Difference Between Hot-Dip and Cold Galvanized Seamless Pipes
Post Overview
Difference Between Hot-Dip and Cold Galvanized Seamless Pipes
Hot-Dip Galvanized Seamless Pipe:
The pipe substrate undergoes complex physical and chemical reactions with the molten zinc bath, forming a tightly bonded zinc-iron alloy layer with superior corrosion resistance. This alloy layer integrates seamlessly with both the pure zinc coating and the steel base, creating exceptional durability.
Cold Galvanized (Electro-Galvanized) Seamless Pipe:
The zinc coating is applied via electroplating, resulting in a distinct, non-bonded layer that sits atop the pipe substrate. The thinner zinc layer adheres weakly and is prone to peeling, offering limited corrosion protection. Note: Cold-galvanized pipes are prohibited for potable water supply in new residential constructions due to these shortcomings.
Key Contrasts:
| Feature | Hot-Dip Galvanized | Cold Galvanized |
|---|---|---|
| Coating Formation | Metallurgical alloy layer | Electroplated layer |
| Adhesion | Integral bond (Non-peeling) | Weak mechanical adhesion |
| Thickness | Thicker (50–200 μm) | Thinner (5–30 μm) |
| Corrosion Resistance | High (2–5× bare steel) | Low (Prone to rust) |
| Applications | Outdoor, harsh environments | Indoor, non-critical uses (banned for water supply) |
