Aluminum vs Stainless Steel: Weight, Strength, Cost and Laser Cutting (2026)

Aluminum is about one third the weight of stainless steel, and roughly 45% cheaper per square metre at the same thickness, even though it costs more per tonne. Stainless steel wins on strength, high temperature service and hygiene. On the same fiber laser, stainless cuts about twice as fast. Pick aluminum when weight and finished cost drive the job. Pick stainless when the part carries load, runs hot, or has to stay clean.

I quote both materials every week for window fabricators, solar bracket makers and food equipment builders. Nine times out of ten the argument comes down to five numbers: density, yield strength, price per tonne, price per square metre, and cutting speed.

Here is the aluminum vs stainless steel comparison, using September 2026 prices out of China.

Aluminum vs Stainless Steel at a Glance

Weight Is Where Aluminum Wins by a Mile

Aluminum sits at 2.70 g/cm³. Stainless steel sits at 7.93 g/cm³. That is not a small difference — stainless is 2.9 times heavier for the same volume.

Put it on a real sheet. One square metre of 3 mm aluminum weighs 8.1 kg. The same square metre in 304 stainless weighs 23.8 kg. You are moving almost 16 kg less for every panel.

On a curtain wall job this changes the whole delivery. Panels come off the truck lighter, installers handle them with two men instead of four, and the support framing carries a fraction of the load. Same story on solar mounting: the racking holds the panel weight, so lighter sheet means less steel in the structure underneath.

Stainless has one reverse advantage. Its higher stiffness means a thin gauge stays flatter and resists oil-canning better. When a customer wants a 1 mm panel that stays dead flat, stainless often does the job that would need 2 mm aluminum.

Strength: Stainless Wins Flat Out, Aluminum Wins Per Kilo

In absolute terms stainless is the stronger material. 304 has a 515 MPa tensile strength against 310 MPa for 6061-T6. Yield is closer at the low end — 304 at 205 MPa against 5052-H32 at 193 MPa — but the heat treated aluminum grades pull away: 7075-T6 reaches 503 MPa yield, which beats 304.

The more useful number for a mobile part is strength per kilo. Here aluminum takes it back. 7075-T6 runs about 200 kN·m/kg of specific strength. 304 stainless runs about 65 kN·m/kg. Aluminum gives you roughly three times the load per kilogram.

Two practical notes from quoting this daily. First, aluminum loses strength fast when it gets hot — 6061-T6 starts dropping above about 150 °C, and stainless holds its properties well past 500 °C. Second, aluminum plate over 25 mm is usually not the same alloy through the thickness after quenching. If you are machining a stressed part from thick aluminum, ask for 6061-T651 stress relieved plate. Our aluminum alloy plate range covers 1050 through 7075 with the tempers listed per grade.

Price Per Tonne Versus Price Per Square Metre

This is the part that trips most buyers up. Aluminum is the more expensive metal by weight right now, not the cheaper one.

Run the arithmetic and aluminum is 44% cheaper per square metre at the same thickness. Same panel size, same thickness, near half the material bill.

LME aluminum 3-month was $3,434/t in mid September 2026, with 6063 extrusion FOB China at $3,784/t. The LME moves the aluminum number. Nickel moves the stainless number, and nickel has been the calmer of the two this year, which is exactly why 304 looks cheap per tonne against aluminum right now.

Do not stop the comparison at material. Aluminum is also the cheaper metal to fabricate. It machines two to four times faster than stainless, cuts with less power, and needs no pickling after welding. Stainless eats tooling and consumables. By the time a part is finished the gap is usually wider than 44%, not narrower.

One thing to watch. Aluminum prices are quoted against a Shanghai or LME base plus a conversion premium, so a 5% LME move changes your quote. If you are budgeting a long project with aluminum, ask for a validity window in writing. See the worked examples in our aluminum sheet weight and price per kg guide.

Corrosion: Two Different Mechanisms, Two Different Failure Modes

Both materials resist rust, but not the same way, and they fail in different places.

Aluminum protects itself with a thin oxide film that re-forms within seconds of being scratched. In normal atmosphere, fresh water and most construction exposure it holds up for decades. Chloride is the weak point — salt spray and coastal air break the film down. That is why 5052 and 5083 exist: the magnesium content in the 5xxx series is what gives aluminum its real marine performance. Our stainless steel range and the aluminum 5xxx grades are the two materials I quote most for coastal projects.

