Aux 2 Unit 16 Q6

The application of protective coatings to a vessel’s hull serves several essential purposes to ensure the vessel’s longevity, efficiency, and safety. The key applications of these coatings are:

1. Corrosion Protection

• Purpose: The hull of a ship is constantly exposed to seawater, which is highly corrosive. Protective coatings act as a barrier between the hull and the seawater, preventing the oxidation and degradation of the metal.
• Types of Coatings: Epoxy and polyurethane-based coatings are commonly used for corrosion resistance.

2. Anti-fouling Protection

• Purpose: Marine organisms such as barnacles, algae, and mussels tend to attach themselves to the hull, causing increased drag and reducing the vessel’s speed and fuel efficiency. Anti-fouling coatings prevent these organisms from adhering to the hull.
• Types of Coatings: Anti-fouling paints often contain biocides, such as copper compounds, which deter marine growth.

3. Improved Fuel Efficiency

• Purpose: A smooth, clean hull reduces drag as the vessel moves through water. Coatings help maintain the smoothness of the hull by preventing corrosion and fouling, which would otherwise increase resistance and fuel consumption.
• Hydrodynamic Coatings: These specialized coatings reduce the friction between the hull and water, optimizing the ship’s hydrodynamic performance and improving fuel efficiency.

4. Structural Integrity and Longevity

• Purpose: The hull experiences mechanical stress from the vessel’s movement and environmental forces. Coatings protect the structural materials from deterioration, thus maintaining the integrity and extending the life of the ship.
• Heavy-Duty Coatings: Thicker, high-durability coatings (e.g., epoxy) provide resistance against mechanical wear, impact, and stress on the hull.

5. Cathodic Protection Integration

• Purpose: Coatings are often used alongside cathodic protection systems (e.g., sacrificial anodes) to offer dual protection against corrosion. The coating minimizes the area that the cathodic protection system must cover, reducing overall corrosion rates.

6. Aesthetic Appeal

• Purpose: While functional in nature, protective coatings also contribute to the visual appearance of the vessel. A well-coated hull can look aesthetically pleasing and professionally maintained, which is especially important for commercial and passenger ships.

7. Safety

• Purpose: Coatings help ensure the safety of the vessel by reducing the likelihood of structural failures due to corrosion or degradation. This is especially important in critical areas such as ballast tanks, the keel, and underwater hull sections.

Protective coatings on a vessel’s hull are essential for reducing maintenance costs, enhancing performance, and ensuring long-term seaworthiness. They are applied in layers, each with a specific function (e.g., primer, anti-corrosive, anti-fouling), and play a crucial role in the overall maintenance strategy of any ship.

When applying protective coatings to a vessel’s hull, the coatings are expected to perform several critical functions to ensure the ship’s structural integrity, longevity, and operational efficiency. These functions include:

1. Corrosion Protection

• Function: One of the primary roles of a hull coating is to act as a barrier against seawater, which is highly corrosive due to its salt content. The coating should prevent water, oxygen, and salts from coming into direct contact with the ship’s metal structure, reducing oxidation and metal deterioration.
• Requirement: The coating must be durable, resistant to water penetration, and chemically stable in marine environments.

2. Anti-fouling

• Function: The coating should prevent marine organisms such as barnacles, algae, and mollusks from attaching to the hull. These organisms increase drag, which negatively impacts the ship’s speed, fuel consumption, and overall efficiency.
• Requirement: Anti-fouling coatings typically contain biocides (e.g., copper or organic compounds) that deter the attachment and growth of marine life on the hull.

3. Abrasion and Impact Resistance

• Function: The coating should protect the hull from mechanical damage caused by the ship’s contact with debris, ice, or dock structures. It must resist abrasion, impacts, and erosion to maintain the hull’s structural integrity.
• Requirement: The coating needs to be tough, flexible, and capable of withstanding mechanical stress without chipping or flaking.

