FGD Scrubber Nickel Alloy Selection Guide 2026

By Shanghai Hangbo Alloy Group Co., Ltd. - China Supplier | ISO 9001:2015 | Est. 2012

Contact: sales@hangboalloy.com | hangbo@nickel-alloy.com | WhatsApp (Lisa): +86 13611656360

Quick Answer: Which Nickel Alloy Should You Specify for an FGD Scrubber?

For most coal-fired and waste-to-energy FGD absorbers, select UNS N10276 (Hastelloy C-276) or Alloy 59 for chloride-rich wetted zones, and leaner 904L or Alloy 20 where chloride stays below roughly 500 mg/L. Ducts, stacks, reheaters and expansion joints usually need C-276 or C-22 cladding rather than solid plate.

Key Takeaways

• Match the alloy to the chloride and fluoride load of each absorber module, not to a plant-wide "FGD grade". One scrubber frequently needs two or three different alloys in different zones.
• C-276 (UNS N10276), Alloy 59, Alloy 22 and Alloy 31 are the workhorses for wetted, chloride-rich absorber service. 904L and Alloy 20 are cost-effective only below roughly 500 mg/L chloride with controlled pH.
• Duplex stainless and leaner austenitics belong in low-chloride, high-erosion gypsum slurry duty, where hardness, abrasion resistance and cost matter more than maximum pitting resistance.
• Alloy-clad plate beats solid nickel-alloy plate economically above roughly 6-8 mm required wall thickness, because cladding places the corrosion barrier only where the aggressive medium actually touches metal.
• Standard designations, not marketing claims, drive acceptance: order to ASTM B575, B906, B424, B625, B443 and B168, and test to ASTM G48, G28 and G36 with EN 10204 3.1 documentation.
• Welding quality controls real service life. Overlay chemistry, iron dilution and interpass temperature matter more to field performance than the base-metal datasheet.

Why Wet FGD Scrubbers Destroy Ordinary Stainless Steel

Ordinary 304L and 316L fail in wet flue gas desulfurization because the process stacks three attack mechanisms on top of one another, and each one overwhelms a lean passive film. Limestone or lime slurry carries chloride that originates in coal, waste feedstock and make-up water; the flue gas supplies SO2, SO3, fluoride and traces of heavy metals; and the absorber sits between roughly 45 and 60 C, which is exactly the temperature window where pitting and crevice initiation accelerate. A 316L shell that passes a hydrostatic test on day one can show through-wall pitting within a few operating seasons once chloride accumulates in a closed-loop water balance.

The controlling variable is chloride concentration in the recirculating slurry liquor, not the chloride content of the coal. Wet scrubbers concentrate dissolved species through evaporation, so a plant burning moderate-chloride coal can still reach 5,000-30,000 mg/L chloride in the absorber sump, and waste-to-energy units that accept PVC-bearing municipal waste routinely run higher. Fluoride behaves even more aggressively at low pH, and in the mildly acidic to near-neutral band typical of inhibited limestone chemistry it attacks passive films that would survive chloride alone. Low pH excursions during upset, oxidation-air interruption or gypsum dewatering problems turn a marginal material into a rapidly failing one.

Erosion compounds the chemistry. Gypsum crystals, limestone grit and fly-ash particles circulate through pumps, spray headers and the mist eliminator at velocities that mechanically strip protective films, so a material that resists chloride but is soft will lose section thickness from the surface inward. The practical consequence is that FGD alloy selection is never a single number such as a PREN value; it is a joint decision about chemistry, temperature, velocity, solids loading and the geometry of crevices that will inevitably exist at welds, flanges, supports and gasketed joints.

Wet FGD also produces low-pH condensate in the "cold" sections downstream of the absorber, where saturated gas cools against uninsulated duct and stack walls. That condensate is a dilute sulfuric and hydrochloric acid mixture that can attack carbon steel and lean stainless from the inside while the outside is dry, which is why ducting and stack linings are frequently the first items to require upgrading even when the absorber itself is satisfactory. Understanding these three attack zones - wetted slurry, wet-dry interface and acid condensate - is the foundation of every selection decision that follows.

Chloride Pitting and Crevice Corrosion: The Primary Alloy Selector

The first selection filter is chloride pitting and crevice corrosion resistance, and the industry-standard method for quantifying it is ASTM G48, with Method C (6% ferric chloride) used to rank critical pitting temperature. For a wet limestone or lime absorber, specify an alloy whose typical critical pitting temperature in ASTM G48 Method C sits comfortably above the maximum metal temperature of the wetted zone, not merely above the nominal operating temperature, because upset conditions and steam-coil or oxidation-air heating can push local metal temperature 10-20 C higher. Where the design includes gaskets, lap joints, support clips or unsealed weld crevices, crevice corrosion resistance becomes the binding constraint, so always compare candidates on the crevice data rather than the free-surface pitting data alone.

Alloy chemistry drives this property through chromium, molybdenum, tungsten and nitrogen. Molybdenum and tungsten raise pitting resistance far more per unit mass than chromium, which is why the Ni-Cr-Mo family - C-276, Alloy 22, Alloy 59, Alloy 31 - occupies the top of the selection ladder for aggressive liquor. Nitrogen additions, as in 254 SMO and the super-duplex grades, raise pitting resistance at lower cost but do not deliver the same crevice performance as a high-molybdenum nickel alloy in the most contaminated liquors. For chloride levels above roughly 1,000 mg/L combined with low pH excursions, or any chloride level in a waste-to-energy liquor containing fluoride and heavy metals, the 6% Mo super-austenitics and duplex grades should be treated as the minimum, not the target.

The tables below compare composition and corrosion performance so that the ranking can be read directly against the design chloride and temperature. All figures marked "typical" are representative commercial values, not guaranteed standard minima; the applicable ASTM or EN product specification governs actual acceptance limits, and the mill should always confirm a value against the certified heat.

Table 1. Nominal composition comparison of FGD candidate alloys (wt%, balance Ni or Fe as noted) - typical values, not standard minima.

