# Thermal Spray vs Polymer-Alloy-Ceramic Coatings: 6 Differences for Flue Gas Steel A polymer-alloy-ceramic coating is Polylloy Coatings' family of hybrid films bonded to blast-cleaned steel, with ceramic grades such as FlueGard-455CHT rated to 455 °C (850 °F); a thermal spray coating is a sprayed metallic or cermet deposit. They differ in six ways: layer, condensate barrier, temperature basis, abrasion, application access, and cure and repair. **Category:** Listicles **Written by:** Edita Rojasova **Last updated:** Oct 27, 2026 **Source:** https://signals.polylloycoatings.com/listicles/thermal-spray-vs-ceramic-coatings --- ## Thermal Spray vs Ceramic Coatings: Key Points - A polymer-alloy-ceramic coating is Polylloy Coatings' family of hybrid films bonded to blast-cleaned steel; its ceramic grades are FlueGard®-455CHT (ceramic, 455 °C (850 °F)), WearGard®-625S (nano-ceramic, 625 °C) and KilnGard®-600SCW (nano-ceramic, beneath refractory). - A thermal spray coating is a metallic or cermet layer, such as aluminum, nickel-chromium alloy or carbide, deposited by arc spray, flame spray or high-velocity oxy-fuel (HVOF) equipment and mechanically bonded to a blasted surface. - The sharpest difference for flue gas steel is the condensate barrier: thermal spray porosity is often sealed where acid condensate forms, while FlueGard-455CHT lists good resistance to acidic and alkaline condensates. - Thermal spray temperature capability is set by its alloy or carbide system, and carbide systems resist erosion strongly; Polylloy's listed limits stop at 625 °C, so hotter duty points to thermal spray, refractory or alloy. - Polylloy ceramic grades need an SSPC-SP10 near-white blast, are inspected and repaired before final cure, and complete final heat cured activation during start-up using process heat. - Certified partners apply Polylloy coatings under Polylloy specification and supervision. A polymer-alloy-ceramic coating is Polylloy Coatings' family of hybrid films bonded to blast-cleaned steel, with ceramic grades such as FlueGard-455CHT rated to 455 °C (850 °F); a thermal spray coating is a sprayed metallic or cermet deposit. They differ in six ways: layer, condensate barrier, temperature basis, abrasion, application access, and cure and repair. ## Thermal Spray Coatings and Polymer-Alloy-Ceramic Coatings Defined Both technologies protect hot steel, but they are built in different ways. ### What a Polymer-Alloy-Ceramic Coating Is A polymer-alloy-ceramic coating is Polylloy Coatings' family name for hybrid films bonded to blast-cleaned steel. In Polylloy's description, the ceramic phase forms a dense barrier while the alloy and polymer phases give adhesion and flexibility compatible with the thermal expansion of steel. Only some grades are ceramic. FlueGard-455CHT is a ceramic coating, and WearGard-625S and KilnGard-600SCW are nano-ceramic; FlueGard-225SQC is a polymeric alloy and FlueGard-425S an inorganic polymeric coating, so neither is a ceramic coating. The chemistry differences are explained in [industrial ceramic coatings for steel](https://signals.polylloycoatings.com/articles/industrial-ceramic-coatings-steel). ### What a Thermal Spray Coating Is A thermal spray coating is a metallic or cermet layer, such as aluminum, nickel-chromium alloys or carbides, built up from molten or semi-molten particles. It is deposited by arc spray, flame spray or HVOF equipment and mechanically bonded to a blasted surface. Alloy layers resist oxidation and sulfidation, and carbide systems resist erosion. This page describes thermal spray generically; ratings belong to each system's own data sheet. ## How the Six Thermal Spray vs Ceramic Coating Differences Were Chosen Each difference in this list meets three criteria: - It changes a specification decision for flue gas or hot abrasive steel. - It rests on Polylloy's published bulletin data on one side and generic, qualitative thermal spray practice on the other. - It can be checked on a data sheet or method statement. The order follows the specification path: what the layer is, how it handles condensate, temperature, abrasion, how