SUS310S vs SUS304 Stainless Steel: Corrosion Resistance Compared

Two Austenitic Grades, Different Corrosion Limits

SUS310S is a high-chromium, high-nickel austenitic stainless steel defined in the JIS system, while SUS304 is the general-purpose 18-8 austenitic grade. Although both are austenitic and non-magnetic in the annealed condition, the large difference in chromium and nickel content produces very different corrosion and oxidation behavior. SUS310S is chosen for high-temperature and moderately aggressive chemical service; SUS304 is chosen for general industrial and food-contact service at moderate temperatures.

Chemical Composition (JIS G4304 / G4305)

Composition ranges per JIS G4304 and G4305 for SUS310S and SUS304, in weight percent:

Element	SUS310S	SUS304
Carbon (C)	0.08 max	0.08 max
Silicon (Si)	1.50 max	1.00 max
Manganese (Mn)	2.00 max	2.00 max
Phosphorus (P)	0.045 max	0.045 max
Sulfur (S)	0.030 max	0.030 max
Chromium (Cr)	24.00-26.00	18.00-20.00
Nickel (Ni)	19.00-22.00	8.00-10.50
Molybdenum (Mo)	Not specified	Not specified

Corrosion Resistance Comparison

Oxidizing environments: the dense chromium oxide passive layer of SUS310S provides oxidation resistance up to about 1200 degrees C in continuous use, while SUS304 is limited to about 870 degrees C and scales rapidly above that. Acidic environments: the high nickel content of SUS310S improves resistance to non-oxidizing acids such as dilute sulfuric and hydrochloric acid at elevated temperature, and it tolerates moderate concentrations of sulfuric acid up to roughly 50% as well as dilute nitric acid; SUS304 resists dilute nitric acid but corrodes readily in sulfuric or hydrochloric acid, especially hot and concentrated. Chloride environments: the higher chromium and nickel of SUS310S raise its pitting resistance equivalent number, giving better chloride resistance than SUS304 but still below molybdenum-bearing grades such as SUS316, so both grades are limited to low-chloride applications. Intergranular corrosion: the low-carbon design of SUS310S minimizes chromium carbide precipitation and intergranular attack without post-weld stabilization, while standard SUS304 can sensitize when heated in the 450-850 degrees C range during welding; for welded 304-type service, SUS304L or stabilized SUS321 should be used.

Application Selection Table

Application	Recommended Grade	Reason
High-temperature furnace parts, radiant tubes, burner components	SUS310S	Oxidation resistance to about 1200 degrees C
Chemical equipment for dilute acids	SUS310S	High chromium and nickel resist acid attack
Food and medical machinery, kitchen equipment	SUS304	Cost-effective for mild corrosion service with water and organic acids
Marine and seawater service	Neither	Require molybdenum-bearing grades such as SUS316 or duplex grades

Mechanical Properties at a Glance

In the solution-annealed condition both grades meet the typical JIS minima of 520 MPa tensile strength and 205 MPa yield strength (0.2% offset), with elongation of 40% minimum. SUS310S additionally develops useful creep strength in the 800-1000 degrees C range, which is the main reason it appears in fired heater and furnace designs where SUS304 would lose strength rapidly.

Frequently Asked Questions

What is the difference between SUS310S and SUS304? SUS310S has 24-26% chromium and 19-22% nickel versus 18-20% chromium and 8-10.5% nickel for SUS304. The higher alloy content gives SUS310S roughly 300 degrees C more oxidation resistance and better acid resistance, at higher material cost.

What is the maximum service temperature of SUS310S? In oxidizing atmospheres SUS310S is commonly rated for continuous service up to about 1200 degrees C and can withstand intermittent exposure at higher peaks, provided mechanical loading stays within allowable stresses.

Is SUS310S suitable for seawater? No. Neither SUS310S nor SUS304 contains molybdenum, so both are prone to pitting and crevice corrosion in chloride-rich environments such as seawater; molybdenum-bearing SUS316 or duplex grades are required there.

Which is better, SUS310S or SUS304, for high-temperature furnace parts? SUS310S. Its dense chromium oxide scale remains protective to about 1200 degrees C, while SUS304 scales above roughly 870 degrees C.

Does SUS310S resist intergranular corrosion after welding? Yes, better than standard SUS304. The low-carbon composition of SUS310S limits chromium carbide precipitation in the 450-850 degrees C sensitization range, so it is normally used in the as-welded condition.

What are the JIS standard references for these grades? SUS310S and SUS304 plate, sheet and strip are covered by JIS G4304 and G4305; bars and sections are covered by JIS G4303. The corresponding ASTM designations are UNS S31008 and UNS S30400 under ASTM A240.