Alloy (common name)	UNS / EN W.Nr	Ni	Cr	Mo	Other (typical)	Standard
C-276	UNS N10276 / 2.4819	Balance	15.5	16.0	W 3.7, Fe 5.5	ASTM B575, ASTM B906
C-22	UNS N06022 / 2.4602	Balance	22.0	13.0	W 3.0, Fe 3.0	ASTM B575, ASTM B906
Alloy 59	UNS N06059 / 2.4605	Balance	23.0	16.0	Fe 0.5 max	ASTM B575
Alloy 31	UNS N08031 / 1.4562	31.0	27.0	6.5	N 0.20, Cu 1.2	ASTM B625
904L	UNS N08904 / 1.4539	25.0	20.0	4.5	Cu 1.5	ASTM B625, ASTM B677
254 SMO	UNS S31254 / 1.4547	18.0	20.0	6.1	N 0.20, Cu 0.8	ASTM A240, ASTM B688
Alloy 20	UNS N08020 / 2.4660	34.0	20.0	2.5	Cu 3.5, Nb 0.6	ASTM B463, ASTM B473
2205 duplex	UNS S32205 / 1.4462	5.5	22.0	3.1	N 0.17	ASTM A240
2507 super-duplex	UNS S32750 / 1.4410	7.0	25.0	4.0	N 0.27	ASTM A240
625	UNS N06625 / 2.4856	Balance	21.5	9.0	Nb 3.6	ASTM B443, ASTM B446

Table 2. Chloride and pitting performance ranking for absorber duty - typical commercial values, confirmed by ASTM G48 test methods.

Alloy	PREN (typical)	ASTM G48 Method C CPT, typical	ASTM G48 Method B crevice, typical	Practical chloride guidance for FGD liquor	Standard
316L	about 25	about 20-25 C	about 10-15 C	Marginal; avoid above 200 mg/L	ASTM A240
2205	about 34	about 40-50 C	about 20-25 C	200-1,000 mg/L, neutral pH only	ASTM A240 / G48
904L	about 34	about 45-55 C	about 25-30 C	up to about 500 mg/L with pH control	ASTM B625 / G48
Alloy 20	about 30	about 40-50 C	about 25 C	up to about 500 mg/L, sulfuric service	ASTM B463 / G48
254 SMO	about 43	about 60-70 C	about 35-40 C	500-3,000 mg/L, low fluoride	ASTM A240 / G48
Alloy 31	about 47	about 65-80 C	about 40-45 C	1,000-5,000 mg/L, good all-round	ASTM B625 / G28
C-22	about 60	about 80-90 C	about 45-55 C	above 5,000 mg/L, oxidizing or mixed acid	ASTM B575 / G48, G28
Alloy 59	about 66	about 85-95 C	about 50-60 C	highest chloride, upset-resistant	ASTM B575 / G48, G28
C-276	about 62	about 80-95 C	about 50-60 C	high chloride plus acid and fluoride	ASTM B575 / G48, G36
625	about 51	about 65-80 C	about 35-45 C	high-temperature duct and reheater lining	ASTM B443 / G48

Where stress-corrosion cracking is a credible risk in the presence of chlorides and residual stress, qualification should follow NACE MR0175 / ISO 15156 and, for sour or acid-condensate environments in waste-to-energy service, ASTM G36 for boiling magnesium chloride and ASTM G28 Method A or B for intergranular and ferric-sulfate corrosion. These tests are frequently written into purchase specifications for absorber internals because they detect the sensitized or improperly heat-treated microstructure that a simple corrosion rate test will miss.

Acid Dew Point and the Cold Sections: Ducts, Stacks and Reheaters

Acid dew point corrosion controls the choice of material for everything downstream of the absorber, because sulfur trioxide and residual moisture in the saturated flue gas form a dilute sulfuric acid condensate wherever the metal surface falls below the acid dew point. In practice this means ductwork upstream of the reheater, the wet-dry interface band, and the lower stack, where the wall temperature can drop below 120-150 C depending on SO3 concentration and moisture. For these cold sections, specify an alloy with strong resistance to dilute sulfuric acid across a wide concentration range, and design the lining or cladding to keep the metal surface either clearly above the dew point or clearly protected by a continuous corrosion barrier.

The duct and stack lining choice is usually a decision between solid nickel-alloy plate, roll-bonded or weld-overlay clad plate, and non-metallic linings such as borosilicate glass block or flake-filled resin. Metallic linings - C-276, C-22, Alloy 59, Alloy 31 or 625, in thicknesses typically 1.5-3.0 mm as clad or liner sheet - tolerate the dilute acid, resist thermal cycling and accept mechanical damage better than many non-metallic systems, but they demand high-integrity welding of every seam and penetration. Where the condensate is strongly oxidizing or contains chlorides from the gas stream, the high-molybdenum Ni-Cr-Mo grades are the safe default; where the condensate is dilute and temperatures stay moderate, a 6% Mo super-austenitic can be acceptable.

Reheaters deserve separate treatment because they combine the two attack modes. A tubular or steam-coil reheater sees wet, acid-loaded gas on the outside and hot steam on the inside, so the metal temperature is a design variable that determines whether the gas-side surface sits above or below the dew point. For flue-gas reheaters, nickel-chromium alloys such as 625, C-276 and C-22 are common choices for the gas-side surfaces, tube supports and the first few metres of outlet ducting, because they tolerate both dilute acid condensate and periodic dry operation. The design intent should always be stated as a minimum metal temperature above dew point, with the alloy selection as the fallback when that cannot be guaranteed across all load cases.

Table 3. Environment severity matrix for scrubber zones - guidance based on typical operating conditions; verify against project design data.

Scrubber zone	Typical environment	Typical metal temperature	Minimum acceptable alloy	Preferred alloy	Standard
Absorber sump, slurry wetted	pH 4.5-6, high chloride, high solids	45-60 C	254 SMO	C-276, Alloy 59	ASTM B575, G48
Spray header and nozzles	High velocity, erosion plus chloride	45-60 C	Alloy 31	C-276, Alloy 59	ASTM B575
Mist eliminator, wet zone	Acid mist, chloride, low pH	50-60 C	254 SMO	C-22, C-276	ASTM B575, G28
Mist eliminator wash zone	Fluctuating pH, erosive wash	50-60 C	904L	Alloy 31, C-276	ASTM B625
Inlet duct, wet-dry interface	Concentrating acid, chloride salts	60-160 C	Alloy 31	C-276 clad, 625 clad	ASTM B575, B443
Outlet duct and stack, below dew point	Dilute H2SO4 + HCl condensate	60-150 C	254 SMO	C-276 clad, Alloy 59 clad	ASTM B575, B906
Reheater, gas side	Acid condensate plus dry cycling	100-200 C	625	C-276, C-22	ASTM B443, B575
Expansion joint, wetted	Flexing, chloride, crevice at flanges	45-160 C	254 SMO	C-276, Alloy 20	ASTM B575, B463
Oxidation-air sparger	Air, low pH, chloride	50-60 C	904L	Alloy 31, C-276	ASTM B625
Gypsum dewatering, low chloride	Erosive solids, near-neutral pH	40-60 C	2205	2507, Alloy 20	ASTM A240

Gypsum Slurry Erosion and the Absorber Vessel

Gypsum slurry erosion sets the second selection filter after corrosion, and in the absorber vessel, recirculation piping and spray headers it frequently decides the final material where two alloys have comparable corrosion resistance. Limestone and gypsum solids circulate at 15-25% by weight in many designs, with particle sizes that blunt softer alloys and mechanically remove protective passive films at impingement angles around 30-45 degrees. A soft, highly corrosion-resistant alloy can therefore perform worse than a harder alloy with moderate corrosion resistance in a high-velocity, high-solids location, which is why erosion allowance, velocity limits and nozzle geometry belong in the same conversation as alloy chemistry. The practical rule is to combine corrosion data with hardness, yield strength and a design velocity ceiling, and to design for the erosion allowance explicitly rather than relying on the material alone.