it is applied, and how it is cured, inspected and repaired. ## Thermal Spray vs Polymer-Alloy-Ceramic Coatings at a Glance The table summarizes the six differences in the order they are described. Thermal spray cells stay generic because no maker's figures are cited. | Difference | Thermal spray coating | Polylloy ceramic grades | What to ask for | | --- | --- | --- | --- | | Layer type | Metallic or cermet deposit | Bonded hybrid ceramic or nano-ceramic film | Layer composition and bond type | | Condensate barrier | Porosity often sealed | 455CHT lists acidic and alkaline condensate resistance | Behavior at a defect | | Temperature basis | Per alloy or carbide system | 455 °C (850 °F) for 455CHT, 625 °C for 625S | Continuous and peak limits | | Abrasion | Carbides resist erosion | Taber 20 mg (455CHT), below 30 mg (625S) | Same test method | | Application access | Line-of-sight, specialized equipment | 625S by spray, roller or brush | Access to internal geometry | | Cure and repair | Sealer per maker's procedure | Repair before final cure, start-up activation | Repair method statement | ## Layer Type: Sprayed Metal or Cermet Deposit vs Bonded Hybrid Ceramic Film The first difference is what the protective layer is made of and how it attaches. ### Thermal Spray Coating A thermal spray coating is a metallic or cermet deposit built from sprayed particles and mechanically bonded to the blast profile. Its chemistry is set by the wire or powder chosen. ### Polylloy Ceramic Grades FlueGard-455CHT is a two-component, water-based ceramic corrosion and abrasion coating, and WearGard-625S is a two-component nano-ceramic abrasion-resistant material. The KilnGard-600SCW and WearGard-625S bulletins attribute chemical and salt corrosion resistance to a "tough impervious ceramic nature and a strong bond to the metal substrate." ### What It Means for Flue Gas Steel Specify by grade code and data sheet, not by the words "ceramic" or "thermal spray." Ask what the layer is made of and how it attaches to the steel. ## Acid Condensate Barrier: Porosity and Sealing vs a Continuous Bonded Film The second difference matters most where flue gas steel cools through the acid dew point. ### Thermal Spray Coating Thermal spray layers carry porosity that is often sealed, especially where condensate can form during cool-down. Ask how the sealed system is specified for acid service. ### Polylloy Ceramic Grades FlueGard-455CHT lists good resistance to acidic and alkaline condensates. KilnGard-600SCW and WearGard-625S report one-week immersion weight gain below 0.5% in 36% sulfuric acid and below 1.0% in 50% sodium hydroxide; these are laboratory property data, not an immersion service rating. None of the three is an immersion grade. Flue gas steel cools through the acid dew point, typically 120 to 160 °C in cement plant gas (International Cement Review (ICR), May 2026), at shutdowns. The ICR article stresses resistance to undercut corrosion where condensate meets a defect. ### What It Means for Flue Gas Steel Ask any system how it behaves when acid condenses at a defect. For wet, acid-condensing service within 225 °C, Polylloy points to FlueGard-225SQC, a polymeric alloy that is immersion-rated, rather than a ceramic grade. ## Temperature Basis: Alloy or Carbide System vs Listed Service Limits The third difference is how the temperature ceiling is defined. ### Thermal Spray Coating Thermal spray offers high temperature capability, set by the alloy or carbide system chosen. The maker's data sheet gives the figure for each system. ### Polylloy Ceramic Grades FlueGard-455CHT is rated to 455 °C (850 °F), WearGard-625S to 625 °C (1,157 °F), and KilnGard-600SCW to 600 °C beneath refractory only. Service above 625 °C is outside Polylloy's listed range. On about 75 m² of new duct at a Swiss cement plant, running 220 to 240 °C continuously with about 50 shutdowns a year, inspected areas of FlueGard-455CHT showed no visible widespread delamination at about 17 months. Heavy dust limited the inspection; the case is covered in [hot flue gas duct protection through