Stainless Steel 304 and 316 — Grades for Strength and Corrosion Resistance
When your part must resist corrosion, hold cosmetic finish and survive harsh environments, stainless steel is the material. At SkillsProto we CNC machine, sheet-metal fabricate and die cast with 304 (1.4301) and 316 (1.4401) stainless for food, marine, medical and chemical applications.
If your part touches water, food, chemicals or outdoor environments, stainless is the safe long-term bet.
304 vs 316 at a glance
| Property | Stainless 304 | Stainless 316 |
|---|---|---|
| Chromium content | 18% | 16–18% |
| Nickel content | 8% | 10–14% |
| Molybdenum | 0% | 2–3% |
| Corrosion resistance | Very good (most environments) | Superior (chloride / marine / chemical) |
| Magnetic | Slightly (after forming) | Slightly (after forming) |
| Tensile strength | 515 MPa | 515 MPa |
| Machinability | Fair (work hardens) | Easy (free-machining 316L) |
| Weldability | Excellent | Excellent |
| Typical cost | Lower | Higher (~20–30%) |
| Common uses | Kitchen equipment, panels, brackets | Marine hardware, medical implants, chemical tanks |
When to choose 304
- Indoor applications, food contact (kitchen, processing equipment).
- General panels, brackets, structural parts.
- Cost-sensitive projects.
When to choose 316
- Marine / outdoor / chloride exposure (saltwater, swimming pools).
- Medical and pharmaceutical equipment (higher corrosion resistance, easier to passivate).
- Chemical handling, brewery equipment.
Machining notes
- Stainless work hardens — sharp tools and steady feeds are essential to avoid heat buildup.
- We use dedicated stainless tooling and lower surface feet per minute to maintain tolerance.
- Tolerances to ±0.05 mm on critical features.
- Lead time typically 5–10 working days for prototypes.
Finishing options
- Passivation — citric or nitric acid passivation to maximise corrosion resistance.
- Electropolishing — smooth, hygienic, ultra-clean surface for medical / food.
- Bead blasting — uniform matte finish.
- Brushed / polished — directional satin (4-grit, 6-grit) or mirror polish.
- Powder coating (over primer) for coloured stainless parts.
Frequently Asked Questions
Q1: Should I use 304 or 316 for outdoor enclosures? A: 316. The molybdenum protects against chloride pitting in marine and polluted environments.
Q2: Can stainless be anodised? A: No — anodising is an aluminium process. Stainless parts are coloured by PVD coating, powder coating over primer, or electropolishing for cosmetic finish.
Q3: Do you provide material certificates? A: Yes — mill certificates are available on request for traceable batches.