Stainless relies on chromium. 304 carries 18% chromium and 8% nickel, and the passive layer needs oxygen to rebuild. That is why 304 fails in crevices and under deposits where oxygen cannot reach. In coastal or chloride-heavy service, 316L with 2–3% molybdenum is the correct grade, not a luxury upgrade.

One failure mode is worth flagging because it is avoidable. Never bolt aluminum directly to stainless steel in a wet environment. The galvanic potential gap is large, aluminum becomes the anode, and it will corrode at the joint fast. Use an isolating washer, a coated fastener, or a rubber gasket.

Laser Cutting: Stainless Runs About Twice as Fast

On a fiber laser, stainless steel cuts faster than aluminum at every thickness. The gap widens as the sheet gets thicker.

Reference parameters on a 1.5 kW fiber laser with nitrogen assist gas:

Same comparison on a 3 kW source, still nitrogen:

At 1 mm the two materials are close. By 6 mm aluminum is running at under a quarter of the stainless speed. If your shop cuts both, that single line changes how you quote a mixed order.

Why Aluminum Cuts Slower

Three reasons, and you can feel all of them on the machine.

First, reflectivity. Bare aluminum throws back close to 90% of a 1,064 nm fiber laser beam at room temperature. Stainless reflects closer to 60%. Less energy absorbed means you have to feed more power or slow the head down.

Second, the oxide layer. Aluminum oxide melts at about 2,072 °C while the aluminum underneath melts at 660 °C. You are cutting through a ceramic skin before you reach the metal, which is why the pierce takes longer and the kerf is less predictable.

Third, heat conduction. Aluminum conducts heat at 167 W/m·K against 16.2 W/m·K for 304 stainless — about ten times faster. The heat you put in leaks sideways instead of cutting, so more of your power goes into warming the sheet.

Practical settings for aluminum: nitrogen at higher pressure than you would use on stainless, a slightly larger nozzle, and a focus position set a little deeper into the material. If you want the parameters we ship with our machines, they are listed on the fiber laser cutting machine page.

Laser Welding: Stainless Is Easier, Aluminum Needs Care

Stainless is the friendlier material to laser weld. It conducts heat slowly, holds a stable keyhole, and gives you a clean bead with argon or nitrogen shielding. 304 and 316L both weld well on a handheld or fiber laser welder.

Aluminum is more work, and the reason is porosity. Molten aluminum dissolves a lot of hydrogen, and once it freezes the solubility collapses. Any moisture or oil on the surface or the filler becomes gas pockets in the weld. Wipe the joint with acetone, keep the filler dry, and use argon or an argon-helium mix.

Not every aluminum grade welds. The 5xxx and 6xxx series weld fine. The 2xxx and 7xxx series are heat treatable and prone to cracking, so most shops avoid fusion welding them. If you are building a welded aluminum assembly, specify 5052, 5083 or 6061 from the start.

Power is the other difference. Expect to run roughly 20–30% more power on aluminum than on stainless of the same thickness, for the same reflectivity reason. A 1.5 kW handheld handles 3 mm aluminum comfortably; 6 mm aluminum is where a 3 kW source starts to earn its price. Details are on the laser welding machine page.

Which One for Your Job

Choose aluminum when:

• Weight matters — transport parts, solar mounting, aerospace, signage, lift equipment
• You want heat to move — heat sinks, LED housings, battery cooling plates
• Cost per square metre is the deciding number at the thickness you are buying
• The part forms or machines a lot — aluminum cuts and shapes much faster
• Architectural work outdoors, with anodizing or powder coating for finish

Choose stainless steel when:

• The part carries structural load or takes impact
• Service temperature goes above 150 °C
• Food, dairy, pharma or chemical contact — cleanable, non-porous, and it will not pit in normal washdown
• You need a thin panel that stays flat, or a stiff part in a tight envelope
• The environment is chloride-heavy and you can afford 316L

Aluminum vs stainless steel rarely has one clean answer. If you are still on the fence, send me the drawing. I will tell you which material is cheaper for your specific part, including cutting time, and I will not sell you stainless where aluminum does the job.

Send your grade, thickness, size, finish and destination port, and you get a firm price with the loading plan. Request a quote here.

Frequently Asked Questions

Written by David Chen, Sales Engineer at FANY LASER. Connect on LinkedIn for stainless steel and aluminum sourcing, price data and market updates.

Price and parameter sources: Saky Steel China stainless market update, 9 September 2026; Aluminium-China LME and FOB Shanghai benchmarks, September 2026; Henan HC Aluminum sheet FOB data, April 2026; SBMachines fiber laser parameter tables, 2026. Reference parameters are typical values and must be confirmed on your own machine before production.