Code of practice for the painting of nonferrous metals in buildings, Part 1: Pretreatment

Scope of IS 2524 Part 1 (1968) – Painting of Non-Ferrous Metals

This part of IS 2524 covers guidelines for efficient planning and execution of painting on non-ferrous metals, focusing on:

• Nature of metal/alloy: Identify the specific metal or alloy.
• Surface condition: Check for scale, rust, moisture, grease, salts, etc.
• Service environment: Consider atmospheric or operational conditions affecting paint performance.
• Previous finish: Essential for maintenance repainting.

Key Specifications & Considerations

Factory Pretreatment Methods (Clause 6.2.1)

• Mechanical treatment (abrasion, blasting)
• Solvent cleaning (removal of grease/oils)
• Chemical treatment (acid/alkaline cleaning)
• Anodic treatment (electrochemical surface modification)

flowchart TD
    A[Identify Metal/Alloy] --> B[Check Surface Condition]
    B --> C[Evaluate Environment]
    C --> D[Determine Previous Finish]
    D --> E[Select Pretreatment Method]
    E --> F[Mechanical | Solvent | Chemical | Anodic]
    F --> G[Apply Paint Coating]

This structured approach ensures durable paint performance on non-ferrous metals per IS 2524 Part 1.

IS 2524 Part 1 (1968) - Key Definitions & Specifications

• Definitions: Painting terms follow IS 1303:1963 (Glossary of terms related to painting). Refer to IS 1303 for standard definitions like primer, enamel, undercoat, etc.

• Necessary Information for Painting Non-Ferrous Metals (Clause 3.1):

  • Metal type/alloy to be painted.
  • Surface condition: presence of scale, rust, moisture, grease, salts.
  • Service environment of the paint coating.
  • Previous finish details (for maintenance repainting).

• Design Considerations for Factory Pretreatment (Clause 6.2.1):

  • Mechanical treatment (abrasion, blasting)
  • Solvent cleaning (removal of grease/oil)
  • Chemical treatment (acid/alkaline cleaning)
  • Anodic treatments (electrochemical surface modification)

Summary Table: Factory Pretreatment Methods

flowchart LR
    A[Metal Surface] --> B[Mechanical Treatment]
    B --> C[Solvent Cleaning]
    C --> D[Chemical Treatment]
    D --> E[Anodic Treatment]
    E --> F[Ready for Painting]

Note: For detailed painting terms, always consult IS 1303:1963 alongside IS 2524 Part 1.

IS 2524 Part 1: Necessary Information for Painting Non-Ferrous Metals

Key Points from Clause 3.1 (Necessary Information):

For effective painting, gather detailed data on:

• Metal/Alloy Type: Identify the exact nature of the non-ferrous metal.
• Surface Condition: Check for scale, rust, moisture, grease, salts, or other contaminants.
• Service Environment: Understand environmental exposure (humidity, chemicals, temperature).
• Previous Finish: For repainting, know the existing coating type and condition.

Surface Preparation (Clause 3.3):

• Galvanized Steel/Zinc Sheets: Must be degreased.
• Surface should be pretreated or weathered (~3 months in clean air) for adhesion.
• Alternatively, use a special primer designed for galvanized surfaces.

Rounding Off Values (Clause 0.6):

• Follow IS 2-1960 for rounding test/analysis results.
• Retain the same number of significant digits as specified.

Summary Table: Surface Prep & Painting Info

Reference:

• IS 1303-1963 for painting definitions
• IS 2-1960 for rounding rules
• BS CP 231:1966 for international coordination

flowchart TD
    A[Start: Painting Non-Ferrous Metal] --> B{Identify Metal Type}
    B --> C[Check Surface Condition]
    C --> D{Contaminants Present?}
    D -- Yes --> E[Clean Surface: Remove rust, grease, salts]
    D -- No --> F[Proceed]
    E --> F
    F --> G{Is Metal Galvanized Steel/Zinc?}
    G -- Yes --> H[Degrease + Pretreat or Weather 3 months or Use Primer]
    G -- No --> I[Standard Painting Procedure]
    H --> J[Apply Paint]
    I --> J
    J --> K[Finish]

This ensures

IS 2524 Part 1 - Design Considerations for Painting Non-Ferrous Metals

Key Points from Clause 4.1:

• Design for Accessibility: Surfaces must be accessible for painting and priming.
• Surface Suitability: Ensure surfaces allow good adhesion and maximum paint protection.
• Longevity: Design to maximize paint life and protection against environment.