4. Smoothness and Reduced Friction

• Function: The coating should create a smooth surface that reduces hydrodynamic drag, allowing the ship to move through water more efficiently. A smooth hull leads to improved fuel efficiency and reduced operational costs.
• Requirement: Specialized coatings, such as silicone-based hydrodynamic coatings, can further reduce the friction between the hull and the water, optimizing the vessel’s speed and fuel consumption.

5. Chemical Resistance

• Function: The coating should protect the hull from exposure to chemicals, oils, and other potentially harmful substances encountered in marine environments (e.g., ballast water, spills, and cargo residue).
• Requirement: The coating needs to be resistant to acids, alkalis, hydrocarbons, and other chemicals that could degrade or compromise the hull’s material.

6. Flexibility

• Function: Ships are subject to various stresses, including bending, flexing, and torsional forces. The coating must be flexible enough to accommodate these stresses without cracking, peeling, or losing its protective properties.
• Requirement: Elastic or flexible coatings are necessary to ensure that they remain intact even as the hull deforms slightly due to load changes or wave impacts.

7. Long-Term Durability

• Function: The coating should provide long-term protection, minimizing the need for frequent maintenance and dry-docking. A durable coating ensures that the ship operates efficiently for extended periods between maintenance cycles.
• Requirement: The coating should be resistant to wear and environmental degradation over time, maintaining its protective qualities even under harsh marine conditions.

8. Cathodic Protection Compatibility

• Function: The coating should work in conjunction with cathodic protection systems, such as sacrificial anodes, to further reduce the rate of corrosion. It reduces the area exposed to seawater, making the cathodic system more efficient.
• Requirement: The coating must be electrically insulating in areas where cathodic protection is used to ensure proper functioning of the system.

9. Environmental Safety

• Function: The coating should not negatively impact the marine environment. While it needs to protect the hull, it should also comply with international environmental regulations, such as those governing biocides and harmful chemicals in anti-fouling paints.
• Requirement: Environmentally friendly or low-toxicity coatings are increasingly important, with a shift toward alternatives that provide protection without damaging marine ecosystems.

In summary, protective coatings applied to a vessel’s hull must perform multiple functions—corrosion prevention, anti-fouling, impact resistance, hydrodynamic efficiency, and chemical durability—while ensuring the ship remains operationally efficient and compliant with environmental standards.

The legislation that applies to certain coatings, particularly anti-fouling and protective coatings for vessels, is primarily driven by international regulations aimed at protecting the marine environment, human health, and promoting safety standards. The key legislation and the certification required to comply with it include:

1. International Convention on the Control of Harmful Anti-fouling Systems on Ships (AFS Convention)

• Overview: This is a globally binding regulation under the International Maritime Organization (IMO) that was adopted in 2001 and entered into force in 2008. The AFS Convention prohibits the use of harmful substances in anti-fouling paints, particularly tributyltin (TBT), which was previously a widely used biocide but had toxic effects on marine organisms.
• Requirements: Ships are prohibited from applying or re-applying harmful anti-fouling systems containing substances like TBT and other harmful organotin compounds. Vessels must use anti-fouling coatings that comply with approved alternatives under the AFS Convention.
• Certification:
  • International Anti-Fouling System Certificate (IAFSC): Ships of 400 gross tonnage and above engaged in international voyages must carry an IAFSC, issued by the flag state, verifying compliance with the AFS Convention.
  • Declaration on Anti-Fouling Systems: For ships below 400 gross tonnage, a declaration signed by the owner or authorized agent may be required, certifying the application of compliant anti-fouling coatings.

2. Ballast Water Management Convention (BWM Convention)

• Overview: Though not directly focused on coatings, the BWM Convention, adopted by the IMO and in force since 2017, can influence the types of coatings applied inside ballast tanks. Protective coatings may be required to maintain ballast tanks free of invasive species, preventing contamination and improving the tank’s durability.
• Certification: Ballast tanks may need to be coated with systems that comply with BWM standards. Ships need certification under the BWM Convention for ballast water treatment, and certain coatings may be part of this system’s compliance.