cycling](https://signals.polylloycoatings.com/use-cases/hot-flue-gas-duct-protection). ### What It Means for Flue Gas Steel Give both the continuous temperature and the maximum excursion, and never extrapolate a grade beyond its listed limit or applications. The wider field is compared in [high temperature coatings above 400 °C](https://signals.polylloycoatings.com/listicles/high-temperature-coatings-400c). ## Abrasion and Erosion: Carbide Deposits vs Published Taber Data The fourth difference is how abrasion resistance is demonstrated. ### Thermal Spray Coating Carbide thermal spray systems are chosen for strong erosion resistance on boiler tubes, hot components and accessible duct surfaces. ### Polylloy Ceramic Grades FlueGard-455CHT lists Taber abrasion of 20 mg (CS-17, 1 kg, 1,000 cycles) and Shore D hardness above 80. WearGard-625S lists Taber below 30 mg, Shore D above 95 and impact above 40 in-lb, with bulletin applications in cement and lime ducts, coal power and waste incineration fans and ducts, and smelter ducts, filters and stacks. Polylloy also places WearGard-625S on cyclones, chutes, hoppers, transfer points and separators, as set out in [wear resistant coatings for cyclones, chutes and hoppers](https://signals.polylloycoatings.com/use-cases/abrasion-wear-resistant-coatings). ### What It Means for Flue Gas Steel No published head-to-head abrasion test compares thermal spray and Polylloy grades, so compare published data on the same test method and do not assume either wins. Heavy lump impact may still call for liner plate with either route. ## Application Equipment and Access: Line-of-Sight Spraying vs Spray, Roller or Brush The fifth difference is how the coating reaches the steel. ### Thermal Spray Coating Thermal spray needs specialized arc, flame or HVOF equipment, line-of-sight access and critical surface preparation. ### Polylloy Ceramic Grades WearGard-625S goes on by air spray, roller or brush on clean, sandblasted, dry steel. FlueGard-455CHT is applied in two coats to 16 to 20 mils (400 to 500 µm) total and thinned with distilled water. Every grade needs SSPC-SP10 / NACE No. 2 near-white metal with a profile above 3 mils (75 µm). Certified partners apply the coatings; Polylloy formulates, supplies, specifies, trains and supervises. The outage sequence is set out in [coating outage planning steps](https://signals.polylloycoatings.com/articles/coating-outage-planning-steps). ### What It Means for Flue Gas Steel Check access around stiffeners, corners and internal geometry, and confirm who will apply and inspect, before choosing the technology. ## Cure, Inspection and Repair Before the Equipment Returns to Service The sixth difference is what happens between application and start-up. ### Thermal Spray Coating Any sealer and its curing follow the maker's procedure. Inspection and repair follow the applicator's method statement. ### Polylloy Ceramic Grades The WearGard-625S bulletin states the film can be inspected for thickness and integrity and any defect recoated before final cure, and lists easy inspection and maintenance as a highlight. Final heat cured activation is completed during start-up using process heat. ### What It Means for Flue Gas Steel Confirm that start-up heat reaches every coated area. A site that cannot blast to standard or reach activation is not a fit for Polylloy grades. ## Where Thermal Spray is the Better Fit for Hot Steel Thermal spray is the stronger candidate in three situations: - Service above 625 °C, outside Polylloy's listed range. - Boiler tubes and hot components where oxidation, sulfidation or erosion dominate and condensate does not form. - Owner standards that call for a specific thermal spray system. Polylloy ceramic grades are not immersion grades and are heat-cured. Mild, dry, cool steel needs only a conventional coating. ## Choosing Between Thermal Spray and a Polymer-Alloy-Ceramic Coating Choosing between thermal spray and a polymer-alloy-ceramic coating starts with temperature, condensate and abrasion together. ### Decision Rules Match the duty to the route: - Heat plus abrasion plus acidic or alkaline condensate