SUS316L vs 304L stainless steel: Chloride corrosion

When selecting stainless steel for industrial applications, understanding how chlorides affect corrosion is critical. Two commonly used low-carbon austenitic stainless steels, SUS304L and SUS316L, behave differently in environments with chlorides such as seawater, salt spray, and chemical solutions.

What is the material equivalent of SUS316L?

SUS316L (Japanese JIS standard) is a low-carbon austenitic stainless steel primarily equivalent to AISI 316L (USA) and EN 1.4404 (X2CrNiMo17-12-2, Europe). It is also designated as UNS S31603, which ensures similar high corrosion resistance, particularly for welded components.

 

What is SUS304 material equivalent to?

SUS304 is a Japanese industrial standard (JIS) for the most common austenitic stainless steel, with its primary equivalent being AISI 304 (American standard). Other common international equivalents include EN 1.4301 (European/German)SUS304 (Japanese), and 0Cr18Ni9 (Chinese), generally known as 18/8 stainless steel.

SUS316L vs 304L stainless steel :chemical composition

Grade	Carbon (C)	Chromium (Cr)	Nickel (Ni)	Molybdenum (Mo)	Remarks
SUS304L	≤0.03%	18–20%	8–12%	0%	Standard austenitic stainless steel
SUS316L	≤0.03%	16–18%	10–14%	2–3%	Mo increases chloride resistance

 

SUS316L vs 304L stainless steel: Pitting resistance

Chloride-induced pitting is a major problem in environments such as seawater, salt solutions or industrial brines.
304L: Pitting is prone to occur in chloride concentrations > 200 ppm (e.g. brackish water). Its pitting resistance equivalent value (PREN) ≈ 19-22 (calculated as PREN = %Cr + 3.3×%Mo + 16×%N), lack of Mo leads to poor pitting resistance.
316L: Adding Mo (PREN ≈ 24-26) can form a more stable passive film, delaying the occurrence of pitting corrosion. It can still resist pitting corrosion in environments with chloride concentrations up to about 1,000 ppm (e.g., moderate seawater exposure).

 

SUS316L vs 304L stainless steel: Crevice corrosion resistance

Crevice corrosion occurs in confined spaces (e.g., gaskets, bolted joints) where chloride ions gather.
304L: Due to the limited Mo content, crevice corrosion is prone to occur at temperatures above 50°C in chloride-rich environments.
316L: Mo improves crevice corrosion resistance by stabilizing the passive film in an oxygen-deficient acidic microenvironment. For applications where crevices are unavoidable (e.g., heat exchangers, marine equipment).

 

SUS316L vs SUS304L : Mechanical Properties

Property	SUS304L	SUS316L
Tensile Strength (MPa)	≥ 485 MPa	≥ 485 MPa
Yield Strength (0.2% Offset, MPa)	≥ 170 MPa	≥ 170 MPa
Elongation (%)	≥ 40%	≥ 40%
Hardness (HB)	≤ 187 HB	≤ 187 HB
Hardness (HRB)	≤ 90 HRB	≤ 90 HRB
Modulus of Elasticity	~193 GPa	~193 GPa
Density	7.93 g/cm³	8.00 g/cm³

 

SUS316L vs 304L stainless steel: Applications in chloride environments

304L: For low chloride environments (e.g., indoor water systems, mild food processing, non-salt environments).
316L: For aggressive chloride environments, such as:
Seawater applications (marine hardware, desalination plants).
Chemical processing (chloride-containing acids, brines).
Pharmaceutical/biotech equipment (cleaning with chlorine-containing disinfectants).
Paper mills (bleaching solutions containing chloride ions).

 

SUS316L vs 304L stainless steel: Limitations

Neither steel grade is completely resistant to stress corrosion cracking (SCC) in high temperature, high chloride environments (e.g., > 60°C, > 1,000 ppm Cl⁻). In extreme conditions, super austenitic stainless steels (e.g., 904L) or duplex stainless steels may be required.

 

Need Help Selecting Between SUS304 and SUS316L?
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