Code of practice for the painting of nonferrous metals in buildings, Part 1: Pretreatment
1968 Edition

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

This section details the framework for planning and performing painting on non-ferrous metals, focusing on:

• Metal or Alloy Identification: Determining the exact type.
• Surface Status: Assessment for scale, rust, moisture, grease, salts.
• Operating Environment: Assessment of atmospheric or working conditions impacting paint performance.
• Prior Coating Information: Critical for maintenance repainting.

Key Specifications & Notes

Factory Pretreatment Techniques (Clause 6.2.1)

• Mechanical methods such as abrasion and blasting
• Solvent-based cleaning to remove oils and greases
• Chemical cleaning involving acid or alkaline solutions
• Electrochemical anodic surface treatments

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

This systematic methodology ensures durable paint application on non-ferrous metals in line with IS 2524 Part 1.

Key Terminology & Definitions in IS 2524 Part 1 (1968)

• Painting Terms: Follow definitions from IS 1303:1963, including primer, enamel, undercoat, etc.

• Essential Painting Information (Clause 3.1):

  • Type of metal or alloy.
  • Condition of the surface including contaminants.
  • Service environment impacting the coating.
  • Details of any existing finishes for repainting.

• Factory Pretreatment Details (Clause 6.2.1):

  • Mechanical surface preparation (abrasion, blasting).
  • Solvent cleaning for grease and oils.
  • Chemical treatments (acidic or alkaline cleaning).
  • Anodic (electrochemical) treatment for surface modification.

Summary Table: Factory Pretreatment Options

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

Note: Refer to IS 1303:1963 for comprehensive painting terminology.

Information Required for Painting Non-Ferrous Metals as per IS 2524 Part 1

Highlights from Clause 3.1:

• Metal/Alloy Identification: Specify exact type.
• Surface Condition: Check for scale, rust, moisture, grease, salts.
• Service Environment: Understand environmental factors such as humidity, chemicals, and temperature.
• Previous Coating: Document for maintenance repainting.

Surface Preparation Guidelines (Clause 3.3):

• For galvanized steel or zinc sheets, degreasing is mandatory.
• Surfaces should be pretreated or weathered (about 3 months in clean air) to ensure adhesion.
• Alternatively, use specially formulated primers suited for galvanized surfaces.

Rounding Off (Clause 0.6):

• Follow IS 2-1960 for rounding test results, maintaining required significant digits.

Summary Table: Painting Information and Surface Prep

References:

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

flowchart TD
    A[Begin Painting Process] --> B{Identify Metal Type}
    B --> C[Examine Surface Condition]
    C --> D{Contaminants Present?}
    D -- Yes --> E[Clean Surface: Remove rust, grease, salts]
    D -- No --> F[Proceed to Next Step]
    E --> F
    F --> G{Is Metal Galvanized Steel or Zinc?}
    G -- Yes --> H[Degrease and Pretreat or Weather 3 Months or Use Special Primer]
    G -- No --> I[Standard Painting Procedure]
    H --> J[Apply Paint]
    I --> J
    J --> K[Completion]

This procedure ensures optimal paint adhesion and durability.

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

Main Points from Clause 4.1:

• Accessibility: Design surfaces to be easily reachable for painting and priming.
• Surface Conditions: Ensure surfaces promote strong adhesion and provide maximum protection.
• Durability: Design to extend paint life and resist environmental effects.

Influential Factors (Clause 3.1):

• Metal type influences paint selection.
• Surface must be free of scale, rust, moisture, grease, salts.
• Environmental exposure (humidity, chemicals, temperature) must be considered.
• Knowledge of previous coatings assists maintenance.

Pretreatment Approaches (Clause 6.2.1):

Practical Design Tips:

• Avoid areas that trap moisture.
• Create smooth and cleanable surfaces.
• Use primers compatible with the metal.
• Plan for easy maintenance and repainting.

Standards and References:

• Consult IS 1303-1963 for painting terms.
• Follow rounding guidelines in IS 2524.

flowchart LR
    A[Design Surface] --> B[Ensure Accessibility]
    B --> C[Prepare Surface]
    C --> D{Choose Pretreatment}
    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 Planning]

This ensures the longevity and effectiveness of painting on non-ferrous metals.