up to 455 °C (850 °F): evaluate FlueGard-455CHT. - Hot abrasive gas streams to 625 °C: WearGard-625S. - Steel beneath refractory in kilns, incinerator furnaces and smelter ducts or stacks, to 600 °C: KilnGard-600SCW. - Above 625 °C, or erosion-dominated hot components with no condensate: thermal spray, refractory or alloy. - Wet, acid-condensing service within 225 °C: FlueGard-225SQC. Ask both suppliers for the same data on the same methods: temperature basis, condensate behavior, abrasion test, adhesion test, application method and repair procedure. The full grade ladder is in [coating grades by temperature and gas chemistry](https://signals.polylloycoatings.com/listicles/coating-grades-temperature-chemistry). ### Cost and Next Step Pricing depends on the operating environment, selected coating system, equipment condition, project size, and application requirements. The grade family is described on the [FlueGard high temperature coatings](https://www.polylloycoatings.com/fluegard) page. To book a Coating Performance Review, [request a coating evaluation](https://www.polylloycoatings.com/contact) and share equipment type, coated area, operating conditions (continuous and peak temperature, gas chemistry, abrasion), location and outage timing. ### FAQs **What is a Polymer Alloy Ceramic Coating?** A polymer-alloy-ceramic coating is Polylloy Coatings' family of hybrid protective films bonded to blast-cleaned steel for heat, abrasion and chemical resistance. Only some grades are ceramic: FlueGard-455CHT is a ceramic coating to 455 °C (850 °F), and WearGard-625S and KilnGard-600SCW are nano-ceramic. FlueGard-225SQC is a polymeric alloy, so specify by grade code. **What is the Difference Between Thermal Spray and Ceramic Coating?** A thermal spray coating is a metallic or cermet deposit sprayed from molten or semi-molten particles with arc, flame or HVOF equipment. A ceramic coating such as FlueGard-455CHT is a two-component film applied as a liquid and bonded to blasted steel. The practical differences are condensate behavior, temperature basis, abrasion data, access, and cure and repair. **Is Thermal Spray Suitable for Acid Flue Gas Condensate?** It can be, with the right system and sealer. Thermal spray layers have porosity that is often sealed where acid condensate can form during cool-down, so ask the supplier how the sealed system behaves at a defect. Polylloy's FlueGard-455CHT lists good resistance to acidic and alkaline condensates to 455 °C (850 °F). **What Ceramic Coating Can Protect Steel at 455 °C (850 °F)?** FlueGard-455CHT is a two-component ceramic corrosion and abrasion coating rated to 455 °C (850 °F). Its data sheet lists Taber abrasion of 20 mg, Shore D hardness above 80 and Elcometer adhesion above 1,000 psi (7 MPa) on sandblasted carbon steel, with good resistance to acidic and alkaline condensates. It requires an SSPC-SP10 near-white blast. **When is Thermal Spray a Better Choice Than a Polylloy Ceramic Coating?** Thermal spray is the stronger candidate above 625 °C, which is outside Polylloy's listed range, and on boiler tubes and hot components where oxidation, sulfidation or erosion dominate and no condensate forms. It also fits where the owner's standard calls for a specific thermal spray system. Compare both on the same data and conditions. **Which is More Abrasion Resistant, Thermal Spray or WearGard-625S?** No head-to-head test is published, so neither should be claimed as more resistant. Carbide thermal spray systems are chosen for strong erosion resistance, while WearGard-625S lists Taber abrasion below 30 mg and Shore D above 95 to 625 °C. Ask for abrasion data on the same test method before deciding. **Do Polylloy Ceramic Coatings Need Heat to Cure?** Yes: FlueGard-455CHT, WearGard-625S and KilnGard-600SCW are heat-cured, and final heat cured activation is completed during start-up using process heat. Before that, the film can be inspected for thickness and integrity and defects recoated. Where start-up heat cannot reach a coated area, a heat-cured grade is not a fit there, so review it with Polylloy's technical team first.