Electrogalvanized (EG) Steel Coil: Technical Specifications & Industrial Applications
Material Definition & Process Overview
Electrogalvanized (EG) steel refers to cold-rolled steel coated with a zinc layer (5-20μm) through electrolytic deposition. Unlike hot-dip galvanizing, this low-temperature process (<50°C) preserves base metal mechanical properties while achieving precise coating control.
Key Process Stages
- Surface Preparation
- Alkaline degreasing (pH 11-13 @ 60-70°C)
- Acid pickling (HCl 15% @ 25°C, Fe²+ <120g/L)
- Electroplating
- Zinc anode composition: 99.995% Zn
- Current density: 20-60 A/dm²
- Bath chemistry: ZnSO₄·7H₂O (300g/L), H₃BO₃ (30g/L)
- Post-Treatment
- Chromate passivation (Cr³+ 3-5g/L, pH 4.0-4.5)
- Oiling (cationic anti-fingerprint, 0.5-1.5g/m²)
Material Classification & Standards
| Base Steel Grade (JIS) | EG Designation | Coating Weight (g/m²) | Typical Thickness |
|---|---|---|---|
| SPCC (Commercial) | SECC | 10-20 | 0.3-2.0mm |
| SPCD (Drawing) | SECD | 15-30 | 0.5-3.0mm |
| SPCE (Deep Drawing) | SECE | 20-40 | 0.8-3.2mm |
| SPCF (Extra Deep) | SECF | 30-60 | 1.0-4.5mm |
Product Parameters
| Product Name | Galvanized Coil |
| Thickness | 0.12mm-3.5mm |
| Width | 600mm-1500mm |
| Length | 508mm/610mm, Support Customization |
| Standard | AISI, ASTM, DIN, JIS, GB, JIS, SUS, EN, etc. |
| Zinc Layer | Hot Galvanizing: 60-275g/m² |
| Pre-galvanized: 80-275g/m² |
Chemical Composition
| Standard | Grade | C | Si | Mn | P | S | Ti |
| Forcold Forming
Chinese Standard |
DX51D+Z | 0.12 | 0.50 | 0.60 | 0.100 | 0.045 | 0.30 |
| DX52D+Z | 0.12 | 0.50 | 0.60 | 0.100 | 0.045 | 0.30 | |
| DX53D+Z | 0.12 | 0.50 | 0.60 | 0.100 | 0.045 | 0.30 | |
| DX54D+Z | 0.12 | 0.50 | 0.60 | 0.100 | 0.045 | 0.30 | |
| DX56D+Z | 0.12 | 0.50 | 0.60 | 0.100 | 0.045 | 0.30 | |
| DX57D+Z | 0.12 | 0.50 | 0.60 | 0.100 | 0.045 | 0.30 | |
| Forcold Forming
Japanese Standard |
SGCC | 0.15 | 0.50 | 0.80 | 0.050 | 0.030 | 0.025 |
| SGCD1 SGCD2 |
0.12 0.10 |
0.50 0.50 |
0.60 0.45 |
0.040 0.030 |
0.030 0.030 |
0.025 0.025 |
|
| SGCD3 | 0.08 | 0.50 | 0.45 | 0.030 | 0.030 | 0.025 | |
| SGCD4 | 0.06 | 0.50 | 0.45 | 0.030 | 0.030 | 0.025 | |
| For Structure
Japanese Standard |
SGC340 | 0.25 | 0.50 | 1.70 | 0.200 | 0.035 | 0.025 |
| SGC400 SGC440 |
0.25 0.25 |
0.50 0.50 |
1.70 2.00 |
0.200 0.200 |
0.035 0.035 |
0.150 0.150 |
|
| SGC490 | 0.30 | 0.50 | 2.00 | 0.200 | 0.035 | 0.025 | |
| SGC510 | 0.30 | 0.50 | 2.50 | 0.200 | 0.035 | 0.025 | |
| For Structure
AISI Standard |
S220GD+Z | 0.20 | 0.60 | 0.70 | 0.100 | 0.045 | 0.025 |
| S250GD+Z | 0.20 | 0.60 | 0.70 | 0.100 | 0.045 | 0.025 | |
| S280GD+Z | 0.20 | 0.60 | 0.70 | 0.100 | 0.045 | 0.025 | |
