Exterior exhaust piping, boilers, economizers, and other high-temperature machinery and piping all require a corrosion-resistant barrier to protect the surface from the corrosion-prone or weather-exposed environments in which the equipment operates. The Navy uses special heat-resistant coatings on surfaces with operating temperatures ranging from 400°F to 1200°F. These paints contain aluminum pigment in a silicone or modified silicone resin. The federal specification which governs these high-heat aluminum coatings is TT-P-28. This specification includes two types of heat-resistant coatings: Type I is a liquid form of paint that can withstand temperatures up to 650°C (1200°F), and Type II is a powder coating that can withstand temperatures up to 372°C (700°F). There are currently no qualified Type II coatings.
The degree of surface cleanliness required is determined by the structure being coated. For example, NAVSEA Standard Item 009-32 requires an SSPC SP-11 Power Tool Cleaning to Bare Metal surface preparation for boilers and economizers. For high-temperature piping and machinery that operates at temperatures ranging from 400°F to 1200°F, surface preparation cleanliness must meet SSPC-SP 10/NACE No. 2 Near-White Metal Blast requirements.
Per Naval Ships Technical Manual Chapter (NSTM) Chapter 631, heat-resistant paint is highly flammable during application and shall not be applied to surfaces whose temperature at the time of application exceeds 29°C (85°F). All safety precautions must be followed during preservation efforts, particularly in enclosed spaces due to the release of carbon monoxide and other hazardous vapors during curing.
“Painting Application Procedures” in Naval Ships Technical Manual: Chapter 631, Preservation of Ships in Service – General, Rev 3, sec 7, pp. 631-7-23 – 631-7-24.