Galvanized sheet: the "economical choice" in the field of rust prevention

Galvanized steel sheet uses a cold-rolled or hot-rolled steel substrate with a zinc layer applied via hot-dip or electroplating. With the combined advantages of "steel strength + zinc rust resistance," it offers a lower cost than stainless steel. It has become a mainstream material for rust prevention in sectors such as construction, home appliances, and automobiles, addressing the rust problem of carbon steel.

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I. Definition of Galvanized Steel Sheet

The core structure consists of a "base steel sheet + zinc layer." The zinc layer provides sacrificial anodic protection (zinc corrodes preferentially) or forms an oxide film, insulating against air and moisture, enhancing rust resistance. Compared to stainless steel, its cost is only 1/2-2/3. Global galvanized steel production accounts for over 30% of total sheet production, making it a "low-cost, general-purpose, rust-resistant sheet."

II. Classification of Galvanized Sheet (by Process + Zinc Layer)

1. Classification by Galvanizing Process

Hot-dip galvanized sheet (GI): The steel sheet is immersed in molten zinc (approximately 450°C). The resulting zinc layer is thick (50-200g/㎡), has strong adhesion, and offers excellent corrosion resistance. It is used in outdoor structures (such as color-coated steel tiles) and automotive chassis, with a service life of 5-15 years.

Electrogalvanized sheet (EG): The zinc layer is deposited through electrolysis. The resulting zinc layer is thin (5-50g/㎡), smooth, and highly precise. It is used for appliance housings (such as refrigerator side panels) and precision parts, and requires painting to enhance corrosion resistance.

2. Classification by Zinc Layer Type

Pure zinc galvanized sheet: An ordinary zinc layer suitable for neutral environments (such as indoor appliances).

Galvanized alloyed sheet (GA): The zinc layer forms a zinc-iron alloy with iron, offering excellent weldability and scratch resistance. It is specifically used for automotive bodies (such as doors and hoods) and is suitable for high-temperature painting processes.

III. Core Characteristics of Galvanized Sheet

Balanced Rust Resistance: The zinc layer effectively isolates corrosion. Hot-dip galvanized sheet can withstand rust for 5-10 years outdoors. Electro-galvanized sheet, when combined with paint, has corrosion resistance approaching that of stainless steel.

Significant Cost Advantage: The price is only 1/2-2/3 that of stainless steel, and compared to painted carbon steel, it eliminates the need for a secondary coating, resulting in a 20%-30% reduction in overall costs.

Excellent Processability: Suitable for stamping, bending, and welding, hot-dip galvanized sheet is suitable for building component processing, while electro-galvanized sheet meets the precision forming requirements of home appliances (such as complex curved housings).

Easy Recycling: The base steel sheet is recycled along with the zinc layer, allowing it to be separated and reused during re-refining. The global recycling rate for galvanized sheet exceeds 80%, aligning with green trends.

IV. Core Applications of Galvanized Sheet

Construction and Infrastructure: Hot-dip galvanized sheet is used to make color-coated steel tiles (factory roofs), guardrails (highway guardrails), and ventilation ducts, providing resistance to outdoor wind and rain corrosion. Alloyed galvanized sheet is used to make steel structural connectors, improving welding stability.

Home Appliance Manufacturing: Electro-galvanized sheet is used to make refrigerator side panels, washing machine housings, and air conditioner exterior casings, offering a smooth and easy-to-spray finish. Hot-dip galvanized sheet is used to make water heater linings (with enamel), providing resistance to hot water corrosion.

Automobile and Transportation: Alloyed galvanized sheet is used to make automotive body panels (doors and roofs), offering scratch resistance and weldability. Hot-dip galvanized sheet is used to make truck beds and wheel hubcaps, providing resistance to road rust.

Consumer Life and Packaging: Electro-galvanized sheet is used to make food cans (such as tins) and filing cabinets. Hot-dip galvanized sheet is used to make agricultural machinery housings (tractor cabs), resistant to humid field conditions.
V. Future Trends in Galvanized Sheet Metal

Higher Corrosion Resistance: Developing high-zinc hot-dip galvanized sheet metal (zinc layer ≥ 200g/㎡), extending its outdoor service life to 20 years; developing zinc-aluminum-magnesium alloy-coated sheet metal, with corrosion resistance 3-5 times greater than pure zinc sheet metal, enabling it to replace some stainless steel sheets.

Thinness and High Precision: Producing ultra-thin 0.15mm electrogalvanized sheet metal for micro-home appliances (such as small air purifier housings); improving sheet shape accuracy (flatness error ≤ 0.5mm/m) to meet the requirements of automotive precision stamping.

Environmentally Friendly Process Upgrades: Promoting chromium-free passivation treatment (replacing traditional chromate passivation) to reduce heavy metal pollution; optimizing the hot-dip galvanizing process to reduce zinc and energy consumption, reducing energy consumption per ton of galvanized sheet metal by over 15%.

Conclusion
Galvanized sheet metal, with its "low cost and balanced rust protection," has become an economical choice for rust prevention in the construction, home appliance, and automotive sectors. In the future, through high-corrosion-resistant coatings, high-precision processing, and environmentally friendly process upgrades, the application boundaries will be further expanded, and it will continue to replace carbon steel plates and some stainless steel plates in mid- and low-end rust prevention scenarios.

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