6 Best Corrosion Protection Options for Cement Plants Burning Alternative Fuels

Alternative Fuel Corrosion Protection: Key Points

• Six options protect cement plants burning alternative fuels: KilnGard® and FlueGard® coatings from Polylloy, refractory upgrades, alloy upgrades, conventional linings, thermal spray and process measures.
• Alternative fuels add variable chlorine, sulfur, fluorine and alkali, so acid gases and salts reach the kiln shell beneath the refractory, and acids condense in ducts, baghouses and stacks.
• Polylloy's KilnGard-600SCW bulletin states that with increased use of alternative fuels, corrosion of the kiln shell under the refractory is more severe; KilnGard-600SCW is rated to 600 °C (1,112 °F) beneath refractory.
• Refractory upgrades, process measures and alloys reduce exposure or raise resistance, but none puts a barrier on existing carbon steel; a practical plan combines a coating with cause-side measures.
• Conventional linings and thermal spray each fit specific zones: linings for acid condensate inside their data sheet rating, thermal spray for oxidation and erosion on hot components, with porosity sealed where condensate forms.
• Longer equipment life can reduce the need for replacement steel and the emissions from producing it; coatings have no direct effect on a plant's process carbon dioxide (CO2).

Six options protect cement plants burning alternative fuels: KilnGard-600SCW beneath kiln refractory with FlueGard grades on ducts and baghouses, refractory upgrades, alloy upgrades, conventional linings, thermal spray and process measures such as sealing false air and sampling deposits. A practical plan combines a coating on exposed steel with measures that cut condensation.

Alternative Fuel Corrosion Protection in Cement Plants Explained

Alternative fuel corrosion protection is the set of coatings, refractory and material choices and operating measures a cement plant uses to keep kiln shells and downstream steel from the extra acid gas, salt and condensate attack that follows co-processing refuse-derived fuel, biomass, tires and other waste-derived fuels.

What Alternative Fuels Change for Plant Equipment

Refuse-derived fuel (RDF), biomass, tires and other waste streams add variable chlorine, sulfur, fluorine and alkali. These form hydrogen chloride (HCl), sulfur trioxide (SO3) and sulfuric acid, hydrogen fluoride (HF) and chloride and sulfate salts that reach the kiln shell through the refractory, as explained in how alternative fuels changed kiln corrosion.

Downstream, higher moisture and acid-forming species can raise the acid dew point, which typically sits between 120 and 160 °C depending on SO3 and moisture (International Cement Review (ICR), May 2026). No single option covers the whole gas path, so the list compares options by zone.

How the 6 Alternative Fuel Corrosion Protection Options Were Selected

The six options were chosen for protecting kiln shells and downstream steel in a cement plant burning alternative fuels.

Selection Criteria

Each option was assessed against five criteria:

• It addresses an alternative-fuel corrosion mechanism: under-refractory attack, acid condensate, chloride deposits or abrasion.
• The zone it fits on the gas path.
• Whether it protects existing steel or only reduces exposure.
• When it can be done: at reline, at an outage or while running.
• Honest limits, including where it is unnecessary.

Order follows fit to that duty. Polylloy's coatings come first because they put a barrier on the steel in both the kiln and downstream zones; the other five follow from kiln-side to downstream to cause-side measures. Cost is project-specific for every option and is discussed as factors only.

Six Alternative Fuel Corrosion Protection Options at a Glance

The table compares the six options by zone, whether they protect steel directly, timing and main limit.

KilnGard and FlueGard Coatings from Polylloy Coatings

Polylloy Coatings formulates coatings that put a barrier on the steel both beneath kiln refractory and in downstream acid gas zones.

Suited To

Kiln shells beneath refractory at reline, and downstream ducts, conditioning towers and baghouses where steel crosses the acid dew point.

What It Is

KilnGard-600SCW is a two-component nano-ceramic composite applied to the kiln shell before the refractory goes back in, for cement and lime kilns, rated to 600 °C (1,112 °F). Its bulletin states that with increased use of alternative fuels, corrosion of the kiln shell under the refractory is more severe.

Final heat cured activation is completed during kiln start-up using process heat, and the coating is typically renewed with refractory replacement.

Downstream, FlueGard-225SQC, a polymeric alloy rated to 225 °C (437 °F), is listed for baghouses, electrostatic precipitators (ESPs) and ducts in cement plants. FlueGard-425S, an inorganic polymeric coating rated to 425 °C (797 °F) with peaks to 500 °C, is listed for conditioning towers and stacks in cement and lime, and FlueGard-455CHT, a ceramic rated to 455 °C (850 °F), suits hot ducts.

Steel stacks take StackGard®-255SQW, rated to 255 °C. The zone-by-zone map is in cement plant corrosion protection by equipment.

Evidence

At a kiln in Mexico, the section from 20 to 26 m, measured at 1 m intervals, lost more than 1.3 mm in 11 months uncoated and showed no measurable loss over a further 12 months coated with KilnGard-600SCW. The study records no fuel mix, so the loss rate is not attributed to alternative fuels; results are project-specific.