3. IMO Performance Standards for Protective Coatings (PSPC)

• Overview: Adopted by the IMO under SOLAS (International Convention for the Safety of Life at Sea), the Performance Standards for Protective Coatings set out specific requirements for the application of protective coatings, particularly in water ballast tanks and crude oil tanks.
  • Water Ballast Tanks: SOLAS regulations mandate the use of protective coatings in the ballast water tanks of new ships to prevent corrosion and structural failure.
  • Crude Oil Tanks: Similar requirements exist for cargo oil tanks in crude oil tankers.
• Certification:
  • Type Approval Certificate: Protective coatings applied to ballast tanks and oil tanks must meet PSPC requirements and typically need to be type-approved by a recognized classification society. Coatings should comply with standards such as ISO 12944 or NORSOK M-501 for corrosion protection.
  • Coating Technical File (CTF): The shipbuilder must maintain a CTF that documents all information related to the coating application, inspection, and compliance with PSPC. The file is subject to review by classification societies.

4. REACH Regulation (EU Regulation on Registration, Evaluation, Authorisation, and Restriction of Chemicals)

• Overview: REACH is a European Union regulation that governs the use of chemicals, including substances used in protective coatings and anti-fouling paints. The regulation ensures that chemical substances are tested, evaluated, and authorized for safe use in industrial and marine applications.
• Requirements: Coating manufacturers must comply with REACH, which may restrict or ban the use of certain hazardous chemicals in paints and coatings.
• Certification: Certification of compliance with REACH is necessary for any coatings being applied within the European Union. Shipowners and manufacturers must ensure that the products used are certified and registered under REACH.

5. ISO Standards for Marine Coatings

• Overview: The International Organization for Standardization (ISO) sets technical standards for protective coatings applied to ships. These standards ensure that coatings meet performance, durability, and safety criteria.
• Notable Standards:
  • ISO 12944: This standard relates to corrosion protection of steel structures by protective paint systems, which is applicable to vessels’ hulls.
  • ISO 20340: Focuses on coatings used in offshore and marine environments for long-term protection.
• Certification: Manufacturers of protective coatings and shipyards must ensure that the coatings used are compliant with the relevant ISO standards. Certification of compliance with ISO standards is generally obtained through testing and verification by classification societies.

6. Classification Society Rules

• Overview: Classification societies such as Lloyd’s Register, DNV, ABS, and Bureau Veritas have their own rules and guidelines regarding protective coatings for ships. These rules are aligned with IMO conventions and ISO standards.
• Certification:
  • Type Approval: Coating systems must be type-approved by classification societies to ensure they meet the required performance standards for use in specific areas like ballast tanks, cargo tanks, and underwater hull sections.
  • Coating Inspection and Certification: Classification societies inspect and certify the proper application of protective coatings during ship construction and maintenance to ensure compliance with safety and durability standards.

In summary, protective coatings on a vessel’s hull must comply with international regulations such as the IMO’s AFS Convention and PSPC under SOLAS, as well as regional regulations like the EU’s REACH. Certification such as the International Anti-Fouling System Certificate, type approvals from classification societies, and compliance with ISO standards are required to demonstrate adherence to these laws.

The process of re-coating the hull of a vessel in drydock involves several key steps to ensure that the protective coatings are applied effectively, providing long-lasting protection against corrosion, fouling, and other environmental hazards. Below is an outline of the process:

1. Preparation for Drydocking

• Initial Inspection: Before entering drydock, a thorough inspection of the vessel’s hull is conducted to assess the condition of the existing coating, check for any damage, and determine the necessary work scope.
• Docking Plan: A docking plan is prepared, ensuring that the vessel is properly supported on keel blocks or dock pillars to avoid any structural stress.

2. Drydocking the Vessel

• Mooring and Positioning: The vessel is brought into the drydock and positioned over keel blocks, ensuring the vessel is centered and supported correctly.
• Pumping Out Water: Once the vessel is in position, the drydock is sealed, and the water is pumped out, leaving the hull exposed for inspection and work.

