Short answer: Galvannealed (GA) steel is hot-dip galvanized sheet passed through an annealing furnace so the zinc alloys with iron into a matte Zn-Fe layer; it paints and spot-welds far better than plain galvanized steel but has slightly lower bare-metal corrosion life, which is why it dominates painted automotive and appliance panels.
At a Glance
How Galvannealing Works
The strip leaves the zinc pot and immediately enters an in-line furnace at roughly 500–565 °C. Iron diffuses out of the steel into the molten zinc, converting the coating into gamma, delta and zeta Zn-Fe phases with about 8–12% iron. The result is designated A (ASTM A653 coating type) rather than G, and the coating is fully alloyed rather than free zinc — the plain-galvanizing route it branches from is described in Hot Dip Galvanizing Process and the product family in Galvanized Sheet Guide and our Galvanized Steel Supplier programme.
Why Fabricators Choose GA
Three practical wins. Paint — the matte crystalline surface anchors e-coat and powder without the phosphating that bright Galvanized Sheet Guide product needs, and it will not exhibit spangle telegraphing through topcoat; see Anodizing Vs Powder Coating for the coating comparison. Lassen — the higher-melting alloy layer reduces electrode pick-up, so spot-weld electrode life is markedly longer than on GI. Formability of the paint system — the coating stays put on mild bends, though it is more brittle than free zinc and can powder on severe draws, so tooling should be reviewed against the parts made by our Metal Stamping Supplier team.
Limits, Grades & Specification
Bare GA corrodes faster than GI of the same coating weight because there is no free zinc reservoir, so GA is specified where the part will be painted — unpainted roofing and outdoor structures should stay GI, or move to Galvalume Vs Galvanized Steel coatings. Order by ASTM A653 (or JIS G3302 / EN 10346 equivalents, cross-referenced in Jis Steel Equivalent), stating coating designation such as A40 or ZF100, steel grade (CS Type B, HSLA 340), thickness and temper. Comparative corrosion planning is in Zinc Plating Vs Galvanizing en How To Prevent Metal Rust, with mill documentation per Mill Test Certificate Guide.
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Veelgestelde vragen
Galvannealed steel is hot-dip galvanized sheet that has been annealed in-line so the zinc coating alloys with iron into a matte Zn-Fe layer containing roughly 8–12% iron.
Galvanized steel has a bright free-zinc coating with better bare corrosion life; galvannealed has an alloyed matte Zn-Fe coating with far better paint adhesion and spot weldability.
It accepts e-coat and powder directly without phosphating in most cases, though a primer is still used where the topcoat system requires it.
Yes. HXSCO supplies galvannealed (ASTM A653 Type A / ZF) coil and sheet in CS and HSLA grades with the coating weight and thickness you specify.
Order Galvannealed Steel
HXSCO supplies galvannealed (GA) coil and sheet to ASTM A653, JIS G3302 and EN 10346 in CS and HSLA grades. Send thickness, coating weight and tonnage for a quote.