The first decision in any sheet metal project is material selection. Get it right, and everything downstream — bending, welding, coating, assembly — flows smoothly. Get it wrong, and you’ll fight warpage, corrosion, weld cracks, or cost overruns for the entire production run. At Fulei Metal, we process four primary materials every day. Here’s a practical guide to choosing among them, based on what we’ve learned making parts for customers in 20+ countries since 2016.
The four materials at a glance
| Property | SPCC (Cold-Rolled Steel) | SECC (Electrogalvanized Steel) | SUS304 (Stainless Steel) | Aluminum 5052/6061 |
|---|---|---|---|---|
| Standard | JIS G 3141 | JIS G 3313 | JIS G 4305 / AISI 304 | AA 5052-H32 / AA 6061-T6 |
| Density (g/cm³) | 7.85 | 7.85 | 8.00 | 2.70 |
| Tensile strength (MPa) | 270–350 | 270–350 | 520–750 | 230–310 (5052) |
| Yield strength (MPa) | 175–235 | 175–235 | 205–410 | 150–195 (5052-H32) |
| Corrosion resistance | Poor (needs coating) | Moderate (zinc layer) | Excellent | Excellent (natural oxide) |
| Weldability | Excellent (MIG/TIG/spot) | Good (MIG/spot, fumes from zinc) | Moderate (TIG, needs skill) | Good (TIG/MIG, needs filler) |
| Formability | Excellent | Good (zinc can flake at tight bends) | Moderate (work hardens fast) | Excellent (5052), Fair (6061-T6) |
| Relative cost (1.0 = SPCC) | 1.0 | 1.15 | 3.5–5.0 | 2.5–3.5 |
| Typical application | Indoor enclosures, brackets | Electrical cabinets, appliance parts | Food equipment, medical, outdoor | Lightweight enclosures, heat sinks |
SPCC: the default workhorse
SPCC (Steel Plate Cold Rolled Commercial) per JIS G 3141 is the most common sheet metal material we process. It’s a low-carbon cold-rolled steel — typically 0.08–0.15% carbon — that bends cleanly, welds easily, and takes surface treatments well. If you don’t specify a material, this is what you’re probably getting.
Advantages: SPCC is the cheapest structural sheet metal available. It has excellent formability — it can be bent to tight radii without cracking, and it doesn’t work-harden the way stainless does. It welds beautifully with MIG, TIG, and spot welding. Surface treatments (powder coat, electroplate, galvanize) all bond well after proper pre-treatment.
Limitations: SPCC has zero corrosion resistance on its own. Expose bare SPCC to humidity and it will rust within days. Every SPCC part needs a surface treatment, which adds cost and lead time. It’s also magnetic, which matters if your application requires non-magnetic properties.
When to use SPCC: Indoor applications where the part will be powder coated or electroplated — server racks, indoor electrical enclosures, brackets, chassis frames, appliance housings. It’s the baseline material for cost-driven OEM work.
SECC: pre-coated convenience
SECC (Steel Electrogalvanized Cold Rolled Commercial) per JIS G 3313 is SPCC with a thin zinc layer (typically 5–20 µm) applied by electroplating at the mill. You’re buying steel that’s already corrosion-protected.
Advantages: SECC eliminates the need for a separate plating step after fabrication. For parts that will be powder coated, the zinc layer provides an additional corrosion barrier underneath the paint. It’s paintable directly — the zinc surface accepts powder coat after a light chromate or phosphate conversion. The cost premium over SPCC is modest (10–20%).
Limitations: The zinc layer can flake at tight bend radii — if you bend SECC to an inside radius smaller than 1x thickness, the zinc may crack and peel at the bend. Welding SECC produces zinc fumes (which are a health hazard and require proper ventilation) and the zinc vaporizes in the weld zone, leaving a bare steel area that needs touch-up. The corrosion resistance is moderate — fine for indoor and mild outdoor, but not sufficient for marine or heavy industrial environments.
