---
title: "Painting work on metal surfaces"
subject: "Building Technology"
chapter: 9
key: "semester_6/building_technology:painting-metal"
source: https://www.bctengineer.com/q/semester_6/building_technology/painting-metal
site: BCT Engineering
---

# Painting work on metal surfaces

Building Technology · Chapter 9: Finishing works

- Asked in: 2077 Chaitra, 4 marks; 2065 Shrawan (old course), 4 marks (asked 2 times)
- Video: [Airless Spray Paint Metal Building? Step-by-Step how to Paint Metal Building like a Pro (SATISFYING)](https://www.youtube.com/watch?v=6FQlJr7T1Kw) — DIYTyler
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/painting-metal
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-9

## Question

Write down the steps for the painting work on metal surface (and masonry surface).

## Short answer

For metal, clean rust, apply primer (red oxide), stop dents, apply undercoat and finishing enamel. For masonry, dry plaster 3-4 weeks, apply alkali-resistant primer, putty, then two coats of emulsion or cement paint.

## Answer

#### Painting on metal surfaces (iron and steel)
1. **Cleaning:** remove rust, scale, oil and grease by scraping, wire brushing, sandpapering, or by a solvent wash or sand blasting.
2. **Priming coat:** soon after cleaning, apply a red oxide or zinc chromate primer by brush in one or two coats to prevent rusting. Allow 24 hours to dry.
3. **Stopping:** fill dents and holes with putty and sand it smooth.
4. **Second coat (undercoat):** apply an undercoat of enamel or oil paint. Let it dry and rub it down lightly.
5. **Finishing coat:** apply one or two coats of enamel or synthetic paint of the required colour, with 24 hours between coats.

Precautions: work in dry weather, do not paint a wet surface, and use primer and finish of the same make.

#### Painting on masonry (plastered) surfaces
1. **Surface preparation:** the plaster must be at least 3-4 weeks old and dry. Remove dust, grease and efflorescence with a wire brush, and fill cracks with putty.
2. **Priming:** apply an alkali-resistant primer or cement primer.
3. **Putty:** apply wall putty in 2 coats, rubbing with sandpaper after each.
4. **Painting:** apply two coats of emulsion, distemper or cement paint with a brush or roller, leaving 4-6 hours between coats.
5. **Cement paint:** the surface is wetted before application and cured afterwards.

## Check yourself

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

1. What is the first step in painting metal?
   A. Cleaning rust, scale, oil and grease
   B. Finishing coat
   C. Undercoat
   D. Applying putty
   Answer: A. Surface must be free of rust and grease before priming. (Key point: Cleaning)

2. Which primer is used on iron and steel?
   A. Whiting
   B. Red oxide or zinc chromate
   C. Alkali-resistant cement primer
   D. Shellac
   Answer: B. These primers prevent rust. (Key point: Primer)

3. How old should plaster be before painting?
   A. 1 hour
   B. Any age
   C. At least 3-4 weeks and dry
   D. 1 day
   Answer: C. Fresh plaster is alkaline and damp and would spoil paint. (Key point: Masonry age)

4. Which primer suits plastered masonry?
   A. Zinc chromate
   B. Red oxide
   C. Knotting
   D. Alkali-resistant or cement primer
   Answer: D. Alkali-resistant primer resists alkalinity of plaster. (Key point: Masonry primer)

## Related in Building Technology

- [Painting on masonry; causes and remedies of cracks](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Apainting-masonry-cracks) — Building Technology, chapter 9
- [Function of painting work](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Afunction-of-painting) — Building Technology, chapter 9
- [Specifications of brick masonry work](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Abrick-masonry-specs) — Building Technology, chapter 3, asked 2×
- [Masonry work, materials for 20 cum brickwork](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Abrickwork-20cum-1to6) — Building Technology, chapter 3
- [Paints, varnishes, painting procedures](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Apaints-varnish-064j) — Building Technology, chapter 9
- [Painting on new and old woodwork](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Apainting-new-old-wood) — Building Technology, chapter 9, asked 2×

## Related in other subjects

- [Preparing an older surface for painting](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Apaint-older-surface-preparation) — Civil Engineering Materials, chapter 9
- [Painting a new plastered surface](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Apaint-new-plastered-surface) — Civil Engineering Materials, chapter 9
- [Painting a new wood surface](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Apaint-new-wood-surface) — Civil Engineering Materials, chapter 9
- [Design steps of surface drainage](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Asurface-drainage-design-steps) — Transportation Engineering I, chapter 4, asked 3×