Guides/Comparisons
Stainless steel vs aluminium
stainless-steel-vs-aluminiumStainless steel and Aluminium at a glance
This page compares Stainless steel and Aluminium using only values that carry a source, a test condition and an evidence level. Ranges run across temper, heat treatment and product form, measured at room temperature where the source says so.
- Yield strength: the ranges overlap (Stainless steel 170 to 1,896 MPa; Aluminium 29 to 510 MPa).
- Tensile strength: the ranges overlap (Stainless steel 380 to 2,200 MPa; Aluminium 60 to 572 MPa).
- Density: Stainless steel is higher (Stainless steel 7.6 to 8.1 g/cm³; Aluminium 2.65 to 2.84 g/cm³), about 2.9 times the midpoint of Aluminium.
- Young's modulus: Stainless steel is higher (Stainless steel 174 to 220 GPa; Aluminium 57.2 to 79 GPa), about 2.9 times the midpoint of Aluminium.
- Thermal conductivity: Aluminium is higher (Stainless steel 12 to 30 W/(m·K); Aluminium 120 to 229 W/(m·K)), about 8.3 times the midpoint of Stainless steel.
- Melting point: Stainless steel is higher (Stainless steel 1,300 to 1,532 °C; Aluminium 490 to 660 °C), about 2.5 times the midpoint of Aluminium.
- Service temperature: Stainless steel is higher (Stainless steel 232 to 1,100 °C; Aluminium 65 to 160 °C), about 5.9 times the midpoint of Aluminium.
- Thermal expansion: Aluminium is higher (Stainless steel 9.9 to 20.5 ppm/K; Aluminium 21.4 to 25 ppm/K), about 1.5 times the midpoint of Stainless steel.
- Yield strength for each unit of density (calculated from each grade's midpoint values): Stainless steel 23.8 to 248 MPa per g/cm³; Aluminium 10.7 to 180 MPa per g/cm³.
"Higher" means the whole range is higher, not just one value. Where a value is a specified minimum, the table says "at least".
Side by side
| Property | Stainless steel | Aluminium |
|---|---|---|
| Yield strength | 170 to 1,896 MPa | 29 to 510 MPa |
| Tensile strength | 380 to 2,200 MPa | 60 to 572 MPa |
| Density | 7.6 to 8.1 g/cm³ | 2.65 to 2.84 g/cm³ |
| Young's modulus | 174 to 220 GPa | 57.2 to 79 GPa |
| Thermal conductivity | 12 to 30 W/(m·K) | 120 to 229 W/(m·K) |
| Melting point | 1,300 to 1,532 °C | 490 to 660 °C |
| Service temperature | 232 to 1,100 °C | 65 to 160 °C |
| Thermal expansion | 9.9 to 20.5 ppm/K | 21.4 to 25 ppm/K |
| Yield strength per densitycalculated | 23.8 to 248 MPa per g/cm³ | 10.7 to 180 MPa per g/cm³ |
When to use which
| Material | Best for | Weakest at |
|---|---|---|
| Stainless steel 304 | Corrosion-resistant housings, fasteners and tanks where ordinary steel would rust | Chloride pitting in acidic solutions, and low strength compared with precipitation-hardened steels |
| Stainless steel 316 | Chloride-bearing and marine-grade service where 304 would pit, in annealed sheet, bar and plate | Crevice and pitting attack in seawater condenser tubes, intergranular attack after heating between 500 and 900 C, and modest strength next to precipitation-hardened grades |
| Stainless steel 316L | Welded parts in chloride or marine service, and vacuum hardware that is vacuum-fired | Long holds near 650 C form sigma phase, and seawater service needs a pitting resistance equivalent number greater than 40 (Wikipedia) |
| Duplex stainless steel 2205 | Chloride-bearing and sour service where 300-series steels crack, in welded pipe, tube, sheet and plate (ATI, Alleima) | Extended exposure at 343 to 530 C (475 C embrittlement), welds made with straight chromium filler, and sour service above 232 C (ATI, Alleima) |
| Super duplex stainless steel 2507 | Chloride-bearing seawater, subsea and sour oil and gas service that needs high strength and pitting resistance, in solution-annealed tube, bar and forgings | Prolonged exposure above 250 °C, which lowers impact strength, and hydrogen-induced cracking in cathodically protected subsea steel |
| 17-4 PH stainless steel | High-strength fittings, fasteners, shafts and valve parts that need more strength than 304 and moderate corrosion resistance | Stress corrosion cracking and pitting in peak-aged (H900) material, and crevice corrosion in stagnant salt water |
| Stainless steel 440C | Bearings and valve parts that must be hard and wear-resistant in the hardened and tempered condition (Carpenter, Aalco, Rolled Alloys) | Corrosion resistance in the annealed state or after tempering above about 800 F (427 C), and service above about 400 C (NASA 2018 maximum use temperature) |