Absorber vessel construction usually follows one of three patterns: carbon steel with a protective lining, carbon steel with a corrosion-resistant alloy clad or overlay on all wetted surfaces, or solid stainless or nickel-alloy plate for small units and severe service. For large vessels, lined or clad carbon steel dominates on cost, with the alloy barrier confined to the wetted surface and to the critical zones around the slurry pool, agitator supports, inlet gas penetrations and the oxidation-air sparger. Design stress for these vessels is taken from the applicable pressure-vessel code using the allowable stress of the structural material, so the corrosion barrier does not need to carry mechanical load; the mechanical data for the liner or clad layer is nonetheless required to confirm it survives forming, welding and thermal cycling without cracking.

Erosion also dictates where solid high-grade alloy is genuinely unavoidable. Spray header manifolds, nozzle bosses, pump casings and elbows at the discharge of recirculation pumps see the combination of high velocity, high solids and chloride chemistry that no lean material survives, so they are specified in C-276, Alloy 59 or Alloy 31 for the wetted contact surfaces. Conversely, gypsum dewatering equipment, hydrocyclones and thickener internals operate at lower chloride and moderate pH, where duplex 2205 or super-duplex 2507 delivers adequate corrosion resistance with much better erosion performance per dollar than a lean austenitic. Matching mechanical performance to the erosion regime, rather than simply upgrading alloy everywhere, is what keeps an FGD materials package affordable.

Table 4. Mechanical properties at room and elevated temperature - typical annealed values, not standard minima; refer to the governing ASTM specification for acceptance limits.

Alloy	UNS	Rp0.2 at 20 C, typical	Rm at 20 C, typical	Elongation, typical	Rp0.2 at 200 C, typical	Rp0.2 at 300 C, typical	Standard
C-276 sheet	N10276	355 MPa	760 MPa	55%	about 300 MPa	about 275 MPa	ASTM B575, E8, E21
Alloy 59 sheet	N06059	380 MPa	760 MPa	50%	about 320 MPa	about 290 MPa	ASTM B575, E8, E21
C-22 sheet	N06022	340 MPa	745 MPa	55%	about 295 MPa	about 270 MPa	ASTM B575, E8, E21
Alloy 31 plate	N08031	300 MPa	680 MPa	45%	about 240 MPa	about 215 MPa	ASTM B625, E8
904L plate	N08904	240 MPa	560 MPa	45%	about 190 MPa	about 175 MPa	ASTM B625, E8
254 SMO plate	S31254	300 MPa	650 MPa	40%	about 230 MPa	about 205 MPa	ASTM A240, E8
Alloy 20 plate	N08020	240 MPa	550 MPa	40%	about 185 MPa	about 170 MPa	ASTM B463, E8
2205 plate	S32205	450 MPa	620 MPa	25%	about 350 MPa	about 320 MPa	ASTM A240, E8
2507 plate	S32750	550 MPa	795 MPa	25%	about 440 MPa	about 400 MPa	ASTM A240, E8
625 plate	N06625	415 MPa	830 MPa	42%	about 350 MPa	about 330 MPa	ASTM B443, B446, E8

Component-by-Component Selection: Spray Headers, Mist Eliminators, Duct Linings and Expansion Joints

Component-level selection is where a general alloy strategy becomes a procurement list, and the correct answer differs for each internal because the local chloride level, velocity, temperature and crevice geometry differ. The absorber shell and slurry pool see the highest chloride combined with moderate velocity, the spray headers and nozzles see the highest velocity and impingement erosion, the mist eliminators see acid mist and droplets at a low pH, the duct linings see acid condensate at the wet-dry interface, and the expansion joints see flexing plus crevice attack at every flange face. Designing each component against its own worst case, then verifying that adjacent components do not set up a galvanic couple, is the reliable method.

Spray headers and their nozzles are the most demanding wetted components because erosion and corrosion act simultaneously. Solid C-276 or Alloy 59 headers with reinforced nozzle bosses are standard practice for high-chloride absorbers, while Alloy 31 and 6% Mo super-austenitics are acceptable where chloride and solids are moderate. Mist eliminator elements in wet-duty positions require an alloy that tolerates dilute acid at low pH without crevice attack, so C-22 and C-276 are common, and the support frames and wash headers must be at least as resistant as the elements themselves to avoid preferential failure of the structure. Where the mist eliminator operates with intermittent wash and fluctuating pH, Alloy 31 is a frequent compromise between performance and cost.

Duct linings and expansion joints deserve early attention because they are easy to underspecify and expensive to remediate. Inlet ducting at the wet-dry interface concentrates chloride salts and acid as the gas evaporates moisture, so C-276 or 625 clad plate is the usual choice for the first few metres, transitioning to a less costly material further downstream. Expansion joints combine a flexible element with bolted or welded flanges, creating crevices that a lean material cannot survive, so the wetted-side barrier is typically C-276, Alloy 20 or a high-molybdenum super-austenitic, with the fabric construction designed to prevent condensate pooling. Reheater tubes, supports and outlet transitions see acid condensate plus thermal cycling, so 625, C-276 and C-22 remain the mainstream selections for the gas-side surfaces.

Table 5. Application and selection by scrubber component - recommended and alternative alloys based on typical wet FGD operating conditions.

