Refinery and Petrochemical Flue Gas Corrosion Protection

Refinery Flue Gas Protection: Key Points

• Refinery flue gas carries sulfur oxides, hydrogen chloride and dust; steel below the acid dew point collects acid condensate, so protection is chosen by steel temperature first, then chemistry and abrasion.
• Polylloy bulletins list refinery service for four grades: FlueGard®-225SQC (225 °C), StackGard®-255SQW (255 °C), FlueGard-425S (425 °C with peaks to 500 °C) and CorrosionGard®-160S (160 °C) for structures and equipment.
• A refinery high temperature coating for internal flue gas is a different duty from an exterior heat-resistant or corrosion under insulation coating; ask for acid gas and condensate data, not only a heat rating.
• Continuously wetted, high-chloride scrubber zones usually stay with established linings or alloys; Polylloy grades fit the gas side, and immersion fit is confirmed per project.
• On an Exxon Canada stack in 2026, KilnGard®-600SCW was shop-applied beneath the refractory: an application-stage reference with no in-service claim.
• Polylloy formulates, supplies, specifies, trains and supervises; certified partners apply. Protected carbon steel may offer a cost-effective alternative to stainless steel where the coating is suitable for the specified service conditions.

A refinery high temperature coating for flue gas service is chosen by steel temperature, then chemistry and abrasion. Polylloy bulletins list refinery ducts, scrubbers and chimneys for FlueGard-225SQC (225 °C), StackGard-255SQW (255 °C) and FlueGard-425S (425 °C, peaks 500 °C), with CorrosionGard-160S for structures; wetted scrubber zones need project confirmation.

Refinery and petrochemical flue gas corrosion protection is the selection of internal coatings, linings or alloys for the steel ducts, scrubbers, fans and stacks that carry combustion gas from heaters, boilers and incinerators. The aim is steel that resists acid condensate, sulfur oxides, hydrogen chloride (HCl), dust and thermal cycling at its operating temperature.

Refinery and Petrochemical Flue Gas Challenges and How Polylloy Grades Address Them

Refinery and petrochemical flue gas corrosion protection matches each piece of gas-path steel to a grade by temperature, chemistry and abrasion, as the table shows.

Where Flue Gas Corrodes Steel in Refineries and Petrochemical Plants

Flue gas corrodes refinery steel wherever it meets a surface cool enough to condense acid.

Sulfur Oxides, HCl and the Acid Dew Point

Polylloy's FlueGard and StackGard bulletins state that flue gases in oil refineries, power plants, cement plants, smelters and waste incineration contain sulfur trioxide (SO3), sulfur dioxide (SO2), HCl, nitrogen oxides (NOx) and dust, and are extremely corrosive and abrasive.

SO3 combines with water vapor to form sulfuric acid, and the acid dew point rises with SO3 concentration and moisture. Polylloy's May 2026 International Cement Review article adds that false air at seals and joints cools steel locally, pushing it below that dew point.

The Refinery Flue Gas Path, Zone by Zone

Fired heaters and boilers feed flue gas ducts, gas scrubbers (including FGD), ID fans and stacks. Stack tops, outlet ducts, flanges, stiffeners and idle bypasses run coolest and condense acid first, and low load and start-stop operation enlarge the cold area.

Petrochemical plants with heaters, boilers or thermal oxidizers have the same gas-side zones. Tanks, vessels and process equipment are a separate chemical-service selection and are not covered here.

Matching Polylloy Grades to Refinery Flue Gas Equipment by Bulletin Listing

Polylloy grades are matched to refinery equipment by what each bulletin lists, then by temperature. Full test data per grade are compared in coating grades by temperature and chemistry.

Grades Listed for Refinery Service

Four bulletins name oil refineries among their applications:

• FlueGard-225SQC: two-component polymeric alloy to 225 °C (437 °F), listed for FGD scrubbers, ducts and chimneys in oil refineries; resistant to SO3, SO2, HCl, carbon dioxide, hydrogen fluoride (HF) and NOx, and immersion-rated.
• StackGard-255SQW: to 255 °C (491 °F), listed for the inside surfaces of steel chimneys connected to gas scrubbers, ducts and fans in refineries.
• FlueGard-425S: single-component inorganic polymeric coating from ambient to 425 °C (797 °F) with peaks to 500 °C, listed for gas scrubbers, ducts and chimneys in refineries; not immersion-rated.
• CorrosionGard-160S: ambient-cure coating to 160 °C (320 °F), listed for steel structures and equipment in refineries.

