The POSCO Quality

Electrical Galvanized Steel

Electrical galvanized steel is made by plating steel with zinc in an electrochemical manner. Plating uses pure zinc or zinc and nickel.

Quality Features

Zn Electro-Galvanized Steel Sheets

  • Workability

    Since electrical galvanized steel has a lower coating weight and has no heat-affected zones during the manufacturing process compared to GI and GA, it has the material characteristics and workability comparable to those of the base metals, that is, cold rolled (CR) or hot rolled (HR) sheets.

  • Corrosion Resistance

    Substrate steel can be protected by the sacrificial anode reactions caused by the galvanic actions of Zinc and, even if it is exposed to air, can still be protected from corrosion by a thin film formed on the surface. (Some post-coated steel sheets are used for automobiles for better anti-corrosion property.)

  • Paintability

    The steel’s flat and even surface provide good conditions for painting. Phosphate treatment improves its paint adhesion and anti-corrosion properties after painting.

  • Weldability

    Pure Zn galvanized steel has lower weldability than cold rolled steel due to a wide area of contact under pressure and inferior electrical conductivity. However, it allows for spot or seam welding if its surface condition permits and post-treatment is applied.

  • Welding Current

    가압력변화에 따른 용접부강도 변화
  • Properties During Repeated Welding


Comparison of Anti-Corrosion Levels Between Non-Treated and Phosphate-Treated Zn-Galvanized Steels

  • White Rust Testing

  • Red Rust Testing

Zn-Ni Alloy Coated Steel

This product has been developed in order to improve the anti-corrosion durability (and prevent the through-hole corrosion) against deicers (e.g., NaCl, CaCl2) for melting ice from the roads in winter. In addition, since the coated layer of the product is solid and has a higher melting point than those of other plated layers by adding some Ni, the layer does not easily soften or melt as a Pure Zn coated layer does. The steel also allows for welding at a lower current than pure Zn galvanized steel and has a superior corrosion resistance over a long period of time.

  • Comparison of Corrosion Resistance Between Pure Zn and Zn-Ni

  • Comparison of Weldability Between Pure Zn and Zn-Ni

Types of Surface-Treated Products

  • Structure of Coated Film

    Cr6+, Cr3+/CrO3, resins and others were coated in order to improve the anti-corrosion and paint adhesion properties after Zn & alloy plating.

  • After Improvement

    Some other chemicals having properties similar to chrome are applied.An example can be an organic-inorganic polymeric composite (containing some additives).

Post-Treatment Code

후처리제품 별 후처리 Code, Full Name, 품질특성 정보
Category Post-Treatment Code Full Name Quality Features
Not-treated XX - -
Phosphate PL Phosphate Light Paintability
PM Phosphate Metallic Printability, corrosion resistance, workability
Anti-fingerprinting AG Antifinger General Anti-fingerprinting, corrosion resistance, conductivity
AL Antifinger Lubricant Anti-fingerprinting, corrosion resistance, resistance to blackening-after-processing
AC Antifinger Conductivity Anti-fingerprinting, corrosion resistance, conductivity
AF Antifinger Formability Anti-fingerprinting, corrosion resistance, workability
Black resin BT, BL - -
Fuel tanks GX - Solvent resistance, weldability, paintability

Quality Features by Product

Category Post-Treatment Code Coating Layer Structure Characteristics Common Uses Site of Manufacturing
Pure-Zn EG non-treated steel XX
Corrosion resistance,
smooth surface
Color steel sheets, home appliances/ furniture Yangso
Phosphate treated steel PL(PP)
Coating adhesion For the painting of separate parts,
home appliance
Fingerprint-resistant steel sheets AG/AL
Corrosion resistance,
TV parts,
computer parts
(for deep drawing
Conductivity Office automation Yangso
Black resin steel sheet BT
Corrosion resistance,
coating adhesion,
Outer panels of video appliances Pohang
Zn-Ni Not-treated XX
Raw corrosion resistance,
Home appliances and automobiles,
Fuel tanks GX
Gasoline resistance,
corrosion resistance
Auto fuel tank,
radiator support