FlueGard on coal mill baghouses at three cement plants in Mexico, applied in 2004, 2007 and 2008, was inspected after about 20, 15 and 16 years with no issues observed or excellent condition reported; only the 2008 unit is specifically FlueGard-225SQC.

FlueGard-455CHT on about 75 m² of new duct at a Swiss cement plant showed no visible widespread delamination in inspected areas after about 17 months, with heavy dust limiting the inspection.

Pros and Cons

Pros

• A barrier on the steel in both kiln and downstream zones.
• Fits a reline or outage already planned.
• Partners apply; Polylloy formulates, supplies, specifies, trains and supervises.

Cons

• The kiln coating is only possible with the lining out, and a coating does not replace refractory.
• SSPC-SP10 near-white blast, a Society for Protective Coatings (SSPC) standard, with a profile above 3 mils is needed; heat-cured grades need start-up heat.
• Each grade is bounded by its service limit.

Grade details are on the KilnGard kiln shell protection and FlueGard flue gas coatings pages.

Refractory Upgrades That Reduce Gas and Salt Infiltration to the Kiln Shell

Refractory upgrades work on the path that gas and salts take to the kiln shell.

Suited To

Plants where infiltration through joints, cracks or worn lining is clearly the main path, confirmed by deposit sampling at the shell face during a reline.

What It Is

A refractory upgrade means working with the refractory supplier on brick type and quality, joint and mortar practice, castable zones and anchor layout so less gas and salt reaches the shell. Refractory and anchor redesign is set out among the kiln shell corrosion protection options.

Pros and Cons

Pros

• Addresses a root cause.
• Combines with refractory improvements already under review.

Cons

• Does not protect the steel itself; joints and cracks open over a campaign.
• A more insulating lining lowers shell temperature, which can increase condensation at the steel.

Alloy Upgrades for Ducts, Baghouses and Tanks Downstream of the Kiln

Alloy upgrades replace carbon steel with a material that resists by its own chemistry.

Suited To

New or replacement downstream components and alternative-fuel handling equipment where coating access is poor or conditions exceed every coating limit.

What It Is

An alloy upgrade specifies 316L, duplex or higher alloys instead of carbon steel. According to Polylloy's technical paper on stainless steels, 316L improves localized corrosion resistance compared with 304L but is not immune to chloride pitting and crevice corrosion, which alternative fuels make more likely. The full material set is in alternatives to 316 stainless steel.

Pros and Cons

Pros

• No applied film to maintain.
• Suits small, complex or inaccessible parts.

Cons

• Chloride-bearing deposits and shutdown condensate can still attack stainless.
• Higher alloys need selection for the actual condensate, and replacement means new fabrication.

Protected carbon steel may offer a cost-effective alternative to stainless steel where the coating is suitable for the specified service conditions.

Conventional Linings Such as Novolac Epoxy and Glass-Flake Vinyl Ester Downstream

Conventional linings are the familiar barrier choice for downstream acid zones.

Suited To

Downstream acid condensate zones, such as outlet sections, hoppers and wet stacks, running comfortably inside the product's data sheet rating.

What It Is

Novolac epoxy has a higher crosslink density than standard epoxy and an ambient amine cure; glass-flake vinyl ester is peroxide-cured, with glass flake lengthening the permeation path. Conventional silicone heat-resistant paints belong on dry exteriors, not in acid gas. The chemistries are compared in anti-corrosion coating types.

Pros and Cons

Pros

• Familiar and widely applied.
• Ambient cure fits short outages.

Cons

• Highly crosslinked films can be brittle under thermal shock, and vinyl ester is application-sensitive.
• Not designed for the kiln shell beneath refractory; temperature limits come from each data sheet.

Polylloy's laboratory and field testing comparing FlueGard with conventional high-temperature coatings observed undercutting corrosion and delamination in the conventional coatings; this is Polylloy's own finding, not a verdict on every lining product.

Thermal Spray Coatings for Oxidation and Erosion on Hot Components

Thermal spray deposits a metallic or cermet layer on steel for hot service.

Suited To

Hot components where oxidation, sulfidation or erosion dominates rather than acid condensate.

What It Is

Thermal spray layers include aluminum, nickel-chromium alloys or carbides, deposited by arc spray, flame spray or high-velocity oxy-fuel (HVOF) equipment. Alloy layers resist oxidation and sulfidation, and carbide systems resist erosion. The differences are set out in thermal spray vs polymer-alloy-ceramic coatings.

Pros and Cons

Pros

• Established for hot erosion and oxidation.
• Metallic layers tolerate high temperature.

Cons

• Line-of-sight application limits complex geometry, and specialist equipment is needed.
• Porosity needs sealing where condensate forms, which is where alternative-fuel attack concentrates downstream.

Process Measures That Keep Cement Plant Steel Out of the Condensing Range

Process measures act on the conditions that cause attack rather than on the steel.

Suited To

Every plant raising its alternative fuel rate, as the first step and a companion to any barrier.

