What are the differences between SECC galvanized steel grades under different standards

What are the differences between SECC galvanized steel grades under different standards?
SECC galvanized steel grades under different standards vary significantly in terms of substrate material, coating characteristics, mechanical properties, and surface treatment. The following is a comparative analysis of the major standard systems:
1. Japanese JIS Standard (SECC)
Core Characteristics
Substrate: SPCC (cold-rolled mild steel), with moderate strength and excellent workability.
Coating: Electrolytic zinc plating, zinc coating codes E8-E32 (single-sided coating thickness 1.4-7.0μm), typically E20 (double-sided 20g/m²).
Surface Treatments: Chromic acid passivation (C), oiling (O), fingerprint resistance (N5), etc. The fingerprint resistance treatment (SECC-N5) reduces fingerprint residue and is suitable for home appliance panels.
Mechanical Properties: Yield strength ≥138MPa, tensile strength ≥270MPa, elongation 33%, suitable for medium-duration stamping.
Applications
Applications requiring high surface finish and dimensional accuracy include electronic device casings (laptops, mobile phone midframes) and appliance linings (microwave ovens, air conditioners).
II. European EN Standard (DC01+ZE)
Core Characteristics
Substrate: DC01 (mild carbon steel), with mechanical properties similar to SPCC, including a tensile strength of 270-410 MPa and an elongation of 28%.
Coating: Electrolytic zinc plating, coating code ZE25/25 (25 g/m² on both sides). Surface treatments include chromate or chromium-free passivation for enhanced environmental friendliness.
Processing: For general cold forming applications, stamping performance is slightly inferior to SECC but superior to SECD.
Applications
Applications requiring a balance between formability and corrosion resistance include automotive structural parts (instrument panel brackets) and appliance frames (washing machine control boxes). III. US ASTM Standard (CS type B)
Core Characteristics
Baseplate: Mild carbon steel (commercial-grade CS), with sufficient plasticity for general forming, a tensile strength of approximately 270-500 MPa, and high elongation.
Coating: Electrolytic zinc plating, with customizable coating weight (e.g., differentiated plating on one or both sides), and flexible surface treatment (passivation, oiling).
Performance: Suitable for simple bending and medium-level forming, requiring minimal performance requirements, at a low cost.
Applications: General structural parts (filing cabinet drawer slides), small stampings (connector terminals), etc.
IV. China GB Standard (DX51D+Z)
Core Characteristics
Baseplate: Mild carbon steel, with a tensile strength of 270-500 MPa, an elongation comparable to SECC, and deep-drawing performance approaching SECD. Coating: Electrolytic zinc or zinc-nickel alloy, with a wide range of coating weights (30-275g/m²). Surface treatments include passivation and phosphating, with phosphating (DX51D+Z-P) being suitable for pre-painting.
Corrosion Resistance: The coating is relatively thick (e.g., Z150 = 150g/m² on both sides), and can withstand 240 hours of salt spray testing without red rust, surpassing the indoor corrosion resistance of SECC.
Applications: Building materials (roofing panels), appliance covers (refrigerator doors), and other applications where corrosion resistance and cost are critical.