Component	Governing attack mode	Recommended alloy	Acceptable alternative	Avoid	Standard
Absorber shell, wetted	Chloride pitting, acid	C-276 or Alloy 59 clad	Alloy 31 clad, 254 SMO	316L, 317L	ASTM B575, B906
Absorber sump liner	Chloride, solids, low pH	Alloy 59 or C-276	Alloy 31	304L, carbon steel bare	ASTM B575, B625
Spray header and nozzles	Erosion plus chloride	C-276	Alloy 59, Alloy 31	316L, 904L at high solids	ASTM B575, B625
Mist eliminator elements	Acid mist, low pH, chloride	C-22 or C-276	Alloy 31	316L, 2205	ASTM B575, G28
Mist eliminator support frame	Crevice plus acid mist	C-276	Alloy 31	304L bolted joints	ASTM B575
Duct lining, wet-dry interface	Concentrating acid, chloride salts	C-276 clad	625 clad, Alloy 31 clad	Carbon steel bare, 316L	ASTM B575, B443
Outlet duct and stack lining	Dilute H2SO4 plus HCl	C-276 clad	Alloy 59 clad, 625 clad	316L, Corten	ASTM B575, B906
Expansion joint, wetted side	Crevice, flexing, chloride	C-276 or Alloy 20	254 SMO, Alloy 31	316L bellows	ASTM B575, B463
Reheater tube, gas side	Acid condensate, thermal cycle	625	C-276, C-22	321, 304H	ASTM B443, B444
Oxidation-air sparger	Low pH, chloride, aeration	Alloy 31	C-276, 254 SMO	316L	ASTM B625
Gypsum dewatering internals	Erosion, low chloride	2205 or 2507	Alloy 20	316L at high velocity	ASTM A240, B463

Alloy-Clad vs Solid Plate: The Economics of Thick-Wall Nickel Alloys

Alloy-clad plate is usually the right answer for FGD vessels and ducting once the required wall thickness exceeds roughly 6-8 mm, because the structural thickness is supplied by affordable carbon or low-alloy steel and the corrosion resistance is supplied by a 1.5-3.0 mm metallurgically bonded alloy layer. Solid nickel-alloy plate is the exception rather than the rule: it makes sense for thin-walled components, for small vessels, for highly stressed parts where a dissimilar-metal joint is undesirable, and for cases where the alloy layer thickness needed would approach the total wall thickness anyway. Conducting the comparison on a cost-per-square-metre-of-wetted-surface basis, rather than on cost per kilogram of alloy, exposes the real economics and usually favours cladding by a wide margin for large absorbers.

Roll-bonded clad plate is produced by assembling an alloy plate on a carbon or low-alloy steel backing plate, welding the edges, evacuating the gap and hot-rolling the assembly so that the interface diffuses into a continuous metallurgical bond. Weld-overlay cladding applies the alloy by submerged-arc or electroslag strip welding, typically in one or two layers, and is common for vessels and heads that cannot be economically roll-bonded. Both routes deliver a wetted surface whose chemistry meets the alloy specification, but the surrounding fabrication must respect the dilution zone and the mechanical properties of the backing steel; the two systems are not interchangeable in fabrication sequence, and the choice depends on the shop's cladding capability and the component geometry.

Explosion-bonded clad is a third option that suits thick backing plates and components where hot rolling is impractical. In all three cases, the specification should state the cladding standard, the minimum clad thickness, the bond integrity requirement, the shear or ultrasonic test method, the chemical composition of both layers, and the welding of the clad restoration including the filler metal for the alloy layer and the transition joint if required. The five-system cross-reference below helps convert a US or European alloy designation into the Chinese, Japanese or Russian equivalent routinely used in international tender documents and in mill test certificates.

Table 6. Five-system standard cross-reference for FGD candidate alloys - approximate equivalences, confirm exact grade and product form against the governing standard before ordering.

Common name	US UNS / ASTM	GB (China)	JIS (Japan)	DIN / EN (W.Nr)	GOST (Russia / CIS)
C-276	UNS N10276, ASTM B575	NS3304, GB/T 15007	NCF 276, JIS G 4902	2.4819, EN 10204 documentation	KhN65MV (ХН65МВ)
C-22	UNS N06022, ASTM B575	GB/T 15007 NS3306 (similar)	JIS G 4902 (equivalent pending)	2.4602	near-analogue per GOST 5632
Alloy 59	UNS N06059, ASTM B575	GB/T 15007 (order by chemistry, similar)	JIS G 4902 (equivalent pending)	2.4605	near-analogue per GOST 5632
Alloy 31	UNS N08031, ASTM B625	GB/T 15007 NS1405 (similar)	JIS G 4901 family (similar)	1.4562	near-analogue per GOST 5632
904L	UNS N08904, ASTM B625	00Cr20Ni25Mo4.5Cu, GB/T 20878	SUS 890L, JIS G 4304 / G 4305	1.4539	06KhN28MDT (06ХН28МДТ)
254 SMO	UNS S31254, ASTM A240	00Cr20Ni18Mo6CuN, GB/T 20878	SUS 312L type (similar)	1.4547	near-analogue per GOST 5632
Alloy 20	UNS N08020, ASTM B463	NS143, GB/T 15007	JIS G 4901 family (similar)	2.4660	near-analogue per GOST 5632
625	UNS N06625, ASTM B443	GH3625, GB/T 14992	NCF 625, JIS G 4901	2.4856	KhN75MBTYu type (similar)
800	UNS N08800, ASTM B409	NS111, GB/T 15007	NCF 800, JIS G 4901	1.4876	KhN32T (ХН32Т)
825	UNS N08825, ASTM B424	NS142, GB/T 15007	NCF 825, JIS G 4901	2.4858	KhN38VT type (similar)
Monel 400	UNS N04400, ASTM B127	NCu30, GB/T 15007	JIS G 4911 (NW 4400)	2.4360	NMZhMts 28-2.5-1.5
2205 duplex	UNS S32205, ASTM A240	00Cr22Ni5Mo3N, GB/T 20878	SUS 329J3L, JIS G 4304	1.4462	near-analogue per GOST 5632

Fabrication, Welding and Quality Documentation for FGD Alloys

Fabrication quality determines whether a correctly selected alloy actually delivers its corrosion resistance in service, because most early FGD failures occur at welds, heat-affected zones and crevices rather than in parent plate. Nickel alloys are more sluggish and less fluid than stainless steel, so they need more careful joint preparation, controlled heat input, low interpass temperature and clean, dedicated tooling to avoid iron contamination. Every wetted weld on a C-276, Alloy 59 or Alloy 31 surface should be made with matching or over-alloyed filler metal, with the root and cap chemistry verified, and with the weld profile dressed smooth to eliminate the crevices and undercuts that become pit initiation sites. Where clad plate is used, the clad restoration weld must be made with the alloy filler before the backing weld is completed, so that the stainless or carbon-steel weld metal is never exposed to the process liquor.

