Differences in Production Process
Cold rolled steel (CRS) uses hot rolled coils as material. It is obtained by continuous rolling at room temperature (under recrystallization temperature) after pickling to remove the oxide scale. Due to the cold hardening caused by continuous cold deformation, the strength and hardness of the coil rolled steel increase, and the toughness and plasticity decrease. While galvanized steel (GI) often uses cold rolled steel or hot rolled steel sheets as base metal, then a layer of zinc is applied on the surface by hot-dip galvanizing or electro-galvanizing to enhance the corrosion performance of the base metal.
Different Anti-Corrosion Performance
As mentioned above, the galvanized steel is protected with a layer of zinc coating. So it has better corrosion resistance than cold rolled steel. Accordingly, a GI steel product has a longer lifespan than a CR steel product under the same circumstance.
Mechanical Property Difference
In fact, the zinc layer on the GI surface will not change the mechanical properties of the substrate. The mechanical properties of cold-rolled steel and GI steel are very similar. Therefore, they can be cut, punched, welded, and processed. But the ductility and weldability of cold rolled steel are better than that of galvanized steel. Below is a table showing their mechanical properties.
| Material Grades | Cold Rolled Steel | Hot Dipped Galvanized Steel | Mechanical Properties |
| High Strength | G550 | G550 | Tensile strength ≥570MPa Yield strength ≥550MPa |
| Deep Drawing | SPCESPCEN | SGCE/DX52D/53D | Tensile strength≥260MPa Yield strength: 180-260MPa Elongation: 36-38% |
| General Use | SPCC | SGCC/DX51D | Tensile strength ≥270MPa Yield strength ≥280MPa Elongation: 22-36% |
Steel Surface
When it comes to appearance, they seem to be similar to some extent, but still have some distinctions. For example, the cold rolled steel has a clean, smooth, and glossy surface, with high precise and close tolerance. It is very similar to electro galvanized steel. As for hot-dipped galvanized steel, it is rough, rugged, dark, and has spangles, including common spangles, big spangles, small spangles, and zero spangles.
In addition, both cold rolled and galvanized steel can be painted to enhance the overall look.
Hot Dipped Galvanized Steel Coil