| S320GD+Z | 0.20 | 0.60 | 0.70 | 0.100 | 0.045 | 0.025 | |
| S350GD+Z | 0.20 | 0.60 | 0.70 | 0.100 | 0.045 | 0.150 | |
| S550GD+Z | 0.20 | 0.60 | 0.70 | 0.100 | 0.045 | 0.150 |
Mechanical Properties
| Grade | Yield Strength MPa≥ | Tensile Strength MPa≥ | Elongation A%≥ |
| DX51D Z/ZM/AZ/AM | 240-380 | 270-500 | 22 |
| DX52D Z/ZM/AZ/AM | 140-300 | 270-420 | 26 |
| DX53D Z/ZM/AZ/AM | 140-260 | 270-380 | 30 |
| DX54D Z/ZM/AZ/AM | 120-220 | 260-350 | 36 |
| S220GD Z/ZM/AM | 220 | 300 | 20 |
| S250GD Z/ZM/AZ/AM | 250 | 330 | 19 |
| S280GD Z/ZM/AM | 280 | 360 | 18 |
| S300GD A/AM | 300 | 380 | 18 |
| S320GD Z/ZM/AM | 320 | 390 | 17 |
| S350GD Z/ZM/AZ/AM | 350 | 420 | 16 |
| S450GD A/AM | 450 | 480 | 15 |
| S550GD Z/ZM/AZ/AM | 550 | 550 | – |
Galvanized Surface Selection
| Zero Spangle | Minimized Spangle | Normal Spangle | Large Spangle |
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 |
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 |
| Use of The Environment | Recommended Zinc Thickness |
| Indoor Use | Z10 or Z12 (100g/㎡or 120g/㎡) |
| Suburbs | Z20 and Painting (200g/㎡) |
| Urban or Industrial Area | Z27 (270g/㎡) or G90 (US Standard) and painted |
| Coastal Area | Thicker than Z27 (270g/㎡) or G90 (US Standard) and painted |
| Punch or Deep Drawing Application | Thicker than Z27 (270grams/㎡) or G90 (US Standard) avoid coating peeling after stamping |
| Surface Treatment Type | Code | Features |
| Chromic Acid Treatment | C | Good corrosion resistance, suitable for bare state |
| Chromic Acid Treatment+Oiling | S | Good corrosion resistance |
| Phosphoric Acid Treatment (Including Sealing Treatment) | P | Have a certain corrosion resistance, good paint performance |
| Phosphoric Acid Treatment (Including Sealing Treatment)+Oiling | Q | Has a certain corrosion resistance, good paint performance, prevent rust during transportation and storage |
| Phosphoric Acid Treatment (Excluding Sealing Treatment) | T | Have a certain corrosion resistance, good paint performance |
| Phosphoric Acid Treatment (Excluding Sealing Treatment)+Oiling | V | Has a certain corrosion resistance, good paint performance, and prevent rust |
| Oiling | O | Prevent rust during transportation and storage |
| No Treatment | M | Suitable for immediate painting |
Material Comparison
| Chinese Standard | Japan Standard | European Standard |
| DX51D Z/DC51D Z (CR) | SGCC | DX51D Z |
| DX52D Z/DC52D Z | SGCD1 | DX52D With |
| DX53D Z/DC53D Z/DX54D Z/DC54D Z | SGCD2/SGCD3 | DX53D Z/DX54D Z |
| S220/250/280/320/350/550GD Z | SGC340/400/440/490/570 | S220/250/280/320/350GD Z |
| DX51D Z/DD51D Z (HR) | SGHC | DX51D Z |
Packing And Delivery