3. Surface Preparation

• Cleaning the Hull: The hull is cleaned to remove marine growth, fouling, and any loose or degraded paint. High-pressure water jetting or hydro-blasting is commonly used to clean the surface thoroughly.
• Abrasive Blasting: For proper adhesion of the new coating, the old coating and corrosion are often removed using abrasive blasting (e.g., sandblasting or grit blasting). This creates a rough surface that promotes better bonding of the new coating. The level of surface cleanliness is usually measured according to standards such as the Society for Protective Coatings (SSPC) or ISO 8501.
• Surface Inspection: After cleaning and blasting, the hull surface is inspected to ensure it meets the necessary cleanliness and roughness standards for coating application. Any remaining rust or contaminants must be removed before proceeding.

4. Repairing and Fairing

• Hull Repairs: If the hull has sustained any damage, such as dents, cracks, or corrosion, these areas are repaired before coating. Welding and metalwork may be required to restore the hull’s integrity.
• Fairing Compound Application: Fairing compound (a thickened epoxy) may be applied to smooth out any irregularities on the hull surface and create an even surface for the coating application.

5. Primer Application

• Purpose: A primer is applied as the first layer to promote adhesion of the subsequent coats and to provide initial protection against corrosion.
• Application Method: The primer is typically applied using airless spray systems, although brushes and rollers can be used for smaller areas or touch-ups.
• Curing Time: Sufficient curing time is allowed for the primer to dry before applying the next layers, following the manufacturer’s recommendations for drying times.

6. Anti-Corrosive Coating Application

• Purpose: This layer provides additional protection against corrosion caused by seawater and harsh marine environments. It acts as a barrier to prevent rust and degradation of the hull.
• Coating Type: Typically, epoxy-based coatings are used for their excellent corrosion resistance.
• Multiple Layers: Several layers of anti-corrosive coating may be applied, with each layer allowed to cure according to the manufacturer’s specifications.

7. Anti-Fouling Coating Application

• Purpose: Anti-fouling coatings prevent marine organisms (such as barnacles and algae) from attaching to the hull, which reduces drag and improves fuel efficiency.
• Coating Type: Anti-fouling paints, often containing biocides, are applied in multiple layers depending on the vessel’s operational profile and the required longevity of the coating.
• Application Method: Similar to previous coatings, airless spray systems are commonly used to ensure even and efficient application.
• Curing: Adequate curing time is provided between each coat and before the vessel is re-floated.

8. Final Inspection

• Coating Thickness Measurement: After the coatings are applied, the thickness of each layer is measured using a dry film thickness (DFT) gauge to ensure compliance with specified standards and manufacturer recommendations.
• Adhesion Testing: Adhesion tests may be conducted to verify that the coating has properly bonded to the hull surface.
• Visual Inspection: A thorough inspection is performed to ensure uniformity of the coating, check for defects (e.g., pinholes, blistering), and ensure that all areas are adequately protected.

9. Markings and Final Touch-ups

• Hull Markings: Ship markings, such as draft marks, load line marks, and vessel identification, are repainted as needed.
• Touch-ups: Any areas that require touch-up or where the coating may have been damaged during the application process are repaired before flooding the dock.

10. Floating the Vessel

• Re-flooding the Dock: After the coatings are fully cured and all inspections have been completed, the drydock is refilled with water.
• Vessel Repositioning: The vessel is carefully floated off the keel blocks and repositioned to allow it to be towed or sailed out of the dock.

11. Final Sea Trials and Monitoring

• Operational Tests: Once the vessel is back in the water, operational tests and sea trials may be conducted to ensure the vessel is functioning properly and that the coatings are performing as expected.
• Ongoing Monitoring: The condition of the hull and its coatings should be periodically monitored throughout the vessel’s operational life to schedule future maintenance and drydocking as needed.

Re-coating a vessel’s hull in drydock is a complex process that requires careful surface preparation, the application of multiple specialized coatings, and adherence to manufacturer specifications to ensure that the coatings provide optimal protection and performance for the vessel.