Its low carbon content also makes it particularly useful for welded tanks, piping, vessels and fabricated process equipment where resistance to intergranular corrosion after welding is important.

However, 316L is not a universal chemical or refinery alloy.

The correct material selection must be based on the actual process fluid, concentration, temperature, chloride content, pressure, contaminants, welding condition and equipment design.

What Is 316L Stainless Steel?

316L is a low-carbon molybdenum-alloyed austenitic stainless steel.

Common international designations include:

• ASTM: Type 316L;
• UNS: S31603;
• EN: 1.4404;
• EN name: X2CrNiMo17-12-2;
• JIS: SUS316L.

For JUDE material information, see

316L Stainless Steel
.

Why Does Molybdenum Matter?

The main alloying distinction between the common 304L and 316L families is the molybdenum addition in 316L.

Molybdenum improves resistance to localized corrosion such as pitting and crevice corrosion in many chloride-containing environments.

This makes 316L worth evaluating where 304L does not provide sufficient corrosion margin.

Why Is the Low Carbon Level Important?

The lower carbon level reduces the tendency for chromium carbide precipitation during welding.

This is particularly valuable in:

• large tanks;
• welded process vessels;
• pipe spools;
• heat-exchanger fabrication;
• large fabricated chemical equipment.

Low carbon reduces sensitization risk but does not remove the need for qualified welding procedures and proper post-weld surface treatment.

316L Standards and Grade Identification

Which Chemical and Petrochemical Equipment Uses 316L?

316L Chemical Storage Tanks

Chemical storage tanks are one of the most important applications for 316L flat products.

Potential fabricated parts include:

• shell courses;
• bottom plates;
• roofs;
• nozzles;
• internal partitions;
• access covers.

Before specifying 316L, the tank designer should confirm the chemical concentration, temperature, chloride content, expected contamination and cleaning procedure.

316L Process Vessels and Reactor Shells

316L can be fabricated into atmospheric or pressure-containing process vessels when permitted by the design code and project material specification.

Material review should include:

• feed chemistry;
• reaction products;
• impurities;
• temperature;
• pressure;
• startup and shutdown conditions;
• cleaning chemistry.

316L Process Piping and Pipe Spools

TP316L is widely used in compatible process piping systems.

For finished ASTM stainless steel pipe, ASTM A312/A312M is a common specification.

Typical purchasing information includes:

• NPS / OD;
• wall thickness or schedule;
• welded or seamless construction;
• pipe standard;
• end preparation;
• testing requirements;
• process medium.

316L Heat Exchangers and Condensers

316L is widely evaluated for heat exchangers because the Mo-bearing alloy provides greater localized-corrosion resistance than 304L.

However, both sides of the exchanger must be reviewed.

Important parameters include:

• process fluid;
• cooling water;
• chloride concentration;
• temperature;
• flow velocity;
• crevices;
• deposits;
• shutdown conditions.

316L Flanges and Valves

Flanges and valves are established 316L application categories.

Depending on the component, the required material may be supplied as:

• plate;
• bar;
• forging;
• casting;
• machined stock.

The correct product specification must match the manufacturing route.

316L in Petrochemical Equipment

316L is widely used in the chemical and petrochemical industries, but the specific process stream must control the final grade decision.

Potential applications include:

• process vessels;
• storage systems;
• transfer piping;
• heat exchangers;
• valves;
• flanges;
• tank-container systems.

316L in Selected Refinery Applications

316L can be used in selected refinery environments where the corrosion mechanism falls within its capabilities.

Refinery metallurgy can be affected by:

• sulfur compounds;
• naphthenic acids;
• chlorides;
• acidic condensates;
• wet hydrogen sulfide;
• high temperature;
• shutdown corrosion.

316L in Chloride-Containing Environments

The molybdenum content of 316L improves resistance to pitting and crevice corrosion compared with 304L.

However, risk increases with:

• higher chloride concentration;
• higher temperature;
• lower pH;
• crevices;
• deposits;
• stagnant conditions.

Chloride Stress-Corrosion Cracking

316L is still a conventional austenitic stainless steel and can suffer chloride-induced stress-corrosion cracking under sufficiently aggressive conditions.

This is especially important when heat, tensile stress and chloride concentration act together.

Is 316L Resistant to Hydrochloric Acid?

316L should not be generically described as hydrochloric-acid resistant.

Hydrochloric acid can destroy the passive film that protects stainless steel.

Material suitability depends strongly on:

• acid concentration;
• temperature;
• impurities;
• aeration;
• process conditions.

More highly alloyed stainless steels or nickel alloys are frequently required.

316L in Sulfuric Acid

Sulfuric-acid resistance cannot be summarized by a single statement.

The corrosion rate can vary dramatically with:

• acid concentration;
• temperature;
• oxygen;
• metal ions;
• other contaminants.