When to use SECC: Electrical enclosures, computer cases, appliance housings, and any indoor part that needs moderate corrosion protection without a separate plating step. It’s also a good substrate for powder coating when you want a corrosion barrier under the paint but don’t need the cost of galvanizing.
SUS304: when corrosion matters
SUS304 (per JIS G 4305, equivalent to AISI 304 / EN 1.4301) is an austenitic stainless steel containing 18% chromium and 8% nickel. It’s the standard “food-grade” stainless used in everything from kitchen equipment to medical devices.
Advantages: SUS304 has excellent corrosion resistance — it won’t rust in normal atmospheric conditions, resists most chemicals, and is suitable for food contact (FDA-compliant) and medical applications. It has high strength (520–750 MPa tensile) and maintains its properties at elevated temperatures. It’s non-magnetic in the annealed condition. And it looks good — a brushed or polished 304 surface has a premium feel that powder-coated steel can’t match.
Limitations: SUS304 is 3.5–5x the cost of SPCC. It work-hardens rapidly during forming, which means bend tools wear faster and spring-back is more pronounced — we typically add 2–3 degrees of over-bend compared to SPCC. Welding stainless requires TIG with proper filler rod (typically ER308L) and argon back-purging to prevent sugaring on the back side. It’s also thermally less conductive than carbon steel, so heat dissipation in welded areas is slower. Finally, 304 is susceptible to pitting corrosion in chloride environments (coastal areas, swimming pools) — for those, we upgrade to SUS316.
When to use SUS304: Food processing equipment, medical device housings, kitchen appliances, outdoor architectural parts, chemical processing equipment, and any application where corrosion resistance is non-negotiable or the material will be visible without coating.
Aluminum 5052 and 6061: lightweight and corrosion-proof
We process two main aluminum alloys: 5052-H32 and 6061-T6. They behave very differently, and choosing the wrong one is a common mistake.
5052-H32 is a non-heat-treatable alloy with excellent formability. It’s our go-to aluminum for bending — it forms complex shapes without cracking, has good corrosion resistance (better than 6061 in salt water), and welds well with TIG using ER5356 filler. Tensile strength is 230–290 MPa. We use it for enclosures, marine parts, and any formed aluminum component.
6061-T6 is a heat-treatable alloy with higher strength (310 MPa tensile in T6 temper). It’s excellent for structural applications, machined parts, and welded frames. But 6061-T6 has poor formability — it will crack at bend radii tighter than 2x thickness, and tight bends in general are risky. It’s also more susceptible to stress corrosion cracking than 5052. We use 6061 for flat parts, structural brackets, CNC-machined components, and applications where strength matters more than formability.
Advantages of aluminum: Aluminum is about one-third the weight of steel (2.70 vs 7.85 g/cm³), which is significant for weight-sensitive applications. It has excellent natural corrosion resistance — the aluminum oxide layer forms instantly and self-heals. It conducts heat 3–4x better than steel, making it ideal for heat dissipation enclosures. And it’s non-magnetic and non-sparking.
Limitations: Aluminum is 2.5–3.5x the cost of SPCC by weight, and because it’s less dense, you need more volume for the same strength — so the cost premium per part is significant. It’s softer than steel, so it scratches and dents more easily. Welding aluminum requires different techniques (AC TIG or pulsed MIG) and skilled operators. And aluminum has a high coefficient of thermal expansion (23.1 µm/m·K vs 12 for steel), which means it moves more during welding and requires careful fixturing.
When to use aluminum: Weight-sensitive applications (aerospace, automotive, portable equipment), heat dissipation enclosures (electronics, LED lighting), marine environments (5052 specifically), and applications requiring non-magnetic or non-sparking properties.
Weldability comparison
Weldability is often overlooked in material selection, but it has a direct impact on fabrication cost and quality. Here’s how the four materials compare in our welding shop:
- SPCC: Excellent. MIG, TIG, spot — all processes work well. Minimal pre-cleaning. Lowest skill requirement.
