Precautions for Using Galvanized(GI) Pipe

Galvanized pipe (GI Pipe) is widely used in construction, water supply, gas, and other fields due to its rust-resistant zinc coating. However, improper use can lead to problems such as zinc coating damage, pipe corrosion, and insufficient pressure bearing capacity. The following are key precautions for GI pipe handling:

Characteristics of Galvanized Pipe:

Galvanized pipe is a type of steel pipe coated with zinc. It offers corrosion and wear resistance and is widely used in construction, manufacturing, and other fields. Galvanized pipe is available in two types: hot-dip galvanizing and cold-dip galvanizing. Hot-dip galvanizing offers a bright surface and excellent corrosion resistance, but is more expensive. Cold-dip galvanizing offers a rougher surface but is relatively cheaper.

Precautions for Using Galvanized Pipe:

1. Material Inspection: Before using galvanized pipe, inspect the surface for rust, cracks, and other issues to prevent them from affecting performance.

2. Prevent Collisions: Galvanized pipes must be protected from collisions during transportation, handling, and installation to prevent surface damage. 3. Maintaining Unobstructed Access: When using galvanized pipes, be sure to check for obstructions and clean them regularly to maintain unobstructed access.
4. Avoid Overloading: Galvanized pipes have limited load-bearing capacity, so avoid overloading during use to prevent safety hazards.
5. Anti-Corrosion Measures: Although galvanized pipes are corrosion-resistant, appropriate anti-corrosion measures are still required in some special environments, such as the ocean and acid rain.

Installation Environment and Pretreatment:

1. Avoid Acidic or Humid Environments: The zinc coating is susceptible to corrosion in environments with a pH below 6 or above 12. If installation is necessary, apply an additional anti-corrosion coating.
2. Clean Surface Impurities: Before installation, use a dry cloth to remove oil and dust from the pipe wall to prevent the zinc coating from losing adhesion.
3. Avoid Direct Contact with Copper Pipes: Copper ions accelerate electrolytic corrosion of zinc, so insulation is required.

Processing and Connection Specifications:

1. Cutting and Welding
- Use a dedicated galvanized pipe cutting machine when cutting to avoid high temperatures that could damage the zinc coating. Deburr any hand sawing with a file.
- Welding temperatures must be kept below 200°C (refer to AWS D1.1). Above this temperature, the zinc coating will evaporate and produce toxic fumes, so ventilation is required.

2. Threaded Connections
- Apply zinc-based sealant to the threads to prevent leakage. Do not use raw tape, as it may damage the seal of the galvanized coating.

In-Service Maintenance and Inspection:

1. Regular Corrosion Inspection
Inspect the pipe surface every six months. If white rust (zinc oxidation products) is present, clean it with a weak alkaline solution (such as 5% sodium carbonate). Red rust (iron rust) requires local zinc refilling or pipe replacement.

2. Pressure and Temperature Limitations
- The operating pressure of ordinary galvanized pipe is ≤1.6MPa. In high-temperature environments (>60°C), the pressure capacity decreases by 30%. Thickened or seamless galvanized pipe should be used.

Notes for Special Scenarios:

1. Underground Installation: Requires wrapping with PE anti-corrosion tape and a minimum burial depth of 0.8 meters to prevent freezing or mechanical damage.
2. Drinking Water System: Newly installed pipes must be flushed with clean water for at least 48 hours to ensure zinc residue is less than 1.5mg/L.

These measures can significantly extend the service life and safety of galvanized pipes. For further selection or installation guidance, it is recommended to consult a professional piping engineer.

Read more: MS and GI Pipe Difference or Guide for selecting the thickness of galvanized steel pipe