What It Is

Measure first: Polylloy's technical paper notes that actual deposits and condensates, minimum wall temperatures, dew point exposure, cleaning practice and shutdown frequency say more than a material name or bulk gas temperature. Record fuel mix alongside deposit chemistry, since RDF and other waste streams vary batch to batch.

Then act on the cause. Seal false air at doors, seals and expansion joints, found by thermography; repair insulation; manage shell temperature in overcooled kiln zones; and clean deposits before long outages where practical. Re-map downstream metal temperatures after a waste heat recovery (WHR) or filter upgrade.

Pros and Cons

Pros

• Treats causes, often with low intrusion.

Cons

• No barrier on the steel, and no protection against shutdown condensate on deposits.
• Dry operation does not prove shutdown exposure is benign.

Symptoms to watch for are listed in acid dew point corrosion warning signs.

Equipment Life, Replacement Steel and Emissions in Alternative Fuel Plants

Equipment protection supports changing industrial processes, including increased alternative fuel use.

What Polylloy Says and Does Not Say

Preserving existing equipment can reduce the need for replacement steel and the emissions associated with its production. Coatings have no direct effect on a plant's process CO2, which comes from raw-material calcination and fuel combustion, and Polylloy does not quantify the replacement-steel effect.

How to Choose Corrosion Protection for a Cement Plant Burning Alternative Fuels

Choosing protection starts with knowing where attack is active and when the next outage falls.

Decision Path by Zone and Timing

Work through the plant in this order:

1. If the alternative fuel substitution rate is rising, survey before the next reline: shell scanner trend, thickness at relines, deposit sampling and downstream metal temperatures.
2. Shell above minimum thickness with a reline planned: protect the shell beneath the new lining.
3. Shell below minimum: replace the section and protect the new steel before relining.
4. Downstream steel crossing the dew point: fix false air and insulation first, then match a coating by service limit, with alloy or thermal spray where access, geometry or erosion call for it.

Dry, ambient, non-condensing steel away from acid fumes and chloride dust does not need a severe-service coating; a conventional system is adequate there.

Cost Factors and Next Step

Pricing depends on the operating environment, selected coating system, equipment condition, project size, and application requirements. Lifecycle evaluation considers preparation, application, maintenance, downtime, and replacement alongside the initial material cost. For a plant manager, a reline or outage already scheduled is the lowest-intrusion window.

To plan the next reline or outage, book a Coating Performance Review with equipment type, coated area, operating conditions (temperature, gas chemistry, abrasion), fuel mix, location and outage timing.

FAQs

What Corrosion Protection Works for Cement Plants Burning Alternative Fuels?

A combination usually works: KilnGard-600SCW on the kiln shell beneath the refractory at reline, FlueGard grades on downstream ducts, conditioning towers and baghouses, and process measures that keep steel above the acid dew point. Refractory upgrades, alloys, conventional linings and thermal spray each fit specific zones. Measure deposits and wall temperatures before choosing.

What Does Alternative Fuel Do to Cement Plant Equipment?

Alternative fuels bring variable chlorine, sulfur, fluorine and alkali into the kiln. These form acid gases and salts that penetrate the refractory and attack the kiln shell, and they can raise moisture and the acid dew point downstream, so ducts, baghouses and stacks condense more acid, especially during shutdowns when deposits absorb moisture.

What Corrosion Risks Come with Refuse-Derived Fuel?

Refuse-derived fuel varies from batch to batch, so chlorine, sulfur and alkali inputs shift with it. The main risks are hydrogen chloride and chloride salts attacking the kiln shell beneath the refractory, acid condensate in downstream ducts and baghouses, and chloride-bearing deposits that hold moisture against steel through outages. Sample deposits to see which species dominate.

Does Extending Equipment Life Reduce Emissions from Replacement Steel?

It can. Preserving existing equipment can reduce the need for replacement steel and the emissions associated with producing it. That is the limit of the claim: coatings have no direct effect on a cement plant's process carbon dioxide, which comes from raw-material calcination and fuel combustion, and Polylloy does not put a figure on the replacement-steel effect.

Is Stainless Steel a Good Answer to Alternative Fuel Corrosion?

Not automatically: 316L improves localized corrosion resistance compared with 304L, but it is not immune to chloride pitting and crevice corrosion, which alternative fuels make more likely. Stainless suits small or inaccessible parts. For large accessible steel, protected carbon steel may offer a cost-effective alternative where the coating suits the service conditions.

Can Thermal Spray Protect Cement Plant Ducts Against Alternative Fuel Corrosion?

Thermal spray suits hot components where oxidation, sulfidation or erosion dominates. Where acid condenses, its porosity needs sealing, and line-of-sight application limits complex geometry. Downstream ducts and baghouses that cross the acid dew point are usually better matched to a coating rated for acid condensate at their service temperature.

When Can KilnGard-600SCW Be Applied on a Kiln Burning Alternative Fuels?

At a planned reline. With the refractory removed, a partner blasts the shell to near-white and applies KilnGard-600SCW under Polylloy supervision, then the new lining goes in. It is rated to 600 °C for cement and lime kiln shells, and final heat cured activation is completed during kiln start-up using process heat.