won’t be effective or appropriate there. Rubber seals can be adversely affected by petroleum products, so a light oil film used for bright metal components isn’t used on rubber seals.

In short, this class targets protecting bright metal surfaces, especially those involved in friction or movement, rather than nonmetallic surfaces or rubber components.