​ Titanium-Plated Angle Steel: Production Processes of Hot-Dip & Electro-Galvanized Angle Steel

Titanium-Plated Angle Steel: Production Processes of Hot-Dip & Electro-Galvanized Angle Steel

1. Hot-dip galvanized angle steel, also known as hot-dipped galvanized angle steel or hot-dip zinc angle steel.

It is produced by immersing rust-removed angle steel in molten zinc liquid at around 500°C, forming a zinc layer on the steel surface for anti-corrosion purposes. It is suitable for harsh corrosive environments with strong acid, alkali mist and similar conditions.

Process flow for hot-dip galvanized angle steel: pickling of angle steel → water washing → flux dipping → drying and preheating → hot dipping → cooling → passivation → cleaning → polishing → completion of hot-dip galvanizing.

The zinc coating of hot-dip galvanized angle steel is uniform with thickness reaching 30–50μm and high reliability. The zinc coating forms a metallurgical bond with steel and becomes part of the steel surface, granting reliable long-term coating performance. Since its raw material is angle steel, its classification is consistent with that of common angle steel.

2. Electro-galvanizing process protects metal against corrosion. It adopts zinc-rich paint applied onto the substrate by any coating method. A zinc-rich film will form after drying, containing up to 95% zinc in the dry coating.

It is suitable for repair work: only damaged areas on protected steel surfaces need re-coating after surface preparation. The electro-galvanizing process is applied for corrosion protection of various steel products and structures.

Electro-galvanized paint relies mainly on electrochemical principles for corrosion prevention. Full contact between zinc powder and steel must be ensured to generate electrode potential difference, so surface preparation of steel is critical.

Before spraying electro-galvanized coating, mechanical rust removal (sandblasting, shot blasting, etc.) shall be carried out to achieve cleanliness grade ISO 8501-1 Sa 2.5, equivalent to GB 8923 Sa 2.5.

Definition: “After mechanical rust removal, the steel surface shall be free of oil, rust, scale and other contaminants, or only faint traces remain; 95% of the steel surface is impacted by steel shot/abrasive and reveals metallic luster.”

Another indicator for surface preparation quality is roughness. Different electro-galvanized materials have different roughness requirements.

In Zinga’s construction specification, the average roughness Ra=12.5μm, corresponding to Rz=55~75μm.

For Power Zinc and Robaruk, the roughness requirement is slightly lower, Rz=40~60μm.

When electro-galvanizing coating is used independently as an anti-corrosion film, surface roughness can be controlled at a slightly lower value to guarantee coating thickness.

When electro-galvanizing serves as the primer for heavy-duty anti-corrosion coatings and the total system coating thickness exceeds 180μm, steel surface roughness Rz shall be greater than 60μm to ensure adhesion of the whole coating system.