JIS G3125 SPA-H is a Japanese industrial standard covering hot-rolled weathering steel plates. Compared with conventional carbon steel, SPA-H steel provides enhanced atmospheric corrosion resistance.
As a weathering steel material, SPA-H steel coil naturally develops a protective oxide patina on its surface when exposed to the environment, giving it a distinctive rustic appearance while protecting the base metal.
The chemical composition of JIS G3125 SPA-H strip mainly consists of carbon, silicon, manganese, phosphorus, sulfur, copper, chromium, and nickel.
The steel offers a minimum tensile strength of 490 MPa and a minimum yield strength of 355 MPa, making it suitable for demanding structural applications. SPA-H steel plates are widely applied in construction projects, economizers, air preheaters, and railway vehicles.
SPA-H weathering steel combines the advantages of ordinary structural steel-such as good formability, high strength, and excellent fatigue resistance-with significantly improved corrosion resistance. Its resistance to atmospheric corrosion is typically 2 to 8 times higher than that of standard carbon steel.
Also referred to as atmospheric corrosion-resistant steel, SPA-H is a low-alloy steel positioned between carbon steel and stainless steel. It is produced by adding controlled amounts of copper and corrosion-resistant alloying elements such as phosphorus, chromium, nickel, titanium, and vanadium to carbon steel.
As a result, SPA-H steel not only retains the mechanical performance of conventional steel but also delivers long-term durability in outdoor environments.
Due to these superior properties, SPA-H weathering steel is relatively expensive. Compared with ordinary carbon steel, its market price is typically around 60% higher.
Therefore, SPA-H steel is generally reserved for applications with harsh service conditions and strict corrosion-resistance requirements, such as shipping containers, railway vehicles, oil derricks, drilling platforms, and other exposed structures.
JIS G3125 SPA-H Plate Specification
| Plate Thickness | Width | Plate Equivalent |
|---|---|---|
| 2.5–25 mm | 50–2500 mm | ASTM A588, HW350 |
| Process | Application | Form |
|---|---|---|
| Dry, pickled & oiled | Railway rolling stock, architectural structures | Coil, strip, plate, sheet |
JIS G3125 SPA-H Sheet Equivalent Grades
| Japan (JIS) | ISO | Germany (DIN/WNr) | EU (EN) | England (BS) | France (AFNOR) | Italy (UNI) | European Old | China (GB) |
|---|---|---|---|---|---|---|---|---|
| SPA-H | Fe355W-1A | 9CrNiCuP324 | S355J0WP (1.8945) | WR50A | E36WA3 | Fe510C1K1 | Fe510C1KI | 09CuPCrNi-A |
| S355JOWP | WR50B | |||||||
| WR50C |
Mechanical Properties of SPA-H Steel Plate
| Grade | Elongation | Yield Strength | Plate Thickness | Tensile Strength |
|---|---|---|---|---|
| SPA-H | ≥ 22% | ≥ 355 MPa | ≤ 6.0 mm | ≥ 490 MPa |
| SPA-H | ≥ 15% | ≥ 355 MPa | > 6.0 mm | ≥ 490 MPa |
Chemical Composition of JIS G3125 SPA-H Steel Plate
| Grade | Si | C ≤ | P | Mn ≤ | S ≤ | Cr | Cu | Ni ≤ |
|---|---|---|---|---|---|---|---|---|
| SPA-H | 0.20–0.75 | 0.12 | 0.070–0.150 | 0.60 | 0.035 | 0.30–1.25 | 0.25–0.55 | 0.65 |
Q1: What is SPA-H Corten steel?
SPA-H is a Japanese standard weathering steel grade specified in JIS G 3125. It contains alloying elements such as copper, chromium, and nickel, which allow it to form a dense protective rust layer on the surface. This patina significantly slows down further corrosion and improves long-term durability in atmospheric environments.
Q2: What are the main advantages of SPA-H weathering steel?
The key advantages of SPA-H steel include excellent atmospheric corrosion resistance, high strength, and low maintenance cost. Unlike ordinary carbon steel, SPA-H does not require frequent painting or coating, which helps reduce lifecycle costs while maintaining a unique natural appearance.
Q3: Where is SPA-H Corten steel commonly used?
SPA-H steel is widely used in bridges, building structures, architectural façades, railway carriages, containers, air preheaters, and economizers. It is especially suitable for outdoor structures exposed to changing weather conditions for long periods.
Q4: Does SPA-H steel need painting or surface treatment?
In most outdoor applications, no additional painting is required. SPA-H naturally forms a stable rust layer after exposure to the atmosphere. However, in highly corrosive environments (such as marine or high-salt areas), additional surface protection may be recommended to extend service life.
Q5: How long does it take for SPA-H steel to form a stable patina?
Under normal atmospheric conditions, SPA-H steel typically forms a stable protective patina within 6 to 24 months