| Stainless steel 410 | Hardened and tempered valve, shaft and fastener parts that need strength and a magnetic response | Chloride, marine and strong-acid service, and toughness after tempering at 482 to 538 C |
| Stainless steel 430 | Sinks, appliance trim and architectural cladding, where economy and moderate corrosion resistance matter more than strength (ATI) | Welds and sea water. Welds lose ductility and corrosion resistance, and the datasheet says the grade is not resistant to sea water (Deutsche Edelstahlwerke) |
| Martensitic stainless steel 13Cr-4Ni (UNS S41500) | Quenched and tempered turbine, pump and valve parts that need good strength and low-temperature toughness, in low-chloride media with polished surfaces | Chloride pitting (DEW: slight attack with a risk of pitting in saturated NaCl at 20 C), the 23 HRC cap for sour gas, and poor weldability (DEW) |
| Stainless steel 301 | Springs, clips and light formed structures where cold-work strength matters more than corrosion resistance | Chloride pitting (critical pitting temperature below 10 C in Outokumpu's test) and carbide precipitation after welding or holding at 427 to 816 C |
| Stainless steel 303 | Heavily machined parts in mild service, such as screws, nuts, bolts, shafts and fittings (Aalco, UPMET) | Chloride and marine service, where Aalco says 303 is not suitable, and welded joints, where Aalco says weldability is poor |
| Lean duplex stainless steel 2304 | Chloride-bearing process piping and heat exchangers, pulp and paper equipment, and strength-limited structures where 304 or 316 would crack or be too weak (Alleima, ATI) | Exposure above about 315 C (600 F), where 475 C embrittlement can follow (ATI); prolonged exposure above 280 C (Alleima); weld metal without an overmatched filler (ATI) |
| Stainless steel 409 | Automotive exhaust systems and heat exchangers, where corrosion protection is needed beyond carbon steel (Combined Metals) | Pitting and intergranular corrosion: Outokumpu prints a critical pitting temperature below 10 °C and N/N for intergranular corrosion, and Aalco limits welded sheet to about 2.5 mm thick |
| Stainless steel 444 | Hot water tanks, heat exchangers and solar tanks in chloride-bearing water, where resistance to chloride stress cracking matters (ATI, Ugitech, Aperam) | Boiling 10 percent sulphuric and sulfamic acids, where ATI's table shows corrosion above 1000 mils per year, and toughness at transition temperatures, welds included (Aperam) |
| AISI 302 stainless steel | Springs, washers, screens and wire parts that need an 18-8 stainless steel with more carbon than 304 for strength, while keeping ductility (Elgiloy datasheet) | Strength in the annealed state (about 290 MPa typical yield), and ductility after heavy cold work (elongation falls from 48 % at 0 % cold work to 2.2 % at 80 % cold work, fwmetals table) |
| Stainless steel 304L | Welded parts in corrosive service, where the as-welded condition must resist carbide precipitation | Sea water and chloride service: Carpenter rates 304 and 304L restricted in sea water, and no pitting number for 304L was found |
| Stainless steel 310S | Furnace and heat-treatment parts that run hot in oxidising air up to about 1,050 °C, with good creep strength and oxidation resistance | Sulphur-bearing hot gases, which cut the service limit to 950 °C, and long exposure between 650 and 900 °C, which causes sigma-phase embrittlement and chromium-carbide sensitisation |
| AISI 317L stainless steel | Chloride pitting resistance in process equipment, with a low-carbon grade that limits sensitization in welds | Strength in the annealed state (205 MPa minimum yield) and chloride stress cracking above about 49 °C |
| AISI 321 stainless steel | Welded parts that run hot in oxidising air, from 427 to 850 degC: titanium holds the grade against carbide precipitation in the 800 to 1500 degF range | Strength when annealed (about 241 MPa typical yield) and cold-work strength only, plus exposure of 900 to 1500 degF for long periods, which lowers general corrosion resistance |
