Coatings Comparison
Insulating Ceramic Coating vs Metal Jacketing for CUI and Hot Surfaces
Metal jacketing keeps weather off insulation, but CUI starts where water slips past its seams and sits against hidden steel. An insulating ceramic coating bonds directly to the steel, leaving no annulus to hold water and no jacket to remove for inspection.
Metal jacketing, usually aluminum or stainless sheet, is the outer weather barrier on a conventional insulation system. It does its job well while every lap, seam, band and penetration stays sealed. Corrosion under insulation (CUI) begins when one of those details opens up: rain, washdown water or condensation gets behind the jacket, collects in the insulation and the annulus around the pipe, and stays in contact with the steel where nobody can see it.
An insulating ceramic coating takes a different approach. NanoTech Insulator is a water-based coating built on the patented Insulative Ceramic Particle, sprayed directly onto primed steel and bonded to it. There is no jacket, no seam and no gap between the insulating layer and the substrate, so there is no space for water to collect, and the coated surface can be looked at on a routine walk-down.
Jacketing is still the better fit in some places: service temperatures above the coating's published range, systems where conserving heat is the main objective and thickness pays for itself, and locations where the insulation needs a hard shell against mechanical abuse. The sections below cover where each approach earns its place.
Quick verdict
Best for
Insulating ceramic coating (NanoTech Insulator)
- CUI-exposed piping, tanks and vessels in coastal, humid, washdown or cyclic-temperature service
- Hot surfaces near operators and maintenance crews where the goal is a lower touch temperature
- Valves, flanges, exchanger heads and irregular shapes where cut-and-fit insulation leaves gaps
- Asset-integrity programs that want the substrate visible for inspection
- Work that cannot wait for a turnaround, within the coating's active-equipment application limits
Best for
Metal jacketing over insulation
- Service temperatures above the coating's published system range
- Large high-temperature systems where heat conservation is the objective and added thickness pays back
- Locations that need a hard shell against foot traffic, impact or abrasion
- Specifications that call for a listed insulation system under jacketing
Insulating ceramic coating vs metal jacketing (side by side)
| Attribute | Insulating Ceramic Coating (NanoTech Insulator) | Metal Jacketing over Insulation |
|---|---|---|
| What it is | A water-based insulating coating sprayed and bonded directly to the substrate | An aluminum or stainless sheet weather barrier wrapped over mineral wool, calcium silicate, cellular glass or similar insulation |
| Where water can enter | No jacket seams, laps or bands; the film is continuous over the surface | Laps, seams, bands, penetrations, supports and terminations, plus any damage to the sheet |
| Annulus against the steel | None: the coating is bonded to the primed substrate | Present: water that gets in can sit in the insulation and against the pipe wall |
| Inspection | Visual, on a routine walk-down | Jacketing and insulation are removed, or NDE is used, to see the steel |
| Touch temperature | 41 mil DFT met the 58°C, 5-second contact criterion at a 275°F (135°C) substrate in NACE TM21423-2023 testing | Depends on insulation type and thickness; the jacket surface is what personnel touch |
| Corrosion and condensation testing | ISO 9227 neutral salt spray and ISO 6270-1 condensation: visual Rating 0 per ISO 4628, no blistering, rusting, cracking or flaking | Corrosion protection depends on the coating under the insulation and on keeping the jacket sealed |
| Geometry | Conforms to valves, flanges, nozzles and curved shells; good vertical hang | Cut-and-fit around fittings, with more seams at each irregular shape |
| Build | Up to 40 mils DFT per pass; recommended 40 to 200 mils DFT depending on the job (TDS) | Inches of insulation plus the jacket |
| Trades | One applicator crew; NanoTech Zinc Primer on carbon steel, self-priming on non-ferrous metals | Insulation and sheet-metal work, usually with scaffolding |
| Mechanical protection | A coating film, not a hard shell | A metal shell that takes foot traffic and impact |
Inspection: AMPP SP0198 and API RP 583 both address managing CUI under insulation systems.
Touch temperature: Coating result per the NanoTech Insulator Technical Data Sheet (rev. 10/21/2026). ASTM C1057 is the standard practice for determining contact temperature.
Corrosion and condensation testing: The salt-spray result is a visual coating-condition assessment and is not presented as ISO 12944-6 qualification (NanoTech Insulator TDS).
Which approach fits your use case?
Process piping and vessels in coastal or humid service, in the CUI temperature range
Pick: Insulating Ceramic Coating (NanoTech Insulator)This is where jacket seams take on water and where CUI is most expensive to find. A bonded coating leaves no annulus for water to sit in, and the steel stays visible between inspections.