Heat treatment is equally critical and is frequently misunderstood. The Ni-Cr-Mo alloys are supplied in the solution-annealed condition and should not be stress-relief annealed at intermediate temperatures, which would precipitate intermetallic phases and destroy both corrosion resistance and toughness; when post-weld heat treatment of the backing steel is unavoidable, it must be controlled so that the alloy layer does not enter the sensitization range, often by using a low-carbon or low-alloy backing that permits lower treatment temperatures. Super-austenitics such as 254 SMO must not be held in the 600-1,000 C sigma-forming range, and duplex grades require controlled cooling to preserve the ferrite-austenite balance. The heat-treatment column below states the normal supply condition and the temperatures to avoid.

Table 7. Heat treatment, supply condition and temperatures to avoid - typical mill practice; the governing ASTM or EN specification controls acceptance.

Alloy	Supply condition	Recommended anneal	Cooling	Hold temperatures to avoid	Standard
C-276	Solution annealed	1,050-1,120 C	Rapid water quench	600-900 C	ASTM B575
Alloy 59	Solution annealed	1,100-1,180 C	Rapid water quench	600-900 C	ASTM B575
C-22	Solution annealed	1,100-1,150 C	Rapid water quench	600-900 C	ASTM B575
Alloy 31	Solution annealed	1,100-1,180 C	Water quench	600-950 C	ASTM B625
904L	Solution annealed	1,050-1,100 C	Water quench	550-900 C	ASTM B625
254 SMO	Solution annealed	1,150-1,200 C	Water quench	600-1,000 C	ASTM A240
Alloy 20	Solution annealed	940-1,010 C	Water quench	500-900 C	ASTM B463
2205	Solution annealed	1,020-1,100 C	Water quench	600-1,000 C	ASTM A240
2507	Solution annealed	1,025-1,125 C	Water quench	600-1,000 C	ASTM A240
625	Solution annealed	1,090-1,200 C	Rapid air or water	600-900 C	ASTM B443

Table 8. Fabrication and welding guidance for FGD nickel alloys - practical shop practice, verify against the qualified welding procedure specification.

Alloy	Filler metal (AWS A5.14 or A5.9)	Preferred processes	Interpass temperature guide	Key fabrication notes	Standard
C-276	ERNiCrMo-4	GTAW, GMAW, SMAW	below 150 C	Dedicated tooling, low iron dilution	ASTM B575, AWS A5.14
Alloy 59	ERNiCrMo-13	GTAW, GMAW	below 120 C	High-purity surface, no preheat	ASTM B575
C-22	ERNiCrMo-10	GTAW, GMAW, SMAW	below 150 C	Cleaning between passes	ASTM B575
Alloy 31	ERNiCrMo-13 or ERNiCrMo-4	GTAW, SMAW	below 150 C	Control nitrogen loss in HAZ	ASTM B625
904L	ER385 (A5.9)	GTAW, SMAW	below 150 C	Low heat input, no PWHT	ASTM B625, B677
254 SMO	ERNiCrMo-3 or 625-type	GTAW, SMAW	below 150 C	Avoid sigma range, cool fast	ASTM A240
Alloy 20	ER320LR (A5.9)	GTAW, SMAW	below 150 C	Niobium-stabilized filler	ASTM B463, B473
2205	ER2209	GTAW, SMAW	below 150 C	Maintain phase balance	ASTM A240, A923
2507	ER2594	GTAW, SMAW	below 150 C	Higher heat input than 2205	ASTM A240, A923
625	ERNiCrMo-3	GTAW, GMAW, SAW	below 150 C	Common for overlay cladding	ASTM B443, B446

Documentation is part of the material, not an afterthought. FGD packages for international projects almost always require EN 10204 3.1 mill test certificates linking heat number to chemical composition, mechanical test results and any corrosion or intergranular test results, plus traceability from plate slab to finished component, welding procedure qualification records and welder performance qualification records. Purchasers should also confirm positive material identification on receipt, because mixed material in a scrubber is both a corrosion risk and a common cause of weldability problems. Specifying the required test methods up front - ASTM G48 for pitting and crevice, ASTM G28 Method A or B for intergranular attack, ASTM G36 for stress-corrosion cracking screening, ASTM E8 and E21 for mechanical properties, and NACE MR0175 / ISO 15156 where sour or acidic condensate service applies - removes ambiguity at the point of acceptance. Buyers evaluating a mill's capability can review documented material and process controls, and Shanghai Hangbo Alloy Group publishes applicable test information alongside its product ranges for absorber, ducting and reheater applications.

Common Selection Mistakes and a Practical Decision Sequence

The most expensive FGD material mistakes are systematic rather than random, and they can be avoided by applying a short, disciplined decision sequence. The first mistake is selecting one alloy for the whole scrubber: a "C-276 everywhere" specification wastes money on low-chloride dewatering equipment, while a "316L everywhere" specification guarantees early failure in the absorber and duct lining. The second mistake is reading chlorine from the coal analysis instead of measuring chloride in the recirculating liquor, which understates the design value by an order of magnitude. The third is ignoring the wet-dry interface, where concentrating salts and acid create the most aggressive local chemistry in the entire system. The fourth is specifying the alloy correctly but allowing unprotected crevices at bolted joints and support clips, which reintroduce the failure mode the alloy was chosen to prevent. The fifth is accepting a mill certificate without verifying that the corrosion tests were actually performed on the supplied heat rather than on a generic heat lot.

A practical decision sequence resolves most projects in five steps. First, define the water chemistry envelope: maximum and normal chloride, fluoride, pH range, solids content and temperature for each zone, including upset conditions. Second, define the mechanical and erosion conditions: velocity limits, impingement angles and solids loading for each component. Third, apply ASTM G48 and related corrosion data to select the corrosion class, then adjust for erosion using hardness and strength data. Fourth, decide construction method - solid plate, roll-bonded clad, weld overlay or lined carbon steel - on a cost-per-wetted-square-metre basis. Fifth, write a specification that fixes the standard designation, product form, surface finish, welding filler metals, corrosion test methods and documentation requirements in one document, so that the mill, fabricator and quality inspector all work from the same requirements.

Applying that sequence typically produces a mixed bill of materials: C-276 or Alloy 59 for the absorber wetted surfaces, spray headers and mist eliminator frames; Alloy 31 or 254 SMO for intermediate chloride zones and some duct sections; 904L or Alloy 20 for lower-chloride wash and low-temperature acid service; duplex 2205 or 2507 for gypsum dewatering; and 625 or C-276 cladding for reheaters and hot-side duct transitions. That outcome is normal and desirable. It reflects the fact that an FGD scrubber is a set of different chemical environments sharing one structure, and that a correctly differentiated materials list is both safer and cheaper than a uniform one. Working with a mill that can supply the full range of nickel alloys, super-austenitics, duplex stainless and clad plate from one source simplifies both the qualification effort and the traceability chain.