| AISI 347 stainless steel | Welded hot-service parts that cannot be re-annealed afterwards: niobium stabilisation resists intergranular attack, and the grade is rated to 800 °C in air | Strength when hot: tensile strength falls from 93.3 ksi at 68 °F to 69.5 ksi at 800 °F (Rolled Alloys), and no vacuum, radiation or atomic-oxygen data were found |
| AISI 347H stainless steel | Welded parts for hot service in air and steam, where creep strength to 1500 degF is needed and niobium stabilisation resists intergranular attack in the as-welded condition | Strength when hot: typical tensile strength falls from 93.3 ksi at 68 degF to 69.5 ksi at 800 degF (Rolled Alloys), and no vacuum, radiation or atomic-oxygen data were found |
| Super-austenitic stainless steel 904L | Sulfuric and phosphoric acid plant, seawater condensers and heat exchangers, and pulp bleaching, in annealed sheet, plate, strip and tube, where 316L or 317L would corrode | Halide-containing acids and boiling magnesium or lithium chloride, where ATI's U-bend test cracked the alloy, and crevices in chloride water (ATI G-48 onset at 18 °C) |
| Nitronic 60 stainless steel | Fasteners, pins, bushings and valve trim that must resist galling and wear while staying austenitic and low in magnetic permeability | General corrosion resistance falls between Types 304 and 316, the alloy is hard to machine, the high-strength bar cannot be hot worked or welded without losing strength, and the sources print no space-environment data |
| Lean duplex stainless steel 2101 (UNS S32101) | Chloride-bearing process equipment where a 300 series grade is too weak or too prone to chloride stress cracking, and nickel cost matters: the grade gives about double the 0.2 % yield of 304 and 316 and no SCC in the boiling CaCl2 U-bend test | Use above about 300 °C: Atlas says held above 300 °C the grade embrittles and only a full solution anneal restores it, and no space-environment data (radiation, outgassing, cryogenic toughness) were found |
| Stainless steel 430F | Machined parts cut from bar on automatic screw machines, where machinability matters more than corrosion resistance or weldability (Atlas, Deutsche Edelstahlwerke) | Corrosion and welding. The sulphur addition reduces corrosion resistance, especially pitting and crevice attack, and weldability is poor (Deutsche Edelstahlwerke) |
| Stainless steel 410S | Ferromagnetic, weldable stainless parts for hot or mildly corrosive service, such as distillation trays, tower packing and exhaust components, where the 410 hardening response is not wanted | Chloride and marine service (no 410S test data was found), and room-temperature brittleness in thick sections (Jacquet) |
| AISI 416 stainless steel | Shafts, axles, gears, valve and pump parts and screw-machine parts that must be cut quickly and then hardened, kept away from chloride exposure | Corrosion resistance. The sulfur addition lowers it below the non-free-machining grade 410, and the Aalco datasheet calls high-sulfur free-machining grades totally unsuitable for marine or chloride exposure |
| Stainless steel 420 | Hardened wear parts, blades and bearing-type components that need high strength and edge retention, from one steel that reaches 48 HRC after tempering at 440 °F | Corrosion resistance and ductility: it resists corrosion less well than austenitic grades, and it loses strength when tempered at 1000 °F (158.5 ksi tensile) |
| Stainless steel 431 | High tensile and torsional strength in shafts, valve stems and pump parts that also need reasonable corrosion resistance (Smith Metal, Smiths High Performance) | Welding and cold forming: welds crack unless preheated, and the grade is not recommended for cold heading or bending (Smiths High Performance, Voestalpine) |
| Martensitic stainless steel | Quenched and tempered shafts, axles and pump parts that need strength, toughness and good general corrosion resistance, with limited marine exposure (DEW) | Chloride pitting: DEW gives a risk of pitting corrosion in saturated sodium chloride and in sea water at 20 C, and welds need heat treatment afterwards (DEW) |
| 17-7 PH stainless steel | Springs, Belleville washers, eyelets and flat springs that need high strength and stainless corrosion resistance, with formability in the soft state | Stress corrosion cracking in chloride and in nitrogen tetroxide/hydrazine propellant, in every heat-treated condition except CH 900; ductility in CH 900 (2 % elongation) |
