In lubrication practice, what is the purpose of wetting?

• A. To form a continuous lubricant film over surfaces to reduce friction.
• B. To increase surface roughness.
• C. To evaporate lubricant quickly.
• D. To dry the surface.

Answer: (A)

Wetting is about how well a lubricant spreads across and adheres to the surfaces in contact. In lubrication practice, the aim is for the lubricant to spread and form a continuous film that covers the contact surfaces, so the surfaces are kept apart. This film reduces metal-to-metal contact, which lowers friction and helps carry away heat. When wetting is good, the liquid spreads to fill the microscopic valleys and asperities, creating a uniform lubricating layer. If wetting is poor, the lubricant stays in droplets and fails to form a complete film, leading to more direct surface contact and higher friction and wear. So the purpose of wetting is to form a continuous lubricant film that reduces friction, not to increase roughness, evaporate quickly, or dry the surface.