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

1. Metal Characteristics (Clause 3.1):

• Zinc, copper, lead, pure aluminum, and aluminum alloys vary in corrosion behavior and paint requirements.
• Surfaces must be free from scale, rust, moisture, grease, and salts before painting.
• Environmental exposure influences paint selection.
• Previous finishes are important for repainting.

2. Painting Protocols (Clause 5.2.6):

• Protective coatings like sprayed zinc are porous and rough, needing different pretreatment compared to solid sheets.
• Unpainted use is limited when metals protect steel or iron.

3. General Painting Guidelines

4. Pretreatment Overview

• Thorough cleaning.
• Remove contaminants.
• Utilize primers suitable for each metal.
• Ensure surfaces are dry before painting.

Example: Aluminium Pretreatment Steps

1. Degrease.
2. Remove oxides chemically or mechanically.
3. Apply a compatible primer, such as chromate-based.
4. Apply paint system as recommended.

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

Note: IS 2524 Part 1 covers pretreatment; Part 2 contains painting schedules for comprehensive guidance.

Surface Preparation and Pretreatment Overview (IS 2524 Part 1)

Core Pretreatment Methods (Clause 6.2.1):

• Mechanical: Remove rust and scale via abrasion.
• Solvent Cleaning: Remove oils and contaminants.
• Chemical: Use chromate or etching solutions.
• Anodic: Electrochemical surface modification.

Factory Pretreatment (Clause 6.3.2):

• Solvent cleaning is mandatory before any further treatment.
• Chromate treatment involves dipping or spraying with dilute chromic acid to form a thin protective layer enhancing corrosion resistance and adhesion.
• Aqueous chromic organic treatment applies chromium-containing resins by rollers or dipping.
• Etching or wash primers use acid or mordant solutions; thorough rinsing is essential to remove residues.

Surface Repairs (Clause 6.2.2.2):

• Inspect factory-pretreated surfaces.
• Degrease damaged spots.
• Remove corrosion products.
• Touch up with wash or etching primers.
• Apply primer, filler, and finish coats as needed.

Untreated Surface Preparation (Clause 6.3.3.1):

• Thorough degreasing.
• Apply wash or etching primers.
• Avoid copper-containing mordants.
• Rinse well after etching.
• Weathered galvanized surfaces may be painted without degreasing.
• Small areas can be abraded with emery cloth followed by solvent cleaning.

Treatment Summary Table

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

This ensures proper adhesion and longevity of paint on non-ferrous metals.

General Principles of Pretreatment (IS 2524 Part 1)

Key Points:

• Pretreatment is divided into:

  • Factory Pretreatment: Performed in controlled environments.
  • Field (On-site) Pretreatment: Conducted at installation locations.

• Focus on on-site preparation includes cleaning and conditioning before protective coatings.

Guidelines:

• Eliminate dirt, oil, grease, rust, and mill scale.
• Cleaning methods include solvent cleaning, abrasive blasting, and acid pickling.
• Achieve a surface roughness profile of approximately 50–75 microns for optimal coating adhesion.

Typical Process Flow:

flowchart LR
    A[Surface Inspection] --> B[Select Cleaning Method]
    B --> C[Perform Cleaning]
    C --> D[Check Surface Profile]
    D --> E[Apply Primer or Coating]

Critical Specifications

Note: Refer to IS 2524 Part 1 for specific substrate pretreatment and comply with coating manufacturer guidelines.