Hot surfaces near walkways and work areas
Pick: Insulating Ceramic Coating (NanoTech Insulator)NanoTech Insulator is built for lowering touch temperature on hot equipment. In NACE TM21423-2023 testing, a 41 mil film met the 58°C, 5-second contact criterion on a 275°F (135°C) substrate.
Valves, flanges, exchanger heads and skid equipment
Pick: Insulating Ceramic Coating (NanoTech Insulator)Each fitting is a cut-and-fit detail and another set of seams under a jacket. A sprayed coating follows the shape and can be applied in the fabrication shop on modular equipment.
High-temperature steam header where conserving heat is the project
Pick: Metal Jacketing over InsulationWhen the engineering objective is minimizing heat loss and thickness is acceptable, inches of insulation under well-maintained jacketing are the practical choice. Keep the jacket sealed and on an inspection schedule.
Pipe racks and platforms with foot traffic or impact risk
Pick: Metal Jacketing over InsulationA metal jacket is a hard shell. Where the insulation has to stand up to people walking on it or to dropped tools, jacketing carries a load a coating film is not designed for.
Mixed temperature systems
Tie / dependsMany plants use both: jacketed insulation on the hottest runs and the coating on CUI-prone sections, fittings and personnel-contact areas inside its range.
Where metal jacketing is the better pick
Jacketed insulation is the industry standard for good reasons. It is widely specified, contractors know it, insulation thickness is easy to scale for heat conservation, and the metal shell protects the insulation from weather and mechanical damage. On large, high-temperature systems where the priority is keeping heat in the line, it is often the right answer.
The coating has limits worth stating plainly. NanoTech's published personnel-protection systems run to substrates up to 350°F with two coats (NanoTech Insulator Quick Specification, rev. 11/02/2026); above that, specify conventional high-temperature insulation. A coating film is also not a hard shell, so areas exposed to foot traffic or impact still call for jacketing. And where a project specification calls for a listed insulation system, that requirement governs.
How the two approaches work
Jacketed insulation slows heat flow with thickness: inches of fibrous, granular or cellular material, covered by a metal sheet that keeps weather out. The system depends on the jacket staying sealed. Laps, seams, bands, supports and penetrations are the details that open up over time, and once water is behind the jacket it can sit in the insulation and in the annulus against the pipe, out of sight. AMPP SP0198 and API RP 583 exist largely to manage that risk through design, coatings under the insulation, and inspection planning.
NanoTech Insulator works as a bonded film. The Insulative Ceramic Particle gives the coating low thermal conductivity and high emissivity, so it slows heat transfer through the film and gives off heat at the surface. Because it is sprayed onto a primed substrate and bonded to it, there is no annulus. In NACE TM21423-2023 testing, a 41 mil DFT film met the 58°C, 5-second contact criterion at a 275°F (135°C) substrate. Corrosion and condensation exposure under ISO 9227 and ISO 6270-1 produced a visual Rating 0 per ISO 4628, with no blistering, rusting, cracking or flaking (Technical Data Sheet, rev. 10/21/2026).
Application is one trade. Carbon steel is prepared and primed with NanoTech Zinc Primer; non-ferrous metals take the coating directly. The coating builds up to 40 mils DFT per pass, and the number of passes depends on operating temperature and the degree of personnel protection or condensation control required, so the system is specified per project with NanoTech Technical Service.
Related pages
Insulative Coating System
The three-layer system: NanoTech Zinc Primer, NanoTech Insulator and NanoTech Insulator TopCoat, with technical documents.
CUI prevention coating
How a bonded insulative film changes corrosion-under-insulation risk on piping, tanks and vessels.
NanoTech Insulator vs Mineral Wool & Jacketing
A material-level comparison against mineral wool, including heat conservation at higher temperatures.
Insulating coating vs metal jacketing: what actually decides it
Our blog walk-through of the decision factors, from seams and inspection to service temperature.
Frequently asked questions
What is the difference between an insulating ceramic coating and metal jacketing?
Where does corrosion under insulation start on jacketed systems?
How does a bonded insulating coating change CUI inspection?
What touch temperature does NanoTech Insulator achieve?
When is metal jacketing still the better choice?
Can the coating be applied without shutting the equipment down?
Compare your line list against both options
Send us service temperatures, environment and access constraints. The NanoTech technical team will mark where a bonded insulating coating fits, and where jacketed insulation is still the better specification.