Table 9. Indicative price reference for FGD candidate alloys - reference ranges only, 2026, EXW Shanghai, USD/kg; not a quotation and subject to nickel, molybdenum and chromium market movement, product form, quantity and specification.

Alloy	Plate and sheet, reference range	Bar and tube, reference range	Notes on price drivers	Standard
C-276	34-48	42-60	Highest molybdenum plus tungsten; price tracks Mo closely	ASTM B575
Alloy 59	36-52	44-64	Highest alloy content in the Ni-Cr-Mo family	ASTM B575
C-22	32-45	40-56	Slightly lower Mo than C-276, similar W	ASTM B575
Alloy 31	18-27	24-36	Iron-bearing nickel alloy, lower Ni content	ASTM B625
904L	9-14	13-20	Molybdenum and copper driven	ASTM B625
254 SMO	14-20	18-27	6% Mo plus nitrogen premium	ASTM A240
Alloy 20	13-19	17-25	Copper and niobium additions	ASTM B463
2205 duplex	4.5-7.0	6-10	Low nickel, nitrogen strengthened	ASTM A240
2507 super-duplex	7-11	10-16	Higher Cr, Mo and N	ASTM A240
625	30-42	36-52	Niobium addition plus high nickel	ASTM B443
C-276 clad plate (3 mm on carbon steel)	24-36 per kg of assembly	-	Priced on clad area, not alloy mass	ASTM B906, B575

All price figures in Table 9 are reference ranges only for 2026, EXW Shanghai, USD/kg, provided for budgetary comparison and not as a quotation. Contact the mill for a firm offer against a defined specification and quantity.

Standard Index

Table 10. Standard index - specifications referenced in this guide and what they cover.

Standard	Title or scope	Covers	Form
ASTM B575	Low-carbon Ni-Cr-Mo and Ni-Cr-Mo-Cu alloy plate, sheet and strip	C-276, C-22, Alloy 59 chemistry and properties	Plate, sheet, strip
ASTM B906	Standard specification for general requirements for flat-rolled nickel and nickel alloy plate, sheet and strip	Generic requirements shared by flat-rolled nickel alloy specs	Plate, sheet, strip
ASTM B424	Ni-Fe-Cr-Mo-Cu alloy plate, sheet and strip	Alloy 825 and related Ni-Fe-Cr-Mo-Cu grades	Plate, sheet, strip
ASTM B625	Ni-Fe-Cr-Mo-Cu-N low-carbon alloys and Ni-Cr-Mo-N alloys	Alloy 31, 904L-class plate and sheet	Plate, sheet, strip
ASTM B443	Ni-Cr-Mo-Nb alloy plate, sheet and strip	Alloy 625 flat products	Plate, sheet, strip
ASTM B168	Ni-Cr-Fe alloy plate, sheet and strip	600, 601, 602 and related Ni-Cr-Fe grades	Plate, sheet, strip
ASTM B463	UNS N08020 alloy plate, sheet and strip	Alloy 20 flat products	Plate, sheet, strip
ASTM B473	UNS N08020, N08024, N08026 bar and wire	Alloy 20 bar, wire and fasteners	Bar, wire
ASTM B677	UNS N08904 and N08926 seamless and welded pipe	904L and 6% Mo pipe	Pipe
ASTM B688	Ni-Cr-Mo-N alloy plate, sheet and strip	254 SMO flat products	Plate, sheet, strip
ASTM B446	Ni-Cr-Mo-Nb alloy bar, forgings and forging stock	625 bar stock and forgings	Bar, forging
ASTM A240	Chromium and chromium-nickel stainless steel plate, sheet and strip for pressure vessels	2205, 2507, 316L and duplex flat products	Plate, sheet, strip
ASTM G48	Pitting and crevice corrosion resistance of stainless steels and related alloys by use of ferric chloride solution	Critical pitting and crevice temperature, Methods A-C	Test method
ASTM G28	Detecting susceptibility to intergranular corrosion in wrought, nickel-rich, chromium-bearing alloys	Intergranular attack, Methods A and B	Test method
ASTM G36	Evaluating stress-corrosion-cracking resistance of metals and alloys in boiling magnesium chloride solution	SCC screening for austenitic alloys	Test method
ASTM E8	Tension testing of metallic materials	Room-temperature tensile properties	Test method
ASTM E21	Elevated-temperature tension testing of metallic materials	Tensile properties at elevated temperature	Test method
NACE MR0175 / ISO 15156	Materials for use in H2S-containing environments in oil and gas production	SCC and hardness limits where sour service applies	Materials standard
EN 10204	Metallic products - types of inspection documents	3.1 mill test certificate and traceability	Documentation
GB/T 14992	Classification and designation of superalloys	Chinese GH and related heat-resisting grades	Grade designation
GB/T 15007	Corrosion-resistant alloy grades	Chinese NS grades and equivalences	Grade designation
GB/T 20878	Stainless and heat-resisting steels - designation and chemical composition	Chinese stainless designations such as 00Cr20Ni25Mo4.5Cu	Grade designation
JIS G 4901	Corrosion-resistant and heat-resistant nickel-chromium-iron alloy bars, plates and tubes	NCF 600, 625, 800, 825 family	Bar, plate, tube
JIS G 4902	Corrosion-resistant and heat-resistant nickel-chromium-molybdenum alloy plate, sheet and strip	NCF 276 and Ni-Cr-Mo flat products	Plate, sheet, strip
JIS G 4903	Corrosion-resistant and heat-resistant nickel-chromium-iron alloy seamless pipes and tubes	NCF 600 and 800 tube products	Seamless tube
JIS G 4904	Corrosion-resistant and heat-resistant nickel-chromium-iron-molybdenum alloy plate, sheet and strip	NCF 825-class flat products	Plate, sheet, strip
DIN / EN 10204 and W.Nr designations	European material number system and inspection documents	W.Nr 2.4819, 2.4856, 2.4858 and EN 10204 certificates	Grade designation and documentation
GOST 5632	Corrosion-resistant, heat-resistant and heat-proof steels and alloys	Russian designations such as KhN65MV and 06KhN28MDT	Grade designation

FAQ

Q1: Which nickel alloy is best for a wet limestone FGD absorber?