Listings and data are on the FlueGard flue gas coatings and StackGard stack coating pages.

Hotter, Dustier Ducts: FlueGard-455CHT

FlueGard-455CHT is a two-component ceramic corrosion and abrasion coating to 455 °C (850 °F), with a Taber abrasion loss of 20 mg and good resistance to acidic and alkaline condensates. Its data sheet lists no industry, so refinery use follows a technical review by Polylloy's team; the cycling duty it addresses is covered under hot flue gas duct protection.

Steel Beneath Refractory

On refractory-lined stacks the steel is coated before the lining goes in. In 2026, KilnGard-600SCW (600 °C) was shop-applied to 18 prefabricated sections of an Exxon Canada stack, an application-stage reference with no in-service claim; the sequence is set out in coating a refractory-lined stack.

A Refinery High Temperature Coating for Flue Gas is Not an Exterior Heat or CUI Coating

In refineries, "high temperature coating" usually means something different from an internal flue gas coating.

Two Different Duties

The term often refers to exterior heat-resistant or corrosion under insulation (CUI) coatings on hot piping and vessels. Those protect the outside of the steel from heat, moisture and atmosphere; an exterior heat rating does not establish resistance to internal acid gas, as the hot duct article above explains.

Polylloy grades are formulated for the internal flue gas path. The FlueGard-425S bulletin also notes resistance to chemical and salt corrosion in external high-temperature applications in industrial and marine environments, but insulated-piping CUI is not a listed application, so that duty goes to Polylloy's technical team.

When a Conventional Coating is Enough

Mild service is not a fit. Dry, warm steel well above the dew point, with no acid gas or abrasion, is usually served by a conventional coating.

Refinery Stack and Scrubber Corrosion Protection

Refinery stacks and scrubbers are split first by whether the steel stays dry or runs wet.

Refinery Stacks: Dry or Wet First

Dry or intermittently condensing steel stacks to 255 °C suit StackGard-255SQW, or FlueGard-225SQC to 225 °C. Hotter stacks point to FlueGard-425S, whose bulletin lists chimneys in refineries. Saturated wet stacks after wet scrubbing need an immersion-rated system or established wet-stack linings.

Coatings can go inside an existing stack, on replacement sections on the ground, or on new sections before assembly. Options and suppliers for each route are compared in stack and chimney lining suppliers.

Refinery Scrubbers: Gas Side vs Wetted Zones

FlueGard-225SQC is listed for FGD scrubbers in refineries and is immersion-rated, but continuously wetted, high-chloride slurry zones traditionally use rubber, glass-flake vinyl ester or nickel alloy, and any coating there needs written confirmation. FlueGard-425S and StackGard-255SQW are not immersion grades. The zone-by-zone picture is in flue gas desulfurization corrosion.

Protected Carbon Steel vs 316 Stainless Steel in Refinery Flue Gas Equipment

Protected carbon steel and 316 stainless should be compared at the design stage, before the material schedule is fixed.

The Design-Stage Comparison

316 stainless is Polylloy's primary benchmark. According to Polylloy's technical document, its molybdenum improves localized corrosion resistance compared with 304L but gives no immunity to chloride pitting, crevice corrosion or stress corrosion cracking in acidic chloride condensate.

Protected carbon steel may offer a cost-effective alternative to stainless steel where the coating is suitable for the specified service conditions. Compare both on the same equipment, conditions, scope and evaluation period; the full argument is in carbon steel vs stainless steel.

How EPC Engineers Specify Refinery Flue Gas Protection

Engineering, procurement and construction (EPC) engineers specify from process inputs, then check the site against a qualification gate.

Specification Inputs and Qualification Gate

The inputs are continuous, minimum and excursion steel temperature; wet, intermittent or dry duty; SO2, SO3, HCl, HF and moisture; dust load; new build or existing steel; and the fabrication or outage window.

The gate is a Society for Protective Coatings (SSPC) SSPC-SP10 / NACE No. 2 near-white blast with a profile above 3 mils (75 µm), plus process heat at start-up for heat-cured grades. Final heat cured activation is completed during start-up using process heat, while CorrosionGard-160S cures at ambient conditions; a site that cannot meet these is not a fit.