| PH 15-7 Mo stainless steel (15-7 PH) | Springs, retaining rings and seal rings that need high strength with a low-distortion hardening heat treatment (ATI and Ulbrich list these uses) | Stress corrosion cracking in salt water: the 1969 NASA test found the alloy cracked in all conditions except CH 900, and corrosion resistance is below Type 304 (ATI) |
| Aluminium alloy 6061 | A light, workable structural metal with good corrosion resistance (the NASA handbook ranks 6061 best of the heat-treatable aluminium alloys for corrosion) | Galvanic attack when coupled to more noble metals, especially in sea water (NASA handbook); typical strength values are marked not for design |
| Aluminium alloy 7075-T6 | High-strength aluminium parts where low mass and wrought forms such as tube, plate, bar or forging are useful | Stress-corrosion cracking in the short-transverse direction in T6, and relatively poor corrosion resistance in industrial and marine environments |
| Aluminium alloy 2024 | A high-strength wrought aluminium alloy for aircraft fittings and structural parts (the datasheets list these uses; ASM typical T4 yield strength is 324 MPa) | Stress-corrosion cracking of the 2024-T351 temper in seacoast and salt-water conditions (NASA 1981), and pitting in salt water |
| Aluminium alloy 5052 | Welded sheet and tank or marine-style parts at medium strength, where the temper is named and checked (the datasheets rate its seawater resistance very good) | Strength depends on temper (yield 13 ksi annealed to 37 ksi in H38), and no measured seawater corrosion rate was found in the sources read |
| Aluminium-magnesium alloys (5XXX series) | Welded, corrosion-resistant sheet and plate at moderate strength (5083 is sold for ship building and pressure vessels) | Strength per alloy is modest next to heat-treated 6061, and 5083 is not recommended above 65 °C because of grain-boundary attack |
| Aluminium-lithium alloy 2195 | Welded cryogenic tanks where friction stir welding keeps most of the strength (NASA reports, 1998 to 2008) | Fusion welding, which hot-cracks and needs repairs, and corrosion resistance, which the supplier calls poor |
| Aluminium | Light, cheap electrical and thermal conduction, and a positive-electrode foil that stays passive in common lithium-ion electrolytes | Strength: annealed pure aluminium has a typical yield strength near 22 to 29 MPa, so it is not a structural metal on its own |
| Aluminium alloy 1050 | Formed sheet, chemical plant and heat-transfer parts that need very good corrosion resistance and easy forming more than strength (Smiths and Righton list these uses) | Low strength in the soft tempers (Smiths gives 100 to 135 N/mm2 typical tensile for 1050A H14, and 1200 O is 70 to 105 N/mm2); no measured corrosion test data were read |
| Aluminium alloy 2011 | Small, complex, high-precision machined parts made on automatic lathes, such as screws, bolts, gears, fasteners and fittings (suppliers rate machinability very good to excellent) | Weldability (rated poor to extremely poor by the sources) and corrosion resistance (rated low to moderate, and anodising or another surface treatment is advised) |
| Aluminium alloy 2014 | High-strength structural parts for aerospace and defence, where a 460 MPa minimum tensile strength in T651 plate is needed and the part is clad or painted against corrosion | Corrosion resistance (poor in water and salt, with pitting and galvanic attack in sea water), and welding, which is difficult and prone to cracking |
| Aluminium alloy 2017 | High-strength machined parts and rivets in aircraft-type structures, in the T4 temper (supplier rates machinability excellent, strength very good) | Weldability (only resistance welding is suitable, per the AircraftMaterials datasheet) and corrosion resistance (rated moderate by the supplier, with no test data found for this grade) |
| Aluminium alloy 2017A | Machined structural parts and solid rivets in the T4 temper (supplier rates machinability Excellent, yield strength 276 MPa) | Welding (resistance welding only, per the Smith and AircraftMaterials datasheets) and corrosion resistance (rated moderate by one supplier and good by another, with no test data for this grade) |
