Alloy 28，Incoloy 028 Pipe，UNS N08028

British Specs:，American Specs:，German Specs:WS 1.4563

Alloy 28 (Incoloy 028 Wire, UNS N08028) - Introduction with Composition, Properties, Applications and Product Forms

Alloy 28, commercially known as Incoloy 028 and designated by UNS N08028, is a nickel-iron-chromium-molybdenum alloy renowned for its exceptional resistance to sulfuric acid and other aggressive corrosive environments, along with good mechanical strength and excellent weldability. This high-performance alloy is specifically engineered to thrive in both reducing and oxidizing conditions, making it a preferred choice for chemical processing and industrial applications involving harsh chemicals. It is available in a comprehensive range of forms to meet diverse industrial needs, including Bar (Round bar, Flat bar), Ribbon, Wire, Rods, Tube, Pipe, Foil, Plate, Sheet, Strip, and Forging Stock. Incoloy 028 Wire, in particular, is valued for its flexibility, corrosion resistance, and precision, making it ideal for intricate components in chemical processing, marine, and pollution control industries. Below is a detailed overview of its chemical composition, key properties, practical applications, and available product forms.

Chemical Composition

The precisely balanced chemical composition of Alloy 28 (Incoloy 028, UNS N08028) is the foundation of its exceptional corrosion resistance and mechanical performance. The typical composition (by weight) is as follows:

Nickel (Ni): 30-34% (primary matrix element, providing corrosion resistance and structural stability)

Iron (Fe): 39-47% (enhances mechanical strength and fabricability)

Chromium (Cr): 19-21% (critical for oxidation resistance, forming a protective chromium oxide layer in oxidizing environments)

Molybdenum (Mo): 3.0-4.0% (boosts resistance to pitting, crevice corrosion, and reducing acids such as sulfuric acid)

Carbon (C): ≤ 0.03% (controlled to minimize carbide precipitation, preserving corrosion resistance)

Manganese (Mn): ≤ 2.0% (aids in deoxidation during manufacturing and improves weldability)

Silicon (Si): ≤ 1.0% (assists in forming a stable oxide layer, enhancing oxidation resistance)

Copper (Cu): ≤ 0.75% (improves resistance to sulfuric acid and other reducing acids)

Sulfur (S): ≤ 0.03% (kept at low levels to ensure good ductility and weldability)

Phosphorus (P): ≤ 0.03% (controlled to maintain corrosion resistance and avoid embrittlement)

This carefully engineered composition, with its high nickel, chromium, and molybdenum content, delivers the alloy's signature resistance to sulfuric acid, pitting corrosion, and general chemical attack, making it suitable for the most demanding corrosive industrial environments.

Key Properties

Alloy 28 (Incoloy 028 Wire, UNS N08028) and its various forms exhibit a robust set of properties that make them indispensable in corrosive, high-temperature, and high-stress applications:

Mechanical Properties (room temperature, annealed condition):

Tensile strength: 550-690 MPa (79,800-100,100 psi)

Yield strength (0.2% offset): 240-310 MPa (34,800-44,900 psi)

Elongation (in 50 mm): 30-45% (excellent ductility, enabling complex forming, bending, and welding across all product forms)

Hardness: 150-190 HB (Brinell hardness, indicating good machinability and workability)

High-Temperature Performance:

Thermal stability: Maintains significant strength up to 650°C (1202°F), with tensile strength remaining above 300 MPa at 500°C (932°F)

Creep resistance: Exhibits good creep resistance at 400-600°C (752-1112°F), suitable for long-term service under sustained stress in moderate high-temperature systems

Oxidation resistance: Resistant to oxidation in air and combustion gases up to 800°C (1472°F), forming a dense, self-healing chromium oxide layer

Thermal fatigue resistance: Good resistance to thermal cycling, making it suitable for applications with moderate temperature fluctuations

Corrosion Resistance:

Sulfuric acid resistance: Exceptional resistance to sulfuric acid across a wide range of concentrations and temperatures, a key advantage over many other alloys

General corrosion resistance: Excellent resistance to both oxidizing and reducing acids, including hydrochloric acid (dilute), phosphoric acid, and organic acids

Chloride resistance: Superior resistance to pitting and crevice corrosion in chloride-rich environments, including seawater, brines, and industrial effluents

Wet corrosion: Resistant to alkaline solutions, industrial chemicals, and polluted water, ensuring versatility across diverse industries

Stress corrosion cracking (SCC): Highly resistant to SCC in sulfuric acid and chloride-containing environments, even at elevated temperatures

Physical Properties:

Density: 8.0 g/cm³ (0.289 lb/in³)

Thermal conductivity: 15.0 W/(m·K) at 20°C (68°F), increasing to 22.0 W/(m·K) at 650°C (1202°F)

Melting point: 1350-1400°C (2462-2552°F)

Coefficient of thermal expansion: 16.0 μm/(m·K) (20-100°C), rising to 19.0 μm/(m·K) at 650°C (1202°F)

Modulus of elasticity: 200 GPa (29,000 ksi) at room temperature, decreasing to 160 GPa (23,200 ksi) at 650°C (1202°F)

Product Forms

Alloy 28 (Incoloy 028, UNS N08028) is manufactured in a diverse range of forms to accommodate specialized industrial processes across chemical, marine, and pollution control sectors:

Bar: Available as Round bar (diameters from 8 mm to 300 mm) and Flat bar (thickness 6 mm to 150 mm, width 20 mm to 600 mm), ideal for machining into valve components, pump shafts, and chemical processing hardware.