Important Factors Affecting Design (Clause 3.1):

• Metal Type: Nature of metal/alloy influences paint choice.
• Surface Condition: Remove scale, rust, moisture, grease, salts before painting.
• Environment: Consider exposure conditions (humidity, chemicals, temperature).
• Previous Finish: Knowledge of old coatings helps in maintenance painting.

Pretreatment Methods (Clause 6.2.1):

Practical Design Tips:

• Avoid crevices/traps where moisture accumulates.
• Provide smooth, cleanable surfaces.
• Use compatible primers for the specific metal.
• Plan for repainting and maintenance access.

Glossary & Standards:

• Refer IS 1303-1963 for painting terminology.
• Follow rounding rules for numerical values as per IS 2524.

flowchart LR
    A[Design Surface] --> B[Ensure Accessibility]
    B --> C[Surface Preparation]
    C --> D{Pretreatment Method}
    D --> |Mechanical| E[Blasting/Grinding]
    D --> |Solvent| F[Degreasing]
    D --> |Chemical| G[Acid/Alkali Cleaning]
    D --> |Anodic| H[Electrochemical Treatment]
    E & F & G & H --> I[Priming]
    I --> J[Painting]
    J --> K[Maintenance/Repainting]

This ensures durable paint performance on non-ferrous metals per IS 2524 Part 1.

IS 2524 Part 1 (1968) – Key Points on Characteristics & Painting of Non-Ferrous Metals

1. Characteristics to Consider (Clause 3.1)

• Nature of metal/alloy: Zinc, copper, lead, pure aluminium, and aluminium alloys have different corrosion and painting needs.
• Surface condition: Remove scale, rust, moisture, grease, salts before painting.
• Environment: Consider atmospheric corrosiveness and exposure.
• Previous finish: Important for maintenance repainting.

2. Painting Requirements (Clause 5.2.6)

• Non-ferrous metals as protective coatings (e.g., sprayed zinc) are porous/rough → different pretreatment than solid sheets.
• Unpainted use is more restricted when metals protect steel/iron.

3. General Painting Guidelines

4. Pretreatment Summary (from Part 1)

• Clean surface thoroughly.
• Remove contaminants (scale, rust, grease).
• Use suitable primers based on metal type.
• Ensure dry surface before painting.

Example: Pretreatment Steps for Aluminium

1. Degrease surface.
2. Remove oxides by chemical etching or mechanical abrasion.
3. Apply compatible primer (e.g., chromate-based).
4. Paint with recommended system.

flowchart TD
    A[Non-Ferrous Metal Surface] --> B{Surface Condition}
    B -->|Clean| C[Apply Primer]
    B -->|Contaminated| D[Surface Cleaning]
    D --> C
    C --> E[Apply Paint System]
    E --> F[Finished Coating]

References: IS 2524 Part 1 (1968) covers pretreatment; Part 2 covers painting schedules. Use both for complete guidance.

IS 2524 Part 1 - Surface Preparation & Pretreatment Summary

Key Pretreatment Methods (Clause 6.2.1)

• Mechanical treatment: Abrasion or cleaning to remove rust, scale.
• Solvent cleaning: Remove oil, grease, contaminants.
• Chemical treatment: Chromate or etching solutions.
• Anodic treatments: Electrochemical surface modification.

Factory Pretreatment (Clause 6.3.2)

• Solvent cleaning mandatory before any treatment.
• Chromate treatment: Dip/spray with dilute chromic acid mix → thin amorphous chromate coating for corrosion resistance & paint adhesion.
• Aqueous chromic organic treatment: Roller/dip with chromium resin → corrosion-resistant film.
• Etching or wash primers: As per 6.2.1.3(j), acid or mordant based; rinse thoroughly to remove residues.

Surface Repair (Clause 6.2.2.2)

• Inspect pretreated surfaces.
• Degrease damaged areas with solvent.
• Remove corrosion products.
• Touch up with wash/etching primer.
• Apply primer, putty, finish coats.

Untreated Surfaces (Clause 6.3.3.1)

• Degrease thoroughly.
• Apply wash/etch primers or etching solutions.
• Avoid copper-containing mordants.
• Rinse thoroughly after etching.
• Weathered galvanized surfaces can be painted after cleaning.
• Abrasion with emery cloth + solvent wash for small areas.