Pretreatment of Aluminium and Its Alloys (IS 2524 Part 1 Clauses 6.2.1.3 & 6.2.2.1)

Chemical Treatments (Clause 6.2.1.3):

• Alkaline Etching: Using caustic soda to remove oxide layers, followed by nitric or phosphoric acid; requires subsequent conversion coating.
• Sulphuric-Chromic Acid Etching: Produces a passive surface suitable for mild exposures and clear finishes.
• Phosphoric Acid Cleaners: Apply thin phosphate films to promote adhesion under mild conditions.
• Acid Fluoride Deoxidizer: Mix of nitric, sulphuric, chromic acids with fluoride at 35–55°C for uniform surface.
• Amorphous Phosphate Treatments: Immersion or spray with phosphoric, chromic, and hydrofluoric acids; provides corrosion resistance and paint durability.
• Carbonate Chromate Treatment: Hot sodium carbonate and potassium chromate solution forms thin conversion coatings.
• Amorphous Chromate Treatment: Chromic acid with fluoride accelerators creating golden to brown oxide coatings, enhancing corrosion resistance.
• Etching or Wash Primers: Acid-bound resin films to improve paint adhesion.

Surface Preparation for Untreated or Temporarily Protected Surfaces (Clause 6.2.2.1):

• Remove temporary protective films with solvents.
• Eliminate rolling lubricants using solvents and abrasive papers.
• Remove welding flux residues with 10% formic acid solutions.
• Mechanically roughen heat-hardened alloys and degrease.
• Use stainless steel brushes to remove corrosion; avoid steel wire brushes.
• Chemical corrosion removal requires inhibited acids and thorough rinsing.
• Cast alloys generally need only degreasing before painting.

Chemical Treatment Summary

[...Additional treatments continue as per full standard...]

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

Summary of Clauses 6.3.1 to 6.3.3.1 and 5.4:

• Degreasing: Essential to remove oils, greases, and contaminants before painting (solvent cleaning per 6.2.1.2).
• Chromate Treatment: Dipping or spraying in dilute chromic acid to form a thin amorphous chromate layer, enhancing corrosion resistance and adhesion.
• Aqueous Chromic Organic Treatment: Application via roller, dip, or squeeze rolls producing a corrosion-resistant film.
• Etching or Wash Primers: Acid or mordant-based treatments; copper-containing mordants should be avoided.
• Weathering: Allow natural weathering until bright spangles fade; then painting can be done without degreasing.
• Mechanical Abrasion: Emery cloth combined with solvent cleaning for small repairs to create a matte surface.
• Corrosion Considerations: Paint in damp, polluted, or industrial atmospheres; coating life is proportional to zinc weight.

Pretreatment Methods Overview

flowchart TD
    A[New Zinc/Galvanized Steel] --> B[Degreasing with Solvent]
    B --> C{Select Treatment}
    C -->|Chemical| D[Etching / Wash Primer]
    C -->|Weathering| E[Allow Surface to Weather]
    C -->|Mechanical| F[Abrade Small Areas]
    D & E & F --> G[Apply Paint System]

This ensures effective adhesion and corrosion protection.

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

Key Requirements:

• Cleaning: Use organic solvents to remove grease and dirt.
• Remove copper dust after mechanical abrasion to prevent verdigris staining.
• Surface Roughening: Lightly abrade with fine abrasive paper to improve adhesion.
• Primer Application: One coat of etching primer to seal the surface and enhance paint bonding.
• Factory Electroplating: Electro-deposited tin coatings are recommended for improved paint preparation.
• Conversion Coatings: For outdoor or corrosive environments, apply conversion coatings (e.g., dichromate) to improve protection and adhesion.

Pretreatment Summary Table

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

Proper surface preparation is critical to avoid paint failure and staining.

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

Summary of Clauses:

• Cadmium requires pretreatment similar to zinc but does not need weathering.
• Factory pretreatment includes mechanical, solvent, chemical, and anodic treatments.
• Solvent cleaning to remove oils and greases is mandatory before further surface treatments.

Recommended Pretreatment Methods:

Pretreatment Workflow

flowchart TD
    A[Cadmium Coated Steel] --> B[Mechanical Treatment]
    B --> C[Solvent Cleaning]
    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 is not necessary for cadmium, unlike zinc.

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

Key Points:

• Terne Plate (Lead-Tin Alloy): Avoid use of graphite in primers, which can impair adhesion.

• Use etching treatments if adhesion problems occur.