For most wet limestone and lime absorbers, C-276 (UNS N10276) is the safest single choice for wetted internals, with Alloy 59 and Alloy 22 as equally credible alternatives. These Ni-Cr-Mo alloys combine high molybdenum and tungsten content with enough chromium to resist both chloride pitting and dilute sulfuric acid, and their typical ASTM G48 Method C critical pitting temperatures sit far above the 45-60 C metal temperatures found in an absorber sump. The selection is not automatic, though: a low-chloride absorber with good pH control and minimal solids may run perfectly well on Alloy 31 or even a 6% Mo super-austenitic for a fraction of the cost. The deciding inputs are maximum chloride in the recirculating liquor, fluoride content, pH range, solids loading and maximum metal temperature, not the name of the coal or the size of the plant. Where waste-to-energy feedstock introduces chloride, fluoride and heavy metals together, err toward the high-molybdenum end of the family. Our Hastelloy C-276 and Alloy 59 product range covers plate, sheet, bar and tube in the flat-rolled and tubular forms most scrubber fabricators require, and the mill can supply corrosion test data against ASTM G48 and ASTM G28 on request.

Q2: When is 904L or Alloy 20 good enough instead of C-276?

904L and Alloy 20 are genuinely cost-effective when chloride in the recirculating liquor stays below roughly 500 mg/L, pH is controlled in the mildly acidic to neutral band, and velocities are moderate. In that window both alloys resist chloride pitting and general corrosion adequately, and they cost roughly one-third of a high-molybdenum nickel alloy. The trap is relying on feedwater or coal analysis rather than measured liquor chloride, because wet scrubbers concentrate chloride by evaporation and can reach several thousand mg/L even from moderate-chloride input. A second trap is upset operation: pH excursions, oxidation-air interruption or gypsum dewatering problems can drop the liquor into a range where 904L and Alloy 20 pit rapidly. If the design cannot guarantee the chloride and pH envelope across all load cases, or if the plant burns waste-derived fuel, the savings are illusory. Many operators use these alloys in lower-risk positions such as wash-water systems, lower-temperature acid service and non-wetted supports, while reserving C-276 or Alloy 59 for the absorber sump and spray headers. Our stainless and super-austenitic product range includes 904L, 254 SMO and duplex grades in plate, bar and tube for exactly this differentiated approach.

Q3: How do I decide between Alloy C-276, Alloy 22 and Alloy 59?

The three alloys sit close together on the Ni-Cr-Mo ladder, and the choice usually comes down to the specific chemistry of the liquor rather than a large performance gap. C-276 (UNS N10276) offers very high molybdenum plus tungsten and is the established default for chloride-rich, mildly reducing absorber service. C-22 (UNS N06022) raises chromium to about 22% with slightly lower molybdenum, which improves performance in oxidizing media and mixed acid condensate, and it is often favoured for outlet ducting and acid-laden gas paths. Alloy 59 (UNS N06059) has the highest combination of chromium and molybdenum with minimal iron, giving the best overall corrosion resistance and the strongest resistance to upset chemistry, at the highest price. In practice, specify C-276 for the absorber wetted surfaces and spray headers, C-22 or 625 for hot-side ducting and reheaters, and Alloy 59 where chloride and fluoride are both high or where upset conditions are frequent. Confirm the final choice against ASTM G48 crevice data and, where relevant, ASTM G28 results on the actual production heat. Our Inconel and Ni-Cr-Mo grade portfolio covers 600-series and 625 products used alongside these alloys in duct and reheater construction.

Q4: What chloride level requires a nickel alloy instead of duplex stainless?

As a working rule, duplex 2205 is suitable up to roughly 200-1,000 mg/L chloride at near-neutral pH and moderate temperature, super-duplex 2507 extends that to perhaps 2,000-3,000 mg/L, and 6% Mo super-austenitics such as 254 SMO cover roughly 500-3,000 mg/L with better crevice performance. Above about 3,000-5,000 mg/L, or at any chloride level with pH excursions, fluoride or elevated temperature, the Ni-Cr-Mo nickel alloys become the reliable choice. These thresholds are guidance, not standard minima: the governing evidence is the ASTM G48 critical pitting and crevice temperature for the specific alloy in the specific chemistry, compared against the maximum metal temperature of the component. Because crevices exist at gaskets, support clips and unsealed welds, always compare candidates on crevice data rather than free-surface pitting data, and add a margin for upset conditions. Waste-to-energy liquors should be treated as more aggressive than their chloride number alone suggests. For high-chloride absorber zones, see our nickel alloy grade listing.

Q5: Why do FGD duct linings and stacks fail even when the absorber is fine?

Duct and stack failures usually trace to acid dew point corrosion rather than to the absorber chemistry. Saturated flue gas leaving the absorber carries residual moisture and sulfur trioxide, which form dilute sulfuric acid condensate wherever the metal surface falls below the acid dew point, typically in the 120-150 C band depending on SO3 concentration. The most aggressive location is the wet-dry interface, where evaporating moisture concentrates chloride salts and acid into a thin, highly corrosive film. Carbon steel and lean stainless steels that were acceptable upstream cannot tolerate this condensate, so linings must be upgraded to C-276, C-22, Alloy 59 or 625, either as solid sheet or as roll-bonded or weld-overlay clad plate. The practical design rules are to keep the metal surface either clearly above the dew point or fully protected by a continuous corrosion barrier, to eliminate crevices at support attachments, and to insulate or heat-trace sections where condensation cannot be prevented. The latest field experience from international wet FGD projects is summarised in our industry upgrade notes.

Q6: Should I use solid alloy plate or alloy-clad plate for the absorber vessel?

Use alloy-clad or weld-overlay plate whenever the required structural wall thickness exceeds roughly 6-8 mm, which is the case for almost every full-size absorber vessel and large duct section. Cladding places a 1.5-3.0 mm corrosion-resistant alloy layer only on the wetted surface and lets affordable carbon or low-alloy steel carry the structural load, so the cost comparison should be made per square metre of wetted surface rather than per kilogram of alloy. Solid nickel-alloy plate makes sense for thin-walled components, small vessels, highly stressed parts where a dissimilar-metal joint is undesirable, and cases where the alloy layer thickness would approach the total wall thickness anyway. Roll-bonded clad, explosion-bonded clad and weld overlay each suit different geometries and shop capabilities, and the specification must state the cladding standard, minimum clad thickness, bond integrity test, clad restoration welding sequence and filler metals. Our guidance article on choosing between solid and clad nickel alloy plate explains the fabrication implications in more detail.

Q7: What is the best alloy for spray headers and mist eliminators?