Ribbon: Thin, flat strips (thickness 0.1 mm to 2 mm, width 5 mm to 100 mm) used in electrical contacts, gaskets, and seals for corrosive equipment.

Wire: Incoloy 028 Wire (diameters 0.05 mm to 10 mm) offers excellent flexibility and corrosion resistance, making it suitable for thermocouple leads, sensor wiring, woven mesh filters, and precision springs in aggressive chemical environments.

Rods: Solid cylindrical rods (diameters 3 mm to 50 mm) suitable for structural supports in chemical reactors, marine equipment, and pollution control systems.

Tube and Pipe: Seamless and welded options (outer diameter 6 mm to 200 mm, wall thickness 0.5 mm to 20 mm) for transporting corrosive fluids, including sulfuric acid, hydrochloric acid, and industrial chemicals, in processing systems.

Foil: Ultra-thin sheets (thickness 0.01 mm to 0.1 mm) used in lightweight corrosion barriers, liners for precision chemical instruments, and electrical components.

Plate and Sheet: Flat forms (plate: thickness 5 mm to 100 mm; sheet: 0.3 mm to 5 mm) for fabricating reactor vessel liners, storage tanks, heat exchanger panels, and marine structural parts.

Strip: Narrow, flat strips (thickness 0.1 mm to 3 mm, width 10 mm to 200 mm) for precision manufacturing in gaskets, clips, and electrical components for corrosive systems.

Forging Stock: Billets and ingots for hot forging into complex shapes such as pump impellers, valve bodies, and marine hardware.

Applications

The exceptional corrosion resistance properties of Alloy 28 (Incoloy 028 Wire, UNS N08028) across its various forms make it a critical material in industries requiring performance in aggressive chemical environments:

Chemical Processing:

Sulfuric acid production and handling: Tanks, pipes, and valves (from plate, tube, and bar) for processing and transporting sulfuric acid across a wide range of concentrations and temperatures.

Acid recycling systems: Components for recovering and reprocessing spent acids, including heat exchangers (from tube and sheet) and filter housings (from plate).

Fine chemical manufacturing: Reaction vessels (from plate), transfer lines (from tube), and agitators (from bar) for producing pharmaceuticals, dyes, and specialty chemicals.

Marine and Offshore:

Seawater processing: Desalination plants, seawater cooling systems, and offshore drilling equipment (from plate, tube, and bar) resisting saltwater corrosion.

Marine construction: Hull components, propeller shafts, and seawater intake systems (from plate, sheet, and forging stock) for ships and offshore platforms.

Offshore oil and gas: Piping systems (from tube) for produced water handling, chemical injection lines, and corrosion-resistant structural supports (from rod).

Pollution Control:

Flue gas desulfurization (FGD) systems: Components for removing sulfur dioxide from power plant emissions, including scrubber vessels (from plate), spray nozzles (from forging stock), and ducting (from sheet).

Wastewater treatment: Equipment for processing industrial wastewater, including clarifiers (from plate), sludge handling systems (from bar), and chemical dosing lines (from tube).

Air pollution control: Filters and scrubbers (from wire mesh and sheet) for removing corrosive pollutants from industrial exhaust gases.

Metallurgical Processing:

Acid leaching: Equipment for extracting metals from ores using acids, including leach tanks (from plate) and agitators (from bar).

Electroplating: Tanks, racks, and anode/cathode supports (from sheet, wire, and bar) resisting plating bath chemicals.

Pickling lines: Components for removing oxide scales from metals, including rollers (from bar) and bath liners (from sheet).

Specialized Applications by Form:

Wire: Thermocouple leads in chemical reactors, sensor wiring in corrosive environments, and woven mesh filters for acid filtration.

Tube/Pipe: Chemical transport lines, heat exchanger tubes in acid processing, and sampling lines for aggressive fluids.

Plate/Sheet: Reactor vessel liners, storage tank walls, and marine structural panels resistant to both corrosion and moderate temperatures.

Bar/Forging Stock: Machined valves, pump shafts, and marine hardware requiring high strength and corrosion resistance.

In summary, Alloy 28 (Incoloy 028 Wire, UNS N08028) — available in forms from Bar and Wire to Plate and Forging Stock — delivers exceptional resistance to sulfuric acid and other aggressive chemicals, along with good mechanical strength and formability. Its diverse product forms enable tailored solutions across chemical processing, marine, and pollution control sectors, establishing it as a critical material in the most demanding corrosive industrial applications.

Packing of Standard Packing: 

Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and steel drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 2693 gallon liquid totes Special package is available on request.