Important Notes:

flowchart TD
    A[Surface Preparation] --> B[Solvent Cleaning]
    B --> C{Surface Type}
    C -->|Factory Pretreated| D[Inspect & Repair]
    C -->|Untreated| E[Degrease & Etch]
    D --> F[Touch up with Primer

IS 2524 Part 1: General Pretreatment Principles

Key Points from Clauses:

• 6.1.2: Pretreatment is classified into:

  • Factory Pretreatment: Controlled environment processes.
  • On-site Pretreatment: Field application methods.

• 6.2.2 & 6.3.3: Focus on On-site Pretreatment, emphasizing surface preparation before protective coatings.

General Pretreatment Guidelines:

• Surface Cleaning: Remove dirt, oil, grease, rust, and mill scale.
• Methods Include:
  • Solvent cleaning
  • Abrasive blasting (e.g., sand, grit)
  • Chemical cleaning (acid pickling)
• Surface Profile: Achieve a roughness suitable for coating adhesion, typically 50-75 microns.

Typical Pretreatment Process Flow:

flowchart LR
    A[Surface Inspection] --> B[Cleaning Method Selection]
    B --> C[Cleaning Execution]
    C --> D[Surface Profile Check]
    D --> E[Apply Primer/Coating]

Important Specifications:

Note: Always refer to IS 2524 Part 1 for substrate-specific pretreatment details and ensure compliance with coating manufacturer's instructions.

Pretreatment of Aluminium and Alloys (IS 2524 Part 1 - Clause 6.2.1.3 & 6.2.2.1)

Key Chemical Treatments (Clause 6.2.1.3)

• Alkaline Etch: Caustic soda solution etches metal, removes oxide film; followed by nitric/phosphoric acid; requires conversion coating.
• Sulphuric-Chromic Acid Etch: Passive surface for mild exposure; suitable for clear finishes.
• Phosphoric Acid Cleaners: Thin phosphate film promotes paint adhesion; applied by swabbing/dipping.
• Acid Fluoride Deoxidizer: Nitric/sulphuric acid + chromic acid + fluoride at 35–55°C; clean uniform surface.
• Amorphous Phosphate Treatment: Immersion/spray with phosphoric, chromic, hydrofluoric acids; corrosion inhibition + paint durability.
• Carbonate Chromate Treatment: Hot dilute sodium carbonate + potassium chromate; thin conversion coating.
• Amorphous Chromate Treatment: Chromic acid + fluoride accelerators; golden to brown oxide coating; may require prior deoxidizing.
• Etching/Wash Primers: Acid-bound resinous film to enhance paint adhesion.

Surface Preparation for Untreated/Temporary Protected Surfaces (Clause 6.2.2.1)

• Remove temporary protective films with solvents before further treatment.
• Remove rolling lubricants with solvent + abrasive paper.
• Remove flux residues (welding/soldering) with 10% formic acid solution.
• Heat-hardened alloys: mechanical roughening + degreasing.
• Avoid steel wire brushes; use stainless steel brushes for corrosion removal.
• Chemical corrosion removal requires inhibited acids + thorough rinsing.
• Cast alloys often require only degreasing before painting.

Summary Table of Chemical Treatments

Pretreatment of Zinc and Galvanized Steel (IS 2524 Part 1, 1968)

Key Points from Clauses 6.3.1 to 6.3.3.1 & 5.4:

• Degreasing: Essential before painting to remove oil, grease, and contaminants (solvent cleaning per 6.2.1.2).
• Chromate Treatment (6.3.2b):
  • Dip/spray with dilute chromic acid mixture.
  • Forms a thin amorphous chromate coating.
  • Enhances corrosion resistance & paint adhesion.
• Aqueous Chromic Organic Treatment (6.3.2c):
  • Application by roller, dip, or squeeze rolls.
  • Produces corrosion-resistant film improving paint adhesion.
• Etching or Wash Primers (6.3.2d & 6.3.3.1b):
  • Use acid or mordant solutions (avoid copper-based mordants).
  • Rinse thoroughly after etching to remove residues.
• Surface Weathering (6.3.3.1c):
  • Allow zinc to weather until bright spangles disappear.
  • Surface then suitable for painting without degreasing.
• Mechanical Abrasion (6.3.3.1d):
  • Emery cloth with solvent for small areas.
  • Produces fine matt surface for painting.
• Corrosion Considerations (5.4):
  • Paint zinc/galvanized steel in damp, polluted, or industrial atmospheres.
  • Life of coating ∝ zinc weight.
  • Remove rust to bright metal & apply corrosion-inhibiting primer if rusted.

