316 Stainless Steel: Molybdenum-Added Corrosion-Resistant Upgrade Grade

316 stainless steel is an upgraded corrosion-resistant grade based on 304, with the addition of 2%-3% molybdenum. Molybdenum can enhance the stability of the passivation film, significantly improving resistance to pitting and crevice corrosion in chloride ion environments. It is the preferred material for harsh corrosion scenarios such as marine and chemical industries.

Core Parameters

Chemical Composition (wt%): C≤0.08, Si≤1.00, Mn≤2.00, P≤0.045, S≤0.030, Cr=16.00-18.00, Ni=10.00-14.00, Mo=2.00-3.00, Fe=Balance

Mechanical Properties (Annealed): Tensile Strength ≥515MPa, Yield Strength ≥205MPa, Elongation ≥40%, Brinell Hardness ≤217HB

Service Temperature: -196℃ to 870℃ (continuous service)

Equivalent Grades: SUS316 (JIS), EN 1.4401 (EN), UNS S31600 (ASTM)

Performance Advantages: Molybdenum addition makes its chloride ion corrosion resistance 3-5 times higher than that of 304; excellent corrosion resistance to weak acids (dilute sulfuric acid, acetic acid) and organic solvents; better high-temperature oxidation resistance than 304, maintaining stable performance at 870℃; high toughness, suitable for low-temperature applications down to -196℃.

Typical Applications: Marine engineering (ship components, offshore platform pipelines), chemical equipment (reaction kettles, pipelines for chloride-containing media), food processing equipment (pickling tanks), medical implants (meeting ISO 10993 biocompatibility standards), and coastal architectural decoration.

Practical Q&A

Q1: What is the core difference between 316 and 304 stainless steel? A1: The key is the addition of molybdenum in 316. In 3.5% NaCl solution tests, the annual corrosion rate of 316 is ≤0.005mm, while that of 304 is 0.02-0.05mm. Additionally, 316 has a higher nickel content, which further enhances toughness and high-temperature stability.

Q2: Can 316 stainless steel be used in seawater environments? A2: Yes. Its excellent resistance to seawater corrosion makes it suitable for long-term immersion components such as ship hulls and seawater desalination equipment. The annual corrosion rate in seawater is less than 0.005mm, which is far lower than that of 304.

Q3: Why is 316 more expensive than 304? A3: The main reason is the addition of molybdenum, which accounts for 60% of the price premium. Additionally, 316 has a higher nickel content (10-14% vs. 8-10.5% for 304), and the total raw material cost is 40-50% higher than that of 304.

Q4: Is 316 stainless steel suitable for low-temperature storage tanks (e.g., liquid nitrogen storage)? A4: Yes. It has excellent low-temperature toughness, with impact toughness ≥100J at -196℃, which can fully meet the requirements of low-temperature storage equipment. It should be noted that the welding process should be strictly controlled to avoid reducing low-temperature performance due to weld defects.

Q5: How to repair 316 stainless steel components with local corrosion? A5: First, grind off the corroded area with a grinder until the metal luster is exposed; then use ER316L welding wire for repair welding, ensuring full penetration; after welding, grind the weld to be smooth and perform passivation treatment with 20% nitric acid solution to restore the corrosion resistance of the surface.