• Lead: New surfaces should be pretreated with an etching primer or alternatively treated with about 20% ortho-phosphoric acid solution followed by thorough washing and drying.

• Protection from Acidic Woods: Avoid rainwater runoff from acidic hardwoods like oak or chestnut onto metal surfaces to prevent corrosion.

• Factory Pretreatment: Includes solvent cleaning, chromate treatments, aqueous chromic organic treatments, and etching or wash primers.

Summary Table

flowchart TD
    A[New Lead or Terne Metal] --> B{Check Surface Cleanliness}
    B -->|Grease/Oil Present| C[Solvent Cleaning]
    B -->|Clean| D{Select Pretreatment}
    D --> E[Apply Etching Primer]
    D --> F[Chromate or Organic Treatments]
    E & F --> G[Painting]

Ensures durable coatings on lead and terne metals.

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

Treatment Methods:

• Mechanical abrasion suitable for mild indoor environments.
• Solvent cleaning to remove oils and contaminants.
• Alkaline and acid cleaning as initial steps without providing protective coatings.
• Conversion coating using dichromate methods essential for outdoor or severe corrosion environments.
• Anodic treatments serving both cleaning and conversion coating functions.

Key Notes:

• Magnesium forms an alkaline oxidation film which needs careful preparation before painting.
• Corrosion is slower indoors but rapid outdoors, especially in chloride environments.
• Painting combined with chemical pretreatment offers optimal protection.

Pretreatment Summary

Conversion Coating Procedure

1. Surface cleaning (mechanical and solvent).
2. Alkaline or acid cleaning.
3. Dip in dichromate solution.
4. Rinse and dry.
5. Paint application.

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

For best results, use conversion or anodic treatments prior to painting magnesium alloys in outdoor or aggressive environments.

Pretreatment of Tin (IS 2524 Part 1 - 1968)

• Objective: Achieve good paint adhesion through thorough degreasing and surface roughening.

Factory Pretreatment Methods (Clause 6.2.1):

1. Mechanical abrasion to roughen surface.
2. Solvent cleaning to remove oils and contaminants.
3. Chemical treatments including chromate and etching.
4. Anodic treatment to modify surface electrochemically.

Specific Treatments (Clause 6.3.2):

• Solvent cleaning mandatory before other treatments.
• Chromate treatment via dip or spray with dilute chromic acid to enhance corrosion resistance and adhesion.
• Aqueous chromic organic treatments applied by dip or roller to provide protection.
• Etching or wash primers to activate surface for painting.

Summary Table of Pretreatment Steps

flowchart TD
    A[Tin Surface] --> B[Degreasing]
    B --> C[Surface Roughening]
    C --> D{Select Treatment}
    D -->|Chromate| E[Chromate Dip/Spray]
    D -->|Chromic Organic| F[Aqueous Chromic Resin]
    D -->|Etching| G[Etching or Wash Primer]
    E & F & G --> H[Paint Application]

Note: Avoid graphite in primers for terne plates as per specifications.

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

Key Actions (Clause 6.2.2.2):

• Conduct thorough inspection of pretreated and primed surfaces.
• Degrease damaged areas with solvent swabbing.
• Remove all corrosion and rust.
• Touch up affected areas using wash or etching primers or suitable chemical treatments.
• Apply primer, putty, and finish coats to restore protective layers.

Factory Pretreatment Methods (Clause 6.2.1):

• Mechanical abrasion
• Solvent cleaning
• Chemical treatments
• Anodic treatments

Surface Preparation Guidelines (Clause 6.3.3.1):

• Clean with solvent before applying etching or wash primers.
• Use acid or mordant etching solutions, avoiding copper-containing mordants.
• Rinse thoroughly after etching to eliminate residues.
• Weather galvanized steel until spangles dull for better paint adhesion.
• Use emery cloth and solvent cleaning for small repairs.

Maintenance Summary Table

Considerations (Clause 3.1):

• Identify metal or alloy.
• Assess surface condition and contaminants.
• Understand environmental exposures.
• Document previous coatings for maintenance.

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

This process helps ensure the longevity and protection of painted metal surfaces.