MACHINERY AND OTHER WET SPACES
Coating systems discussed in this section are designed for application in severe environments, including mixing rooms, uptake spaces, machinery spaces, bilges, and other wet spaces. These environments are frequently wet due to condensation, weather exposure, and bilge fluids. Although these compartments all receive similar coating systems to protect against their severe environmental conditions, these conditions can be quite different.
Mixing rooms and uptake spaces are connected directly to the outside atmosphere by vents or louvers and need adequate protection from the harsh salt air environment. Machinery spaces and bilges are often chronically wet and can be hard to reach and clean. This presents an elevated preservation problem that can generally only be addressed during periodic maintenance availabilities. Wet spaces are interior compartments of U.S. Navy ships that are frequently wet or exposed to heavy condensation. These areas include washrooms, water closets, shower stalls, sculleries, storerooms and galleys.
These areas are first coated with an anti-corrosive primer and then top coated with an epoxy-polyamide based paint, an epoxy system, or an interior enamel, depending upon their service location.
Anti-corrosive primer is first applied to the substrate in these areas. This primer is a single coat of MIL-PRF-23236, Type VII, Class 5, 5/18, 15B, 17, or 17/18. Alternatively, wet spaces may be primed with a single coat of MIL-PRF-32171, Type III, Class 1 or 2.
The topcoat consists of an epoxy-polyamide based paint, an epoxy system, or an interior enamel. Wet spaces may be topcoated with MIL-PRF-24635, Type V or VI, or MIL-PRF-32171, Type III, Class 1 or 2. The color of this topcoat is determined by the Type Commander (TYCOM) or the ship’s Commanding Officer. For machinery spaces, NSI 009-32 requires the use of two coats of F-124, MIL-DTL-24607 in areas above the bilge. Within the bilge area itself, MIL-PRF-23236, Type VII, Class 5, 15B, or 17 may be used. Mixing rooms and uptake spaces are required to be coated with haze gray or light gray, MIL-PRF-23236, Type VII, Class 5 on decks, bulkheads, and overheads.
To ensure coating adhesion, special attention should be paid to the surface preparation in accordance with NSI 009-32. For machinery spaces and bilges, SSPC-SP 11, Bare Metal Power Tool Cleaning; NACE/SSPC-SP WJ-2, Very Thorough Waterjetting; or SSPC-SP 10/NACE No. 2, Near-White Blast Cleaning are required for surface preparation. Mixing rooms and uptake spaces are required to be abrasive blasted in accordance with SSPC-SP 10/NACE No. 2. For wet spaces, power tool cleaning in accordance with SSPC-SP 11 is required for decks, while SSPC-SP 3, Power Tool Cleaning is sufficient for bulkheads and overheads.
NSI 009-32 is the governing document for preservation requirements. Permitted coatings are specified in Table 3. All interior compartment coating system preservation efforts must be accomplished in accordance with NSI 009-32.
Ship’s force personnel are responsible for wet space compartment coating system integrity until repair activity maintenance is scheduled. Naval Ships Technical Manual: Chapter 631 (NSTM 631), Preservation of Ships in Service – General provides requirements, instructions, and guidance for surface preparation and coating application.
New construction ships are painted in accordance with the ship build specification for that class of ship.