Stainless steel used in seawater environments must possess excellent corrosion resistance, along with good mechanical properties and heat resistance. Commonly used stainless steel materials include 304, 316, 316L, and 2205.
304 Stainless Steel
304 stainless steel is a general-purpose stainless steel composed of 18% chromium and 8% nickel. It offers good corrosion resistance and toughness, but its resistance to chloride ion corrosion is limited. Therefore, it is not suitable for use in seawater with high salinity or environments with high concentrations of chloride ions.
316 Stainless Steel
316 stainless steel contains 18% chromium, 10% nickel, and 2-3% molybdenum. This addition of molybdenum significantly enhances its corrosion resistance, particularly in chloride-rich environments such as seawater. 316 stainless steel maintains its mechanical properties and corrosion resistance even under high temperatures and extended exposure to seawater.
316L Stainless Steel
316L stainless steel is a low-carbon version of 316 stainless steel, designed to further improve corrosion resistance, especially in extreme environments. Compared to 316, 316L offers superior resistance to pitting and crevice corrosion, making it ideal for use in more aggressive seawater conditions.
2205 Stainless Steel
2205 stainless steel is a duplex stainless steel alloy containing 22% chromium, 5% nickel, and 3% molybdenum. This composition gives it high strength, excellent corrosion resistance, and superior wear resistance. 2205 is well-suited for extreme seawater environments, including submarine pipelines, ships, and offshore platforms, where both mechanical strength and corrosion resistance are critical.
Comparative analysis table of various stainless steel materials
| Material | Corrosion Resistance | Mechanical Properties | Heat Resistance |
| 304 | Good resistance to most environments; susceptible to pitting corrosion in chloride environments (e.g., seawater). | Yield Strength: 215–290 MPa | Good heat resistance; can withstand up to 870°C. Susceptible to intergranular corrosion at high temperatures. |
| Ultimate Tensile Strength: 500–700 MPa | |||
| Elongation: >40% | |||
| 316 | Excellent corrosion resistance, especially in chloride environments due to the addition of molybdenum (Mo). | Yield Strength: 290–400 MPa | Similar to 304, can withstand up to 870°C with better high-temperature oxidation and creep resistance. |
| Ultimate Tensile Strength: 580–720 MPa | |||
| Elongation: >40% | |||
| 316L | Similar to 316 but with lower carbon content (<0.03%), which enhances weldability and resistance to intergranular corrosion. | Yield Strength: 290–400 MPa | Same as 316, good heat resistance up to 870°C, especially for welded structures. |
| Ultimate Tensile Strength: 580–720 MPa | |||
| Elongation: >40% | |||
| 2205 | Excellent resistance to stress corrosion cracking (SCC) and pitting, especially in seawater and aggressive chemicals. | Yield Strength: 450–620 MPa | Lower heat resistance compared to 304/316; recommended for use between 300°C and 600°C. Prolonged exposure to high temperatures may reduce corrosion resistance. |
| Ultimate Tensile Strength: 620–900 MPa | |||
| Elongation: >25% |
According to the actual application requirements, choosing the right stainless steel material can improve the service life and economic benefits of the equipment.
