When it comes to selecting stainless steel plates for corrosive industrial applications, 904L stainless steel plate and 316L stainless steel plate are two top contenders. Both are highly corrosion-resistant austenitic stainless steels, but they differ significantly in composition, performance, and pricing.
This comprehensive guide provides an in-depth comparison to help engineers, buyers, and fabricators make an informed decision based on application, corrosion environment, budget, and processing requirements.
Introduction to Austenitic Stainless Steels
904L stainless steel plate and 316L stainless steel plate are non-magnetic, low-carbon, austenitic alloys. They are known for:
- Exceptional corrosion resistance
- High ductility and toughness
- Good weldability and fabrication capabilities
However, 904L stainless steel plate was specifically developed to offer greater corrosion resistance in extremely aggressive conditions, particularly in environments containing reducing acids like sulfuric acid.
Chemical Composition
| Element | 316L Plate (%) | 904L Plate (%) |
|---|---|---|
| Chromium | 16.0 – 18.0 | 19.0 – 23.0 |
| Nickel | 10.0 – 14.0 | 23.0 – 28.0 |
| Molybdenum | 2.0 – 3.0 | 4.0 – 5.0 |
| Copper | ≤ 0.5 | 1.0 – 2.0 |
| Carbon | ≤ 0.03 | ≤ 0.02 |
Analysis:
The higher content of nickel, molybdenum, and copper in 904L stainless steel plate significantly improves resistance to acidic and chloride-rich environments. 316L stainless steel plate has a more balanced composition suitable for general industrial use.
Corrosion Resistance
316L stainless steel plate offers:
- Excellent resistance in moderately aggressive environments
- Reliable protection against pitting, crevice corrosion, and atmospheric exposure
- Common in marine environments and chemical equipment
904L stainless steel plate provides:
- Outstanding resistance to sulfuric, phosphoric, and acetic acids
- Excellent performance in chloride-rich and reducing conditions
- High resistance to intergranular corrosion, even after welding
904L stainless steel plate is often chosen for chemical process tanks, pickling lines, and offshore structures where long-term resistance is critical.
Mechanical and Physical Properties
| Property | 316L Plate | 904L Plate |
|---|---|---|
| Density (g/cm³) | 8.00 | 8.05 |
| Tensile Strength (MPa) | ~485 | 490 – 710 |
| Yield Strength (MPa) | ~170 | ~220 |
| Elongation (%) | ~40 | ~35 |
| Hardness (HB) | ≤ 150 | ≤ 220 |
| Thermal Conductivity | 16.3 W/m·K | 12 W/m·K |
Summary:
- 904L stainless steel plate is stronger and harder.
- 316L stainless steel plate has slightly better formability and thermal conductivity.
- For applications requiring dimensional stability and strength under load, stainless steel 904L plate is preferred.
Fabrication and Weldability
316L Stainless Steel Plate:
- Easily machined and fabricated
- Suitable for forming, bending, and welding using common methods (TIG, MIG, SAW)
- No post-weld heat treatment required
904L Stainless Steel Plate:
- Weldable but requires expertise and proper filler (ER385)
- Higher strength makes it harder to machine
- Post-weld pickling and passivation are necessary to restore corrosion resistance
In fabrication-heavy projects, 316L stainless steel plate is more cost-efficient and easier to work with.
High Temperature Performance
- 316L stainless steel plate can be used up to 870°C intermittently and 925°C continuously but may suffer from sensitization.
- 904L stainless steel plate maintains mechanical properties and corrosion resistance under prolonged high-temperature exposure, especially in acidic conditions.
Applications involving hot sulfuric acid or elevated temperature acid vapors benefit from stainless steel 904L plate.
Surface Finishes and Availability
Finishes:
Both plates are available in:
- 2B (cold rolled, dull finish)
- No. 1 (hot rolled, annealed & pickled)
- BA (bright annealed)
- No. 4 (brushed satin finish)
- No. 8 (mirror finish)
Availability:
- 316L stainless steel plate is widely available in a range of thicknesses and sizes.
- 904L stainless steel plate is less commonly stocked, may require special order, and is typically supplied with mill test certification.
Common Applications
316L Stainless Steel Plate:
- Marine equipment and shipbuilding
- Food and dairy processing
- Pharmaceutical manufacturing
- Chemical storage tanks
- Heat exchangers
904L Stainless Steel Plate:
- Acidic chemical storage vessels (sulfuric, nitric, phosphoric)
- Flue gas scrubbers and gas treatment systems
- Desalination plants and offshore rigs
- Paper and pulp industry
- Pickling equipment and acid pipelines
Price Comparison (India)
- 316L stainless steel plate price per kg: ₹280 – ₹350
- 904L stainless steel plate price per kg: ₹550 – ₹750
While 904L stainless steel plate is significantly more expensive, it delivers superior performance in the most challenging environments—often justifying its cost with longer service life and reduced maintenance.
Selection Guide
| Criteria | Choose 316L Plate | Choose 904L Plate |
|---|---|---|
| Moderate corrosion | ✓ | ✓✓ |
| Strong acid exposure | ✗ | ✓✓✓ |
| Ease of fabrication | ✓✓✓ | ✓ |
| High mechanical strength | ✓ | ✓✓ |
| Availability and cost | ✓✓✓ | ✗ (higher cost, lower availability) |
| Long-term durability in acids | ✓ | ✓✓✓ |
Conclusion
Both 904L stainless steel plate and 316L stainless steel plate are reliable choices, but their performance varies based on the application. If your environment involves chloride exposure or marine conditions, 316L stainless steel plate is a practical and economical solution.
However, if you’re dealing with highly acidic environments, strong reducing agents, or need long-term corrosion resistance in extreme settings, 904L stainless steel plate is the ideal material for extended durability and safety.
