08F galvanized steel pairs an ultra-low-carbon rimmed-steel substrate with a zinc or zinc-alloy coating. The very low carbon content and tightly controlled silicon level give the base metal excellent ductility, while the coating provides both barrier and sacrificial protection against corrosion. The result is a sheet that can be deep drawn, bent and welded into complex shapes and still withstand humid, coastal or mildly aggressive service conditions.
What Is 08F Galvanized Steel?
08F is an ultra-low-carbon grade in the Chinese national carbon-steel system. The "F" suffix denotes a rimmed (boiling) steel, meaning the melt is not fully deoxidised, which keeps carbon and silicon at very low levels and produces a soft, highly formable sheet. Sheet and strip of this grade are covered by standards such as GB/T 710 for hot-rolled product and GB/T 13237 for cold-rolled product, while the coating itself follows continuously hot-dip zinc-coated sheet standards such as GB/T 2518 or ASTM A653.
Because the substrate is soft and clean, 08F is routinely galvanised in three ways: hot-dip zinc coating (SGCC type), electro-galvanised zinc coating (SECC type), and 55% aluminium-zinc alloy coating, often called aluzinc. Hot-dip coating gives the heaviest, most economical barrier for outdoor parts, electro-galvanising gives a very smooth surface for painting and appearance parts, and aluminium-zinc coating gives the best long-term corrosion resistance in marine or industrial atmospheres.
Chemical Composition of 08F
The chemistry is deliberately lean. Low carbon keeps the ferrite soft; low silicon prevents excessive growth and brittleness of the iron-zinc alloy layer during hot-dip galvanising; manganese adds a modest amount of strength without hurting ductility.
| Element | Typical content | Function |
|---|---|---|
| Carbon (C) | 0.05–0.11% | Ultra-low carbon for maximum cold formability and weldability |
| Manganese (Mn) | 0.25–0.50% | Raises strength slightly without reducing plasticity |
| Silicon (Si) | ≤0.03% | Limits brittleness of the zinc-iron alloy layer during hot-dip coating |
| Phosphorus (P) | ≤0.035% | Residual element controlled for ductility |
| Sulphur (S) | ≤0.035% | Residual element controlled for forming and welding |
Mechanical and Forming Properties
The annealed sheet is defined chiefly by its yield strength and elongation, which together allow severe forming operations such as deep drawing and stretch forming without tearing.
Yield strength (Rel): ≥175 MPa for sheet thickness ≤16 mm
Elongation: ≥35% (tensile test with an 80 mm gauge length)
Hardness: ≤131 HBW in the as-supplied condition
Minimum bending radius: 1.0t (t = sheet thickness), far better than Q195 galvanised sheet
Magnetic behaviour: high permeability and low remanence after annealing, which suits electromagnetic shielding parts
Two process points matter in practice. First, deep-drawing performance depends on grain size and texture, so 08F is normally supplied annealed and skin-passed to a controlled surface roughness. Second, because the steel is rimmed rather than fully killed, the surface quality of the substrate is high, which means the sheet can be painted or electroplated directly after galvanising, with no extra grinding or phosphating step.
Coating Options and Service Environment
| Coating | Designation type | Best suited to |
|---|---|---|
| Hot-dip zinc | SGCC type, GB/T 2518 / ASTM A653 | General outdoor parts, heavy zinc mass such as ≥275 g/m² for coastal areas |
| Electro-galvanised zinc | SECC type | Appearance and paint-critical parts such as computer cases and appliance shells |
| 55% aluminium-zinc | Aluzinc, ASTM A792 / GB/T 14978 | Long-life roofing, cladding and high-corrosion environments |
For coastal or high salt-fog service, specify a hot-dip coating of at least 275 g/m² or move to aluminium-zinc coated sheet, which extends coating life several times over plain zinc at the same mass. For elevated-temperature duties such as boiler casings and chimney sections, the zinc coating should not be the only protection: performance falls away as temperature rises, so heavier alloy or aluminium-zinc systems, or a change of substrate, are the safer choice. Selection should always be made against the actual temperature and atmosphere of the application rather than a generic corrosion class.
Typical Applications
Automotive
Door inner panels and engine hoods, where high plasticity and surface quality are decisive
Instrument panel brackets and air-conditioning vents, which need precise forming and fingerprint resistance
Home appliances and consumer electronics
Refrigerator side panels and computer enclosures
Electro-galvanised (SECC) substrate accept polyester paint directly, cutting finishing cost
Microwave-oven cavities and transformer housings, using the permeability and low-remanence behaviour
Precision hardware and instruments
Dials and housings where the hot-dip layer must give long protection while surface accuracy is retained
Small brackets and covers produced by progressive-die stamping
08F Versus Q195 Galvanised Steel
| Item | 08F galvanised | Q195 galvanised |
|---|---|---|
| Carbon level | Very low, tightly controlled | Higher and broader |
| Deep-drawing performance | Excellent; complex automotive and appliance panels | Good for moderate forming only |
| Substrate surface | Higher flatness; paint or plating applied directly | Often needs grinding or phosphating first |
| Best use | Complex, visible, form-critical parts | Structural and general-purpose parts |
In short, choose 08F when the part is deep drawn, painted as a visible surface, or used for magnetic shielding. Choose Q195 when the part is simple, structural and cost-driven.
Frequently Asked Questions
Q: What does the 08F designation mean?
It is an ultra-low-carbon rimmed steel grade. The number refers to the very low carbon level and the "F" indicates rimmed (boiling) steel, which is why the sheet is so soft and formable.
Q: Is 08F galvanised steel suitable for deep drawing?
Yes. With a yield strength of at least 175 MPa, elongation of at least 35% and a minimum bending radius of 1.0t, it handles deep drawing and drawing operations that would crack harder galvanised grades.
Q: Which coating should I choose for a coastal site?
Specify a hot-dip zinc coating of at least 275 g/m² or, for longer life, a 55% aluminium-zinc coated sheet, which outperforms plain zinc of the same coating mass in salt-fog exposure.
Q: Can 08F galvanised sheet be welded directly?
Yes. Spot welding and arc welding can both be used without special process adjustment, although the zinc coating should be removed from the weld zone when a fully sound weld is required.
Q: Why is low silicon important in the 08F chemistry?
Silicon accelerates growth of the brittle iron-zinc alloy layer during hot-dip galvanising. Keeping it at or below 0.03% preserves coating adhesion and ductility when the sheet is bent or formed after coating.
Q: How does 08F compare with Q195 for appliance shells?
08F offers better formability and a flatter surface, so it can be painted or electroplated directly, while Q195 usually needs additional surface preparation before painting.