| Aluminium alloy 2219 | Launch-vehicle and cryogenic tankage where weldability and fracture toughness matter (Smith datasheet: readily weldable, good fracture toughness; Alloys International: launch vehicle and cryogenic tanks) | Ductility in thick plate, where 5-inch T87 plate showed below 1 % in the short-transverse direction (NASA 2021), and general corrosion resistance, which Wikipedia describes as lower than other aluminium alloys |
| Aluminium alloy 3003 | Sheet and formed parts that need moderate strength, good workability and weldability, and resistance to atmospheric corrosion, such as storage tanks, chemical equipment and heat exchangers, with the temper named | Strength depends on temper, from 14 to 19 ksi tensile in O to 27 ksi minimum in H18, and no seawater rating or measured corrosion rate for 3003 was found in the sources read |
| Aluminium alloy 5083 | Welded marine structures and pressure vessels kept at or below 65 °C, where seawater resistance and strength matter (supplier datasheets) | Service above 65 °C, where the suppliers advise against use. It is a non-heat-treatable alloy (Dinco sheet). No space-environment data were found. |
| Aluminium alloy 5251 (AlMg2) | Welded marine and sheet-metal structures where seawater corrosion resistance and weldability matter more than peak strength, at 2.69 g/cm3 | Strength compared with heat-treatable alloys: H22 minimum proof stress is 120 MPa, and a good weld reaches only about 160 MPa (Smith) |
| Aluminium alloy 5754 (AlMg3) | Welded structures and marine or chemical service where seawater corrosion resistance matters, at a density of about 2.67 g/cm3 | Strength against heat-treatable aluminium alloys, since strength comes from the temper, and the risk of sensitisation in magnesium-rich grades held warm for long periods (no temperature threshold for this grade was verified) |
| Aluminium alloy 6013 | Light structural aluminium for aerospace and general structural use: 2.71 g/cm3 density, and 350 MPa yield in the T651 temper (supplier page) | Dust and chips ignite readily during machining (Hydro SDS). No fatigue, fracture-toughness or T6 temper data was opened, and the sources disagree on thermal expansion |
| Aluminium alloy 6063 | Architectural extrusions such as window and door frames, rails and trim that need a smooth anodised finish (Alloys International; AZoM). | Strength: Alloys International says 6061 is the higher-strength choice for structural parts, and no space-environment, cryogenic or galvanic data were found for 6063. |
| Aluminium alloy 6082 | Structural parts that must be strong but light: T6 and T651 plate with minimum proof stress 255 MPa and density 2.70 g/cm3 | Strength in the weld zone, which the supplier says is lowered by welding, and pitting or intergranular attack in chloride solution (lab immersion test at 50 °C) |
| Aluminium alloy 7050 (AA7050) | Thick, high-strength aerospace structure in the over-aged T74 or T7451 conditions, where high yield strength and good exfoliation resistance are needed | Weld zones: friction-stir welds of 7050-T7451 showed less cracking resistance than 7075-T651 welds in constant extension rate tests (2003 study) |
| Aluminium alloy 8011 (AA8011) | Thin, light foil and fin stock: 2.71 g/cm3 density with 210 to 220 W/(m·K) thermal conductivity in H19 foil at 20 °C | Yield strength and corrosion data are missing from this profile, and no spacecraft use was found in any source read |
Where each is used
| Material | Use |
|---|---|
| Stainless steel 304 | Spacecraft propellant tank |
| Stainless steel 304 | Fasteners and screws |
| Stainless steel 304 | Architectural cladding |
| Stainless steel 316 | Aerospace structures |
| Stainless steel 316 | Chemical storage, food processing and oil refining equipment |
| Aluminium alloy 6061 | Launch vehicle and spacecraft structures (aluminium alloys, 6061 named as a structural alloy) |
| Aluminium alloy 6061 | Simulated propellant tanks of 6061-T3 sheet (ground impact tests, not flown) |
| Aluminium alloy 6061 | Fittings, couplings, hinge pins, valves and valve parts, and hydraulic and brake pistons |
| Aluminium alloy 7075-T6 | Aircraft structures and airframe parts |
| Aluminium alloy 7075-T6 | High-pressure hydraulic units |