Paints & Coatings

Paints & Coatings

  • 1. Introduction
  • SpecX quick selector
  • 2. Main categories
  • 3. System comparison (quick reference)
  • 4. Selection matrix
  • 5. Performance parameters to specify
  • 6. Typical system build‑ups (examples)
  • 7. Common failures and remedies
  • 8. QA / QC checklist (site)
  • 9. Sample BOQ lines
  • 10. Test and reference standards

1. Introduction

Paint & coating systems protect, decorate and extend service life of substrates. The right selection depends on substrate (concrete, plaster, metal, wood), exposure (interior/exterior/wet/traffic), required service life, aesthetics and maintenance regime.

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SpecX quick selector

  • Interior wall: Acrylic primer + putty + 2 coats acrylic emulsion, DFT ≈ 100 µm
  • Exterior wall (high durability): Elastomeric acrylic system or polysiloxane topcoat over compatible primer
  • Metalwork: Sa2.5 blast + zinc-rich/epoxy primer + PU enamel topcoat
  • Medium-duty floor: Epoxy primer + SL epoxy 2–3 mm + aliphatic PU topcoat

Paint and coating systems protect, decorate, and extend service life of substrates. Selection depends on substrate, exposure, required service life, aesthetics, and maintenance.

2. Main categories

  • Interior emulsion / acrylics: Water-based decorative coatings for walls and ceilings; washable, low-VOC.
  • Distemper / lime-based paints: Traditional, breathable, low-cost; not washable.
  • Enamels (alkyd / PU): Solvent-based finishes for metal/wood; durable gloss or satin.
  • Epoxy coatings: Two-component, chemically resistant; floors, tanks, industrial (poor UV stability).
  • Polyurethane (PU) topcoats: Aliphatic PU for UV‑resistant exterior/trafficable finishes.
  • Polysiloxane / siliconized coatings: High-durability exteriors; excellent gloss retention and weathering.
  • Floor coatings: Epoxy/PU systems, polyaspartic, MMA, cementitious toppings.
  • Primers and sealers: Cement primer, epoxy primers for concrete, metal primers (zinc phosphate / epoxy zinc).
  • Specialty coatings: Anti‑carbonation, anti‑graffiti, intumescent, anti‑microbial.

3. System comparison (quick reference)

Property
Acrylic (Emulsion)
Enamel (Alkyd)
Epoxy
PU (Polyurethane)
Base
Water
Solvent
Solvent / Solvent‑free
Solvent / Solvent‑free
Film type
Flexible
Hard
Rigid
Flexible
UV resistance
Excellent
Poor
Poor
Excellent
Chemical resistance
Low
Moderate
High
High
Typical use
Walls
Metal / wood
Floors, tanks
Exterior/high‑performance topcoat

4. Selection matrix

Substrate
Interior
Exterior
High traffic / industrial
Plaster / putty
Acrylic emulsion
Acrylic elastomeric / polysiloxane
Epoxy flooring under screed
Concrete (slab)
Acrylic / PU
Silicone / polysiloxane
Epoxy or PU screed
Mild steel
Alkyd / PU
PU or polysiloxane over primer
Epoxy / PU systems
Wood / joinery
Alkyd enamel / PU
Exterior PU / marine varnish
PU / alkyd

5. Performance parameters to specify

Parameter
Typical requirement
Reference
DFT (dry film thickness)
80–150 µm
IS 101
Adhesion
> 1 MPa
ASTM D4541
Flexibility
No cracking (5 mm mandrel)
IS 101
UV resistance
1000 hrs (no chalking)
ASTM G154
WVTR
> 100 g/m²/day
ASTM E96

6. Typical system build‑ups (examples)

  • Interior wall: Primer (acrylic) → Putty → 2 coats acrylic emulsion.
  • Exterior high‑performance wall: Primer/bonding → Elastomeric acrylic base → Elastomeric acrylic or polysiloxane topcoat.
  • Industrial floor (medium duty): Surface prep → Epoxy primer → Epoxy screed/self‑leveling → PU topcoat.
  • Metalwork: Blast clean to Sa2.5 → Zinc‑rich/epoxy primer → PU enamel topcoat.

7. Common failures and remedies

⚠️
  • Peeling/blistering → high substrate moisture or inadequate priming; verify moisture, reprime, and recoat
  • Chalking → UV/binder degradation; switch to acrylic/polysiloxane, surface prep, recoat
  • Efflorescence → salts and rising damp; desalinate, use breathable/salt‑tolerant primer, address source
  • Yellowing (enamels) → sunlight on alkyd/aromatic PU; use aliphatic PU for exteriors

8. QA / QC checklist (site)

  • Substrate dryness < 12–15% (system‑dependent).
  • Pull‑off adhesion tests (samples) per spec.
  • DFT gauge checks at random locations.
  • Visual acceptance: uniform sheen, no runs, sags, orange peel.
  • Respect curing and re‑coat windows.

9. Sample BOQ lines

  • “Providing and applying two coats of acrylic emulsion paint over one coat of acrylic primer on prepared plaster surface. DFT: nom. 100 µm. Unit: m².”
  • “Providing and applying epoxy floor coating, 3 mm total DFT, including surface prep, primer, and testing: m².”

10. Test and reference standards

  • IS 15489 — Interior emulsion paints
  • IS 2932 — Exterior emulsion paints
  • ASTM D4541 — Pull‑off adhesion
  • ASTM D4060 — Abrasion (Taber)
  • ISO 4628 — Degradation (chalking/peeling)