Underwater Hull Underwater Hull Overview

The underwater hull area is subjected to the harsh corrosive environment of seawater and marine growth. Coatings extending from the keel to the boottop are coated with an anti-corrosive primer and topcoated with an anti-fouling coating system.

Maintenance Procedures
  • Hull coating touch-ups, repair, and cleanings - U.S. Navy and commercial dive activities
  • Major repairs and refurbishment - dry dock during maintenance availabilities
  • The U.S. Navy's underwater hull coating systems are designed to provide a service life of 3-12 years, depending on the desired durability.

Surface Preparation Requirements

  • Near White Metal Blast - NACE 2 / SSPC-SP10
  • Waterjetting – NACE 5 / SSPC-SP 12 Condition WJ-2L

Product General Description

  • Primer:    Anti Corrosive Epoxy
  • Topcoat: Copper Ablative Anti-fouling

Approved Coatings and Applicable Coating Specifications

  • MIL-PRF-24647 - Military specification and related documents
  • NAVSEA Standard Item 009-32 Applicable to surface ship preservation is Standard Item 009-32, "Cleaning and Painting Requirements." It contains cleanliness, surface preparation, and coating application requirements, along with complete system application instructions for each product approved for underwater hull preservation.
  • NAVSEA Approved Advanced Coating and Covering Messages - Additional approved coatings

Coating Application Process

Preservation Process Instructions (PPIs) document the latest requirements and procedures for coating applications, and contain information on the following:
  • Cleaning
  • Coating application
  • Quality requirements
  • Check points
  • QA inspection

Preservation Processs Instructions

Key Application Requirements

  • Key Application Requirements - are to be followed during preservation practices and are referenced in a variety of document sources. Some of the requirements referenced include environmental and quality assurance monitoring such as dehumidification, temperature, surface profile measurements and coating thickness measurements.

Ship’s Force - Repair Requirements

Ship's force personnel do little underwater hull repair work. Normally, coatings are inspected by divers prior to maintenance availabilities, and if warranted, repair and replacement is conducted by repair activities. Naval Ships Technical Manuals are the primary source of information for ship's force personnel.

The applicable Chapter for underwater hull preservation is Naval Ships' Technical Manual (NSTM) Chapter 631, Revision 3, Preservation of Ships in Service - General.

Repair Activities

Underwater hull cleaning is accomplished periodically to:

  • Maintain effective leaching rate of anti-fouling coating
  • Improve fuel economy through reduction of hull friction resistance
  • Restore sonar system performance by reducing self noise 
  • Prepare damaged or abraded surfaces for application of underwater curing compounds

Specific instructions on underwater hull cleaning are given in NSTM Chapter 081, Waterborne Underwater Hull Cleaning of Navy Ships.

The Standard Specification for Ship Repair and Alteration Committee (SSRAC) is responsible for providing technically and contractually sound standards for the Navy's ship repair and alteration community.

New Construction Ships

New construction ships are painted in accordance with the applicable sections of the specific Ship Specification for that class of ship.