Question 1
(a) Question 1: (a) List any six primers used in decorative painting.
(b) Explain any three of the following terms:
(i) pretreatment;
(ii) galvanizing;
(iii) mill scale;
(iv) acid pickling.
Observation
(a) - Red lead primer;
- Calcium plumbate primer;
- Zinc chromate primer
- Metallic lead primer;
- Red oxide primer;
- Zinc rich primer
- Alkyd-based aluminium primer;
- Acrylic primer;
- Pink wood primer
- Aluminium wood primer;
- Lead free or leadless primer;
- Etch primer;
- Lead based primer;
- Alkaline resisting primer;
- All purpose, universal/multi-surface primer;
- Quick-drying acrylic metal primer;
- Preservative primer;
- Stabilising/solution primer.
(b) (i) Pre-treatment
It is a method of coating metal before painting to improve the durability of paint by ensuring better adhesion and resisting corrosion.
(ii) Galvanizing
A zinc coating applied on iron or steel to protect it from corrosion.
(iii) Mill scale
- A thin skin layer of iron oxide which covers the surface of steel when it leaves the rolling mill.
- A form of iron oxide which adheres tightly to the new metal in a laminated structure in course of time it gets loose and flakes providing an unstable basis for a paint system.
(iv) Acid pickling
- A method of treating iron or steel by immersion in diluted acids thus protecting it from corrosion.
- A process of removing rust from steel by immersing it in a bath containing acid solution.