Spray headers and nozzles see the most severe combination in the scrubber: high chloride, high velocity and erosive gypsum solids impinging at angles that strip passive films. Solid C-276 is the standard choice for high-chloride absorbers, with Alloy 59 and Alloy 31 as acceptable alternatives where chloride and solids are moderate. Mist eliminator elements operate in acid mist at low pH and must also resist crevice attack at the element-to-frame connections, so C-22 and C-276 are common, with Alloy 31 used where wash cycles keep chloride moderate. The support frames and wash headers must be at least as corrosion resistant as the elements themselves, because preferential failure of the structure is a frequent and avoidable problem. Nozzle bore geometry and header velocity should be designed to limit impingement, since no alloy survives unlimited erosive attack. Both components benefit from being produced from the same qualified heat with corrosion test data attached, which simplifies acceptance and field traceability.

Q8: How is acid dew point corrosion handled in reheaters and outlet ducting?

Reheaters are handled by combining a temperature strategy with the right alloy. The primary control is to keep the gas-side metal temperature above the acid dew point across all load cases, usually by reheating the saturated gas or by maintaining the outlet duct wall temperature with insulation or trace heating. When that cannot be guaranteed, the gas-side surfaces, tube supports and the first few metres of outlet ducting are made from nickel-chromium alloys such as 625, C-276 or C-22, which tolerate dilute acid condensate and periodic dry operation. The design intent should be stated explicitly as a minimum metal temperature above dew point, with alloy selection as the fallback for excursions. Outlet ducting below the dew point is normally protected with C-276, Alloy 59 or 625 cladding on a carbon-steel structural shell. Expansion joints and instrumentation penetrations are the usual leak paths and should be reviewed at the same time.

Q9: What corrosion test methods should I specify for FGD alloys?

Specify the tests that reproduce the failure modes you actually fear, and require them on the supplied heat. ASTM G48 Method C ranks critical pitting temperature and Method B ranks crevice corrosion in ferric chloride, which is the most useful screen for absorber and duct service. ASTM G28 Method A or B detects intergranular attack and is valuable for verifying that flat products and welds are correctly solution annealed. ASTM G36 screens resistance to stress-corrosion cracking in boiling magnesium chloride and is worth including where residual stress and chlorides coexist. Where sour or acidic condensate service applies, NACE MR0175 / ISO 15156 sets hardness and material limits. Mechanical properties should be confirmed to ASTM E8 at room temperature and ASTM E21 at elevated temperature, and all deliveries should be supported by EN 10204 3.1 mill test certificates with heat-number traceability. Hangbo Alloy supplies FGD-related products with the applicable test documentation, which removes ambiguity at final inspection.

Q10: How does gypsum slurry erosion change the alloy choice?

Erosion shifts the decision from corrosion resistance alone toward a combined assessment of hardness, yield strength, velocity and solids loading. Gypsum and limestone particles circulating at 15-25% solids remove passive films mechanically at impingement angles near 30-45 degrees, so a very corrosion-resistant but soft alloy can lose section thickness faster than a harder alloy with moderate corrosion resistance. The practical approach is to set a design velocity ceiling for each component, add an explicit erosion allowance to thick sections, and select alloys whose hardness and strength suit the local solids loading. Duplex 2205 and super-duplex 2507 perform well in low-chloride, high-erosion positions such as gypsum dewatering, while high-velocity high-chloride positions still require C-276 or Alloy 59 despite the erosion penalty. Nozzle bore geometry, header manifold design and pump discharge configurations influence erosion as much as the alloy, so material selection and hydraulic design must be reviewed together. Our engineering knowledge base covers velocity and erosion-allowance practice in more depth.

Q11: What documentation and standards should accompany FGD alloy deliveries?

International FGD projects typically require EN 10204 3.1 mill test certificates linking each heat number to chemical composition, mechanical test results and corrosion or intergranular test results, plus full traceability from slab to finished component. In addition, purchasers should receive welding procedure qualification records, welder performance qualification records, positive material identification results on receipt, and heat-treatment records where thermal processing was performed. The purchase specification should cite the product standard explicitly - for example ASTM B575 for Ni-Cr-Mo flat products, ASTM B906 for generic flat-rolled requirements, ASTM B625 for Alloy 31 and 904L-class products, ASTM B443 for 625, ASTM B168 for Ni-Cr-Fe grades and ASTM B424 for 825 - together with the grade designation in US UNS, GB, JIS, DIN/EN W.Nr and GOST form where the project crosses jurisdictions. Acceptance criteria for cladding, including minimum clad thickness and bond integrity testing, should be stated in the same document. This level of documentation is routine for a mill supplying international scrubber projects, and it prevents the costly disputes that follow a missing test or an unverified heat.

Conclusion: Choose the Alloy for Each Zone, Then Verify It with Standards

FGD scrubber nickel alloy selection is not a single decision, it is a zone-by-zone matching exercise between the local chemistry, temperature, velocity and crevice geometry of the equipment and the corrosion and mechanical data of a defined alloy. Use C-276, Alloy 59 or Alloy 22 for the chloride-rich wetted zones, absorber sump, spray headers and mist eliminator frames; Alloy 31 or 254 SMO for intermediate chloride and moderate-acid zones; 904L or Alloy 20 where chloride stays below roughly 500 mg/L with controlled pH; duplex 2205 or 2507 for gypsum dewatering and other high-erosion, low-chloride duty; and 625, C-22 or C-276 cladding for duct linings, stacks, reheaters and expansion joints exposed to acid dew point condensate. Confirm every choice against ASTM G48 pitting and crevice data, verify heat treatment against ASTM G28 and G36 where relevant, and require EN 10204 3.1 documentation with heat traceability so that what arrives on site matches what was specified. A mixed, well-justified materials list is both safer and cheaper than a uniform one.

If you need help converting a scrubber zone list into a firm alloy specification, send us the water chemistry envelope, temperature range and component list and our engineers will recommend the minimum and preferred alloy for each item, with the applicable standard and available corrosion test data.

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Shanghai Hangbo Alloy Group Co., Ltd. - China Supplier

Email: sales@hangboalloy.com | WhatsApp (Lisa): +86 13611656360 | www.nickel-alloy.com

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Ni: NI200-N6 | Monel: 400-502, K-500, R-405 | Inconel: 600-740H, X-750, 725 | Incoloy: 800-27-7MO | Hastelloy: C-276-HYBRID-BC1, N | Super Austenitic: 904L-AL-6XN | Chromium-Rich: Alloy 33 | High-Strength Stainless: Nitronic 50/60, PH13-8Mo | Chlorination: Alloy 45 | Nimonic: 75-263 | Haynes: 25-HR-160 | RA: 330/333 | Precision: 1J22-4J45 | High-Strength: 18Ni250-AerMet100 | Heating: Cr20Ni80/60 | Specialty: Alloy 20-602CA

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Request a quote for FGD scrubber alloys: contact our sales team and we will respond with alloy recommendations, applicable standards and a firm offer.