---
title: "Lubricant functions and paint [partly illegible]"
subject: "Engineering Chemistry"
chapter: 8
key: "semester_2/engineering_chemistry:lubricant-paint-partial"
source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/lubricant-paint-partial
site: BCT Engineering
---

# Lubricant functions and paint [partly illegible]

Engineering Chemistry · Chapter 8: Lubricants and Paints

- Asked in: 2071 Magh
- Video: [Lubricants || Lubricant Important Functions And Classification ||Lubrication ||Engineering Chemistry](https://www.youtube.com/watch?v=Kuj2X6ncPBc) — Chemistry by Dr. Anjali Ssaxena
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/lubricant-paint-partial
- Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-8

## Question

What are the functions of lubricants? What is paint? Descr[ibe ?]

## Short answer

Lubricants reduce friction, wear, heat, seal, prevent corrosion, clean, and save energy. Paint is a mechanical dispersion of pigment in a drying oil. Its constituents are pigment, vehicle (linseed oil), thinner, drier, extender, and plasticiser.

## Answer

**Reading:** the question is cut off after "Describe"; I read it as "What are the functions of lubricants? What is paint? Describe its constituents."

#### Functions of lubricants
1. **Reduces friction** between moving surfaces by forming a thin film that separates them.
2. **Reduces wear and tear**, which increases the life of machine parts.
3. **Acts as a coolant:** carries away heat produced by friction.
4. **Acts as a seal:** prevents leakage of gases, e.g. between piston rings and cylinder.
5. **Prevents corrosion** by coating metal surfaces from air and moisture.
6. **Cleans** by washing away dirt, metal particles and carbon deposits.
7. **Saves energy:** smoother motion means less power loss and higher efficiency; also reduces noise and vibration.

#### Paint
Paint is a mechanical dispersion of pigment in a drying oil (vehicle) with thinner, drier and other additives, which dries to a thin protective and decorative film.

#### Constituents of paint
- **Pigment:** gives colour, opacity and strength (TiO₂, ZnO, iron oxide, white lead).
- **Vehicle (drying oil):** carrier that forms the film on oxidation (linseed oil).
- **Thinner:** reduces viscosity and evaporates after application (turpentine, mineral spirit).
- **Drier:** speeds up drying of the oil (Pb, Mn or Co linoleates).
- **Extender (filler):** barytes, gypsum, china clay; reduces cost and adds body.
- **Plasticiser:** prevents cracking of the film.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which pair of functions are lubricant functions?
   A. Increasing friction and acting as a dye
   B. Acting as coolant and as seal
   C. Producing heat and promoting rust
   D. Thickening cement and cooling pigments
   Answer: B. Lubricants carry away heat and seal gases, e.g. between piston rings and cylinder. (Key point: Cooling and sealing)

2. How does a lubricant prevent corrosion?
   A. By dissolving rust
   B. By heating the metal
   C. By absorbing oxygen chemically
   D. By coating metal surfaces from air and moisture
   Answer: D. The oil film shields metal from air and moisture. (Key point: Corrosion)

3. What is the role of pigment in paint?
   A. To thin the paint
   B. To give colour, opacity and strength
   C. To speed up drying
   D. To prevent cracking
   Answer: B. Pigments such as TiO2 and ZnO provide colour and opacity. (Key point: Pigment)

4. What is the function of a drier in paint?
   A. To reduce viscosity
   B. To reduce cost
   C. To prevent film cracking
   D. To speed up the drying of the oil
   Answer: D. Driers (Pb, Mn, Co linoleates) speed up drying of the oil. (Key point: Drier)

## Related in Engineering Chemistry

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- [Lubricants and their functions](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Alubricants-functions) — Engineering Chemistry, chapter 8, asked 4×
- [Dehydrohalogenation; mechanism and kinetics of E1 [partly illegible]](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Ae1-kinetics) — Engineering Chemistry, chapter 10, asked 2×
- [Werner's postulates; IUPAC names [partly illegible]](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Awerner-postulates-iupac) — Engineering Chemistry, chapter 6
- [High and plastic explosives; nitrocellulose, TNT [partly illegible]](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Anitrocellulose-tnt) — Engineering Chemistry, chapter 7

## Related in other subjects

- [Functions of paint](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Afunctions-of-paint) — Civil Engineering Materials, chapter 9, asked 3×
- [Lubricant properties, additives and SAE grading](https://www.bctengineer.com/question.md?key=semester_6%2Finternal_combustion_engines%3Alubricant-properties-additives-sae-grading) — Internal Combustion Engines, chapter 6