Summary Table of Pretreatment Methods

Pretreatment of Copper and Copper Alloys
(IS 2524 Part 1 - Clauses 5.6, 6.2.1, 6.4.2, 6.6)

Key Specifications:

• Cleaning:

  • Use organic solvents to thoroughly clean the surface.
  • Remove all copper dust after abrasive treatment to prevent verdigris stains.

• Surface Roughening:

  • Lightly roughen with fine abrasive paper to improve paint adhesion.

• Priming:

  • Apply one coat of etching primer to seal the metal and improve paint adhesion.
  • Factory electro-deposited tin coating is recommended for enhanced preparation.

• Factory Pretreatment Methods (Clause 6.2.1):

  • Mechanical (abrasive) treatment
  • Solvent cleaning
  • Chemical treatment
  • Anodic treatments (can also create conversion coatings)

• Conversion Coatings (Clause 6.4.2):

  • For outdoor/high corrosion environments, use conversion coatings (e.g., dichromate method) for superior protection and paint adhesion.

Summary Table of Pretreatment Steps

flowchart LR
    A[Start: Copper Surface] --> B[Clean with Organic Solvent]
    B --> C[Light Abrasive Roughening]
    C --> D[Remove Copper Dust]
    D --> E[Apply Etching Primer (1 Coat)]
    E --> F{Factory Preparation?}
    F -- Yes --> G[Electro-deposited Tin Coating]
    F -- No --> H[Proceed to Painting]
    G --> H

Pretreatment of Cadmium Coated Steel (IS 2524 Part 1 - 1968)

Key Points from Clauses:

• Clause 5.5: Cadmium is reactive; pretreatment before painting is recommended.
• Clause 6.5: Cadmium behaves like zinc in pretreatment, but weathering is not required.
• Clause 6.2.1: Factory pretreatment includes:
  • Mechanical treatment
  • Solvent cleaning
  • Chemical treatment
  • Anodic treatments
• Clause 6.3.2: Surface cleaning must remove oil/grease by solvent cleaning before further treatments.

Recommended Pretreatment Methods:

Summary Flowchart of Pretreatment Process:

flowchart TD
    A[Start: Cadmium Coated Steel] --> B[Mechanical Treatment]
    B --> C[Solvent Cleaning (Remove oil/grease)]
    C --> D{Choose Chemical Treatment}
    D --> E[Chromate Treatment]
    D --> F[Aqueous Chromic Organic Treatment]
    D --> G[Etching / Wash Primer]
    E --> H[Painting]
    F --> H
    G --> H

Note:

• Weathering step is not required for cadmium (unlike zinc).
• Ensure all surfaces are thoroughly cleaned before chemical treatments to maximize adhesion and corrosion protection.

Pretreatment of Lead and Terne Plate (IS 2524 Part 1 - 1968)

Key Points & Specifications:

• Terne Plate (Lead-Tin Alloy) - Clause 5.8:

  • No special restrictions except avoid graphite in primer.
  • If painting issues arise, use an etching treatment to improve adhesion.

• Lead - Clause 6.7:

  • New lead surfaces should be pretreated before painting.
  • Preferred method: apply an etching primer.
  • Alternative: treat with ~20% ortho-phosphoric acid solution, then wash and dry thoroughly.

• Protection from Acidic Hardwoods - Clause 5.2.2:

  • Metals like lead and terne plate are vulnerable to acidic hardwoods (oak, chestnut).
  • Take adequate precautions to prevent rainwater runoff from wood onto metals.

• Factory Pretreatment - Clause 6.3.2:

  • Clean surface of oil/grease via solvent cleaning.
  • Recommended treatments:
    • Chromate treatment: Dip/spray with dilute chromic acid solution for corrosion resistance.
    • Aqueous chromic organic treatment: Roller or dip application of chromium resin for corrosion resistance.
    • Etching or wash primers: Follow guidelines in Clause 6.2.1.3(j).

Summary Table:

flowchart TD
    A[New Lead/Terne Surface] --> B{Clean Surface}
    B -->|Oil/Grease present| C[Solvent Cleaning]
    B -->|Clean| D{Select Pretreatment}
    D --> E[Etching Primer]
    D -->

Pretreatment of Magnesium and Its Alloys (IS 2524 Part 1 - 1968)

Key Specifications & Treatments

• Mechanical (Abrasive) Treatments: Suitable for mildly corrosive indoor conditions; includes sanding, blasting.
• Solvent Cleaning: Removes oils and contaminants before further treatment.
• Alkaline Solution Treatments & Acid Pickling: Preliminary cleaning steps that do not produce protective conversion coatings.
• Conversion Coating (Dichromate Method): Essential for outdoor/high-corrosion environments to enhance corrosion resistance and paint adhesion.
• Anodic Treatments: Simultaneously clean and form conversion coatings on magnesium alloys.

