Electrogalvanized (EG) Steel

Production Process:

Electrolytic Galvanizing: A zinc layer is electroplated onto steel (typically cold-rolled coils/sheets) via an electrochemical process.

Key Steps:

Surface cleaning → Electroplating in zinc electrolyte → Passivation (optional) → Drying.

Characteristics:

Uniform Coating: Thin, precise zinc layer (typically 3–20 µm) with excellent adhesion.

Material Integrity: Retains base metal’s mechanical properties (e.g., formability of SPCC/SPCE).

Naming Convention:

Base steel grades (e.g., SPCC) become SECC (EG) after galvanizing.

Variants: SECD (drawing grade), SECE (deep drawing), SECF (structural).

Applications:

Automotive panels, electronics housings, appliances (cut/slit into custom shapes).

Aluminum-Zinc (55% Al-Zn) Coated Steel

Production Process:

Uncoiling & Cleaning: Remove oils/oxides.

Annealing: Restore ductility in reducing atmosphere.

Coating: Immersion in molten 55% Al-43.4% Zn-1.6% Si bath (~600°C).

Cooling & Air Knife: Controls coating thickness.

Post-Treatment: Chromate/paint for enhanced corrosion resistance.

 Why Choose Al-Zn Over EG?

Longer Lifespan: Al₂O₃ layer offers durable corrosion protection.

Energy Efficiency: Superior heat reflectivity reduces cooling costs.

Economic: Thinner coatings achieve equivalent coverage to Zn.

For harsh environments (e.g., coastal or industrial zones), Al-Zn outperforms traditional galvanized or EG steel. However, EG is preferred for precision components requiring tight tolerances.