- SECC: Good, but zinc fumes require ventilation and respirators. The weld zone loses its zinc coating, so those areas need touch-up plating or paint. Spot welding works well because the zinc is thin.
- SUS304: Moderate. Requires TIG with ER308L filler and argon back-purge. Heat input must be controlled to prevent carbide precipitation (sensitization) in the heat-affected zone, which reduces corrosion resistance. Skilled welder required.
- Aluminum: Good with the right process (AC TIG or pulsed MIG) and skilled operator. Requires thorough cleaning (remove oxide layer) and proper filler selection (ER4043 or ER5356). Fixturing is critical due to thermal expansion.
Formability comparison
How well a material bends and forms affects what geometries are possible and how tight your bend radii can be:
- SPCC: Excellent. Bends cleanly to inside radius = 1x thickness. Minimal spring-back.
- SECC: Good. Similar to SPCC, but zinc may flake at radii tighter than 1.5x thickness. Use larger bend radii for visible surfaces.
- SUS304: Moderate. Work-hardens rapidly — each bend stroke increases hardness in the bend zone. Spring-back is 2–3x that of SPCC, requiring over-bend compensation. Inside radius should be at least 1.5x thickness.
- Aluminum 5052-H32: Excellent. Bends to inside radius = 1x thickness without cracking. Very low spring-back.
- Aluminum 6061-T6: Poor. Cracks at radii tighter than 2x thickness. For bent parts, use 5052 instead, or bend 6061 in T0/T4 temper and heat-treat after forming.
Cost ranking and decision framework
In terms of material cost per kilogram (relative to SPCC = 1.0):
- SPCC — 1.0 (baseline)
- SECC — 1.15
- Aluminum 5052/6061 — 2.5–3.5
- SUS304 — 3.5–5.0
But material cost is only part of the picture. Total part cost includes fabrication, welding, and surface treatment. A bare SPCC part needs coating, which adds $0.50–$3.00 per part. A SUS304 part needs no coating, but welding costs are 2–3x higher. Aluminum needs no coating but requires more expensive welding consumables and slower processing.
Here’s our decision framework when a customer asks for a material recommendation:
- Indoor, cost-driven: SPCC + powder coat. The default choice for 60% of our projects.
- Indoor, moderate corrosion, paintable: SECC + powder coat. Eliminates separate plating step.
- Indoor, electrical enclosure (EMI shielding): SECC or SPCC with zinc plating. Steel provides EMI shielding that aluminum doesn’t.
- Outdoor, general: SECC + powder coat, or SPCC + galvanize + powder coat for harsher environments.
- Marine or coastal: SUS316 stainless, or aluminum 5052 for weight-sensitive parts.
- Food, medical, or pharmaceutical: SUS304 (or SUS316 for higher corrosion resistance). No coating means no flaking or contamination risk.
- Weight-sensitive (aerospace, automotive, portable): Aluminum 5052 for formed parts, 6061 for structural/machined parts.
- Heat dissipation enclosure: Aluminum 5052 or 6061, possibly anodized for additional surface hardness.
One more thing: don’t over-specify
The most common material selection mistake I see from B2B buyers is over-specifying. Not every enclosure needs SUS304. Not every bracket needs 6061-T6 aluminum. If your part lives indoors in a controlled environment and will be powder coated, SPCC is the right answer — choosing stainless “just to be safe” adds 4x to your material cost for zero practical benefit.
The second most common mistake is under-specifying — using SPCC for an outdoor part because it’s cheaper, then dealing with rust failures in the field. The total cost of a field failure (warranty replacement, shipping, reputation) is always higher than the cost of specifying the right material upfront.
If you’re not sure which material your part needs, send us the drawing and the application details. We’ll recommend the most cost-effective material that will actually work in your environment — not the most expensive one. You can also browse our product portfolio to see examples of what we’ve made in each material.
Not Sure Which Material to Choose?
Send us your drawing and application details. We’ll recommend the most cost-effective material for your environment — and explain why. No upselling, just engineering advice.