Important Notes

• Magnesium forms an alkaline oxidation film; painting requires careful surface prep.
• In clean indoor atmospheres, Mg corrodes slower than steel; outdoors, corrosion accelerates especially with chlorides (sea water).
• Protection by painting + chemical pretreatment is recommended, especially in aggressive environments.

Summary Table of Pretreatment Methods

Conversion Coating (Dichromate) - General Steps

1. Clean surface (mechanical + solvent)
2. Apply alkaline or acid cleaning
3. Dip in dichromate solution (conversion coating)
4. Rinse and dry
5. Paint application

flowchart LR
    A[Mechanical Abrasion] --> B[Solvent Cleaning]
    B --> C[Chemical Treatment (Alkaline/Acid)]
    C --> D{Environment?}
    D -->|Mild Indoor| E[Paint Directly]
    D -->|Outdoor/Severe| F[Conversion Coating (Dichromate)]
    F --> G[Paint Application]

For best corrosion resistance and paint adhesion on magnesium alloys, use conversion coating or anodic treatments before painting, especially outdoors.

Pretreatment of Tin (IS 2524 Part 1 - 1968)

• Key Objective: Ensure good paint adhesion by thorough degreasing and surface roughening (Clause 5.9).

Factory Pretreatment Methods (Clause 6.2.1)

1. Mechanical Treatment: Surface roughening by abrasion.
2. Solvent Cleaning: Removal of oil, grease, and contaminants.
3. Chemical Treatment: Includes chromate and etching treatments.
4. Anodic Treatment: Electrochemical surface modification.

Specific Treatments (Clause 6.3.2)

• Solvent Cleaning: Essential before any further treatment.
• Chromate Treatment: Dip/spray in dilute chromic acid mixture for corrosion resistance and paint adhesion.
• Aqueous Chromic Organic Treatment: Application of chromium-containing resins by dip or roller for corrosion protection.
• Etching or Wash Primers: Surface etching to improve paint bonding (refer to 6.2.1.3(j)).

Summary Table of Pretreatment Steps for Tin

flowchart TD
    A[Start: Tin Surface] --> B[Degreasing (Solvent Cleaning)]
    B --> C[Surface Roughening (Mechanical)]
    C --> D{Choose Treatment}
    D -->|Chromate| E[Chromate Dip/Spray]
    D -->|Chromic Organic| F[Aqueous Chromic Resin Application]
    D -->|Etching| G[Etching or Wash Primer]
    E --> H[Paint Application]
    F --> H
    G --> H

Note: Always avoid graphite in primers for terne plates (Lead-Tin) as per Clause 5.8.

Inspection and Maintenance of Pretreated Surfaces (IS 2524 Part 1)

Key Steps (Clause 6.2.2.2)

• Inspect pretreated/primed surfaces carefully.
• Degrease damaged areas thoroughly by solvent swabbing.
• Remove corrosion products completely.
• Touch up damaged areas with:
  • Wash or etching primer, or
  • Suitable chemical pretreatment solutions.
• Apply appropriate primer, putty, and finish coats on repaired areas.

Factory Pretreatment Methods (Clause 6.2.1)

• Mechanical treatment
• Solvent cleaning
• Chemical treatment
• Anodic treatments

Surface Preparation Guidelines (Clause 6.3.3.1)

• Degrease by solvent wipe before applying wash or etching primers.
• Use etching solutions (acidic or mordants) but avoid copper-based mordants to prevent corrosion.
• Rinse thoroughly after etching to remove acids/salts.
• Weathering galvanized steel until bright spangles disappear may eliminate need for degreasing.
• For small areas, abrasion with emery cloth + solvent washing can be used.

Summary Table: Pretreated Surface Maintenance

Important Considerations (Clause 3.1)

• Identify metal/alloy type.
• Assess surface condition and contaminants.
• Consider environmental exposure.
• Know previous finishes for repainting.

flowchart TD
    A[Inspect Surface] --> B{Damaged?}
    B -- Yes --> C[Degrease with Solvent]
    C --> D[Remove Corrosion Products]
    D --> E[Apply Wash/Etching Primer]
    E --> F[Apply Primer, Putty, Finish Coats]
    B -- No --> G[No Action or Routine Maintenance]

This ensures longevity and corrosion