Galvanneal vs aço galvanizado: as diferenças explicadas

Galvanneal vs Galvanized Steel: The Differences Explained

What is electrogalvanization?

The corrosion rate of galvanized pipes is largely influenced by factors such as the galvanizing method, the thickness of the galvanized layer, the amount of galvanizing and the environment in which the pipes are used.

Cold galvanized pipes are particularly susceptible to corrosion. They have low galvanization, with only the outside of the steel tube being coated, leaving the inside exposed. With an average of just 20g/ m2 of zinc on one side, these pipes are prone to rust.

Under normal conditions, cold galvanized steel pipes are expected to start rusting within a year. The rusting time can be prolonged by increasing the thickness of the galvanized layer. For example, pipes with a thickness of less than 2.75 mm can take 2 to 3 years to start rusting, while those with a thickness of 3.0 mm or more can last 3 to 5 years before rust begins.

How to remove rust from galvanized pipes?

If a galvanized pipe becomes rusty, it can be treated to remove the rust. The following are the main methods for removing rust from galvanized pipes:

  • First, the surface of the steel pipe is cleaned with solvent to remove any organic matter present on the surface.
  • Then wire brush or other tools are used to remove loose or flaky rust and welding slag.
  • After pickling, the rust on the galvanized pipe is almost completely removed.

Do galvanized steel pipes need to be painted with anti-rust paint?

After the steel pipe is galvanized, its surface is coated with a layer of zinc, which acts as a barrier between the steel pipe and the atmosphere. This prevents direct contact between the atmosphere and the steel pipe and protects it from corrosion.

The zinc coating on the surface of the steel pipe is highly reactive, and at normal temperatures, a thin, dense layer of zinc carbonate is formed in the air to protect the zinc from oxidation.

As a result, the galvanized pipe is protected from rust and does not require painting with anti-rust paint, either on the zinc coating or on the steel pipe itself.

However, if the zinc coating is damaged (for example, when the steel pipe is welded and the coating at the joint burns), the steel pipe is exposed to air and loses the protection of the zinc coating. In this case it must be repainted with anti-rust paint.

The galvanized layer of galvanized steel pipe has anti-rust properties and is normally connected using threads.

In general, it is not necessary to paint with anti-rust paint unless unconventional connection methods such as welding are used. If the galvanized layer is damaged, the affected area must be painted with anti-rust paint.

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