Delivery, Evidence and Cost

Polylloy formulates, supplies, specifies, trains applicators and supervises; certified partners from a network of 15 in 22 countries apply. Refinery fit rests on bulletin listings plus the application-stage Exxon Canada stack. Polylloy has not published a completed refinery case study, so Polylloy's technical team provides project-specific data.

Cost factors are product selection by temperature, chemistry and abrasion; equipment condition, surface preparation and access; area, thickness and losses; labor, inspection, curing and mobilization; freight and duties; and shutdown timing.

Choosing a Coating for Refinery Flue Gas Equipment

Choosing a coating for refinery flue gas equipment comes down to temperature and duty:

• Structures and equipment to 160 °C: CorrosionGard-160S.
• Acid gas ducts, scrubber gas side and chimneys to 225 °C, including HF: FlueGard-225SQC.
• Stacks, ducts and fans to 255 °C: StackGard-255SQW.
• Ducts and chimneys to 425 °C with peaks to 500 °C: FlueGard-425S.
• Hot, dusty ducts to 455 °C: FlueGard-455CHT after technical review.
• Steel beneath refractory: reviewed per project, with the Exxon Canada stack as an application-stage KilnGard-600SCW reference.
• Wetted high-chloride zones, conditions beyond coating limits or mild service: another material.

To book a Coating Performance Review, request a coating evaluation with equipment type, coated area, temperature profile, gas chemistry, abrasion, location and outage or fabrication timing.

FAQs

What High Temperature Coating is Used Inside Refinery Flue Gas Ducts?

It depends on steel temperature, then gas chemistry, abrasion and wet or dry duty. Polylloy bulletins list refinery ducts for FlueGard-225SQC to 225 °C, StackGard-255SQW to 255 °C and FlueGard-425S to 425 °C with peaks to 500 °C. Hotter, dustier ducts can be reviewed for FlueGard-455CHT, rated to 455 °C (850 °F).

Can a Coating Protect Refinery Stacks and Scrubbers?

On the gas side, yes. FlueGard-225SQC is listed for FGD scrubbers, ducts and chimneys in refineries, and StackGard-255SQW for chimneys connected to scrubbers, ducts and fans. Continuously wetted, high-chloride scrubber zones usually stay with rubber, glass-flake linings or nickel alloy, and any coating proposed there needs written confirmation for the conditions.

Is a Refinery High Temperature Coating the Same as a CUI Coating?

No. Corrosion under insulation (CUI) and exterior heat-resistant coatings protect the outside of hot piping and vessels from heat, moisture and atmosphere, while a film inside a flue gas duct or stack also meets SO2, SO3, HCl, dust and acid condensate. Ask for acid gas and condensate data at the operating temperature, not only a heat rating.

Which Petrochemical Corrosion Coating Suits Flue Gas Above 400 °C?

FlueGard-425S is rated from ambient to 425 °C (797 °F) with peaks up to 500 °C, and its bulletin lists gas scrubbers, ducts and chimneys in oil refineries. Its Taber abrasion is below 150 mg, so heavy-dust ducts may suit FlueGard-455CHT, a two-component ceramic coating to 455 °C, after a technical review.

Does Polylloy Have an Oil and Gas Reference?

Yes, at application stage. In 2026 KilnGard-600SCW was shop-applied beneath the refractory on 18 prefabricated sections of an Exxon Canada stack; the project documents placement and coverage, with no in-service performance claim yet. Fit for refinery duty otherwise rests on bulletin listings, and Polylloy's technical team supplies project-specific data for each duty.

Is Coated Carbon Steel an Alternative to 316 Stainless in a Refinery Stack?

It can be. Protected carbon steel may offer a cost-effective alternative to stainless steel where the coating is suitable for the specified service conditions. 316 stainless can pit and crevice-corrode in acidic chloride condensate, so compare both on the same stack, temperatures, chemistry, fabrication scope and evaluation period.

Who Applies Polylloy Coatings at a Refinery?

Certified Polylloy application partners apply them, in the shop on new sections or on site during an outage. Polylloy formulates and supplies the coating, writes the specification, trains the applicator and supervises surface preparation and inspection. For heat-cured grades, final heat cured activation is completed during start-up using process heat.