3 Best Ways to Weld Large and Small Diameter Galvanized Pipes

Galvanized steel pipe is a common and popular type of rolled metal. Therefore, the question of choosing a method for welding such pipes always remains relevant. Let's look at three popular and practical ways to weld galvanized pipes of different diameters.

#1 Electric Welding

One of the most common methods is electric welding. It consists in heating the working surface up to 1200 C*. The boiling point of zinc is 906 degrees. Therefore, before starting work, the welding spots are cleaned. Otherwise, the protective coating burns out, which can lead to a number of negative consequences:

• First and foremost - harm to health. Vapors of zinc can cause a number of dangerous reactions in humans up to respiratory arrest. Therefore, it is important to protect the face and respiratory organs with a special respirator, as well as wear rubberized gloves with a thermal insulating layer.
• Due to damage to the zinc coating at the joint, corrosion processes can begin prematurely, with a significant reduction in the shelf life of the product.
• Zinc evaporation causes pores and cracks to appear on the surface of the pipe. As a result, the tightness of the weld can be broken.

To avoid these undesirable effects, electric flux welding is used.

#2 Electric welding with flux

There is no need to remove the zinc coating with this method. The technology is also suitable for the installation of plumbing systems.

The product edge is cleaned and degreased. It is important to process not only the outer, but also the inner surface. Then the parts are heated by 20-30 cm in length.

Welding quality is significantly affected by nozzle size. For example, to weld a pipe with a large cross section (more than 250 mm) and a wall thickness of more than 2-6 mm, a torch with a 2-4 mm nozzle is needed. Too large a nozzle diameter can lead to excessive heating and evaporation of the protective layer. On the contrary, a small diameter nozzle will cause the solder to stick.

Soldering is done with an oxy-acetylene flame corrected for excess oxygen. Joining rolled products with a large diameter requires multi-pass welding.

Method Benefits:

• excellent weld penetration;
• suitable for large diameter thick-walled pipes;
• flexibility in terms of torch movement and orientation.

Full compliance with the technology guarantees a good seam and does not require additional corrosion protection.

#3 Electric arc welding

Applies to butt fillet welds. Welding requires special electrodes. The choice of electrode depends on the steel grade. Rutile-coated electrodes are suitable for galvanized pipes, because:

• titanium oxide in the composition quickly ignites the arc;
• the connection comes out tight and of high quality;
• no spatter, no metal loss.

The speed of the electrode passage has a huge impact on the quality of welding. If the speed is too low, the metal can burn through, and if the speed is too high, the seam will not have sufficient strength. After welding, an anti-corrosion compound must be applied to the seams.

Method Benefits:

• light portable equipment;
• flame control;
• low cost and maintenance

Alternative methods for joining galvanized pipes

Without heating, you can connect galvanized pipes with a threaded joint. The method is quite complicated, costly and not suitable for large diameter pipes.

When installing heat and water systems, prefabricated kits with fittings are used. The advantages of the method are a strong connection and high speed of work.