A corrosion chart, laboratory test or project metallurgy specification should be used for final material selection.

316L and H₂S / Sour Service

Sour-service suitability must be evaluated from the complete environment rather than the stainless steel grade name alone.

Relevant parameters include:

• H₂S partial pressure;
• pH;
• chloride concentration;
• CO₂;
• temperature;
• stress;
• applicable NACE / ISO requirements.

316L and Elevated Temperature

The low carbon content of 316L is beneficial for welded fabrication, but it does not make 316L the preferred material for every prolonged high-temperature refinery application.

When high-temperature stability, oxidation, carburization or sulfidation becomes the controlling issue, stabilized or heat-resistant stainless steels may be more appropriate.

304L vs 316L vs 317L for Process Equipment

See JUDE’s

304L Stainless Steel

and

317L Stainless Steel

pages for comparison.

316L Sheet, Plate, Coil or Strip?

316L Plate

Plate is commonly used for:

• large tanks;
• process vessels;
• reactor shells;
• pressure equipment;
• large fabricated components.

See JUDE’s

Stainless Steel Sheet and Plate
.

316L Coil

Stainless Steel Coil

can be suitable for continuous production, thinner-gauge tanks, fabricated components and downstream forming.

316L Strip

Stainless Steel Strip

is suitable for narrow-width formed parts, clamps and specialized fabricated components.

Fabrication and Welding of 316L

316L is widely used in welded chemical equipment.

Fabricators should still control:

• heat input;
• filler metal;
• joint design;
• shielding;
• interpass temperature;
• heat tint;
• surface contamination.

Weld oxide and iron contamination can reduce the corrosion performance of the final component.

Depending on the specification, post-fabrication treatment may include:

• mechanical cleaning;
• pickling;
• passivation;
• final rinsing;
• visual inspection.

Incoming Inspection of 316L

1. Confirm Type 316L / UNS S31603 or the specified EN/JIS grade.
2. Verify the governing product standard.
3. Review the MTC.
4. Match heat and plate/coil numbers.
5. Verify thickness.
6. Verify width and length.
7. Inspect surface condition.
8. Check flatness and tolerance.
9. Perform PMI when the project requires it.
10. Verify Mo-bearing alloy identity where required.
11. Review additional corrosion tests when specified.
12. Verify project documentation.

See JUDE’s

Inspection Reports

for available material-verification documentation.

Common 316L Purchasing Mistakes

JUDE 316L Stainless Steel Supply Options

JUDE lists 316L across its stainless steel flat-product range.

• 
  316L Stainless Steel
  
• 
  Stainless Steel Sheet / Plate
  
• 
  Рулон нержавеющей стали
  
• 
  Полоса из нержавеющей стали
  
• 
  Обработка полос
  

316L Chemical / Petrochemical RFQ Checklist

1. Final equipment: tank, vessel, pipe, exchanger, valve or another component.
2. Industry: chemical, petrochemical, refinery or other.
3. Process fluid.
4. Concentration.
5. Normal operating temperature.
6. Maximum design temperature.
7. Pressure.
8. Chloride concentration.
9. pH.
10. H₂S / sulfur / acid contaminants if applicable.
11. Grade: 316L / S31603 / 1.4404 / SUS316L.
12. Product standard.
13. Product form: plate, sheet, coil or strip.
14. Thickness.
15. Width and length.
16. Surface finish.
17. Dimensional tolerances.
18. Welding process.
19. Post-weld cleaning requirement.
20. PMI requirement.
21. MTC / EN 10204 requirement.
22. Corrosion test requirement.
23. Quantity.
24. Destination and Incoterm.

Frequently Asked Questions

Заключение

316L stainless steel is one of the most important standard materials used in chemical and petrochemical process equipment.

Its combination of molybdenum-enhanced localized-corrosion resistance and low-carbon welded performance makes it suitable for many chemical tanks, process vessels, piping systems, heat exchangers, flanges and valves.

The correct selection sequence is:

Process Fluid → Concentration → Temperature → Chlorides → Contaminants → Corrosion Mechanism → Grade → Product Standard → Fabrication → Inspection.

316L provides more corrosion margin than 304L in many environments, but it is not a universal solution for seawater, hydrochloric acid, chloride SCC, sour service or refinery corrosion.

When the service environment exceeds the capability of 316L, 317L, duplex stainless steels, higher-alloy austenitic grades or nickel alloys should be evaluated.

Technical References

• 
  ASTM A240/A240M-26
  
• 
  ASTM A480/A480M-25b
  
• 
  ASTM A312/A312M-25
  
• 
  Outokumpu Supra 316L / 1.4404
  
• 
  Nickel Institute — Stainless Steels for Chemical Process Equipment
  
• 
  Nickel Institute — Role of Stainless Steel in Petroleum Refining