IS 2932: The Code of Practice for Painting of Ships and Marine Structures

Introduction to IS 2932

The IS 2932: Code of Practice for Painting of Ships and Marine Structures is designed to ensure the durability, corrosion resistance, and aesthetic appeal of ships and marine structures. The standard is particularly important for maintaining the integrity of ships, offshore platforms, and related structures exposed to harsh marine environments.

Detailed Overview of IS 2932:

1. Introduction

• Objective: The main objective is to provide a set of guidelines for the proper selection and application of protective coatings to prevent corrosion, biofouling, and degradation caused by seawater, UV radiation, and extreme weather conditions.

• Applicability: This standard applies to both new constructions and maintenance or repair activities for marine structures and ships.

2. Surface Preparation

• Cleanliness Standards: The standard specifies cleanliness levels for various types of surfaces before the application of paint, such as:

• Abrasive Blasting: Achieving a specified cleanliness level such as SA 2½ (ISO standard) or white metal finish for optimal adhesion of paints.

• Power Tool Cleaning: Used for removing rust, old paint, and loose particles on surfaces not suitable for blasting.

• Water Jetting: High-pressure water jetting to remove salt and other contaminants.

• Surface Profile: The roughness or texture of the surface after cleaning, which should be compatible with the type of coating being applied to ensure optimal bonding.

3. Paint Systems and Types

• Primer Coats: Primer coatings are essential in preventing rust and improving adhesion between the substrate and subsequent coats. Typically, zinc-rich primers or epoxy-based primers are recommended.

• Intermediate Coats: Used to build up the coating system and add additional protection. These coatings are typically thicker and help in preventing water ingress.

• Top Coats: The final layer is meant to provide both protection and aesthetic appeal. High-performance coatings like polyurethane or acrylic systems are often used for UV resistance and durability.

• Anti-fouling Coatings: In addition to standard coatings, anti-fouling paints are often applied to the hull of ships to prevent marine organisms like barnacles and algae from adhering to the surface. Copper-based paints or biocidal coatings are commonly used for this purpose.

4. Material and Paint Selection

• Marine Grade Paints: The standard covers specific marine-grade paints that are resistant to seawater, brine, and oil spills. These paints include:

• Epoxy Coatings: Known for their high resistance to chemical corrosion, commonly used in ballast tanks and underwater hull areas.

• Polyurethane Paints: Provide excellent UV resistance and weathering performance, typically used for superstructures and exposed areas.

• Chlorinated Rubber Paints: Offers resistance to water, weather, and chemicals, often applied to steel surfaces in damp environments.

• Coal Tar Epoxy: A thick and highly resistant coating, often used in ballast tanks and submerged areas due to its exceptional water and chemical resistance.

5. Environmental Conditions for Painting

• Temperature: There are restrictions on painting under extreme temperatures. Optimal conditions range between 10°C to 40°C.

• Humidity: Humidity plays a crucial role in paint curing. The relative humidity should not exceed 85% during the application of paints.

• Dew Point: The surface temperature should be at least 3°C above the dew point to avoid moisture condensation, which could affect the adhesion of the coating.

6. Application Methods

• Spray Application: Airless or conventional spray methods are commonly used for large surfaces. This ensures uniform application of paints and coatings.

• Brush Application: Used for small areas, edges, or areas with complex geometries where spraying is not effective.

• Roller Application: Suitable for applying even layers on flat surfaces and for touch-up jobs.

7. Film Thickness and Coverage

• Dry Film Thickness (DFT): The code specifies minimum and maximum DFT for various types of coatings. A higher DFT generally improves protection but can lead to cracking if excessive.

• Wet Film Thickness (WFT): Guidelines on applying paint to ensure the correct thickness once it dries. Wet film gauges are often used during application to ensure compliance.

8. Inspection and Quality Control

• Adhesion Tests: Adhesion is a critical factor for long-term durability. The code specifies pull-off tests, cross-cut tests, and other methods for verifying proper adhesion.

• Thickness Testing: Tools like ultrasonic thickness gauges are used to verify that the dry film thickness matches the specified value.

• Holiday Detection: This involves detecting pinholes or holidays in the coating, which could expose the underlying surface to corrosion.

9. Maintenance and Recoating

• Periodic Inspection: Ships and marine structures require regular inspections for signs of wear, corrosion, or biofouling. Maintenance protocols should be set up for regular repainting and spot repairs.

• Repair of Damaged Coatings: Guidelines for the preparation and recoating of damaged areas, ensuring seamless integration with existing coatings.

10. Special Considerations

• Cathodic Protection: In some cases, the code may recommend using cathodic protection systems along with paint systems to prevent corrosion, especially in submerged areas.

• Biofouling and Anti-fouling Standards: The use of environmentally compliant anti-fouling paints and methods that minimize the environmental impact of the coatings.

11. Advantages of Following IS 2932

• Extended Lifespan: Proper application of marine coatings ensures the longevity of ships and structures.

• Corrosion Protection: Adherence to the standard significantly reduces the chances of rusting and corrosion, leading to fewer repairs.

• Environmental Protection: The use of approved and regulated coatings helps minimize harm to marine ecosystems.

• Cost Savings: With proper coatings and periodic maintenance, long-term maintenance costs are reduced as the need for major repairs diminishes.

12. Safety Measures

• Handling Paint Materials: Specific safety measures regarding the handling, mixing, and storage of paint materials.

• Ventilation: Ensuring proper ventilation when working in confined spaces like ship interiors or tanks.

• Protective Equipment: Use of personal protective equipment (PPE), including respirators, gloves, and protective clothing when applying paints, particularly in enclosed environments.

These guidelines ensure that marine structures remain protected from the harsh marine environment, leading to safer operations, reduced maintenance costs, and better environmental compliance. The actual IS 2932 document can be acquired from the Bureau of Indian Standards (BIS) for a more comprehensive set of technical details and specifications.