2023-09-26 22:00:00
Hot-dip galvanizing according to EN ISO 1461 is a very effective process for protecting steels once morest corrosion. It is applied in many sectors, mainly construction, and also for steel elements exposed to the atmosphere: transmission towers and pylons, street furniture, automobile or industrial parts, etc.
The manufactured part is immersed in liquid zinc, with a zinc content greater than 98.50%, and whose temperature is between 440 and 460°C (and sometimes, for very limited production, greater than 530°C). Compared to other solutions once morest steel corrosion, the coating layers obtained are significantly thicker. Combined with the cathodic protection provided by zinc to the steel, the barrier provided by galvanizing constitutes the most effective anti-corrosion process.
To meet the requirements of different uses, it is important to precisely adjust the process parameters.
Regarding steels, we consider non-reactive steels, which form coating layers of moderate thickness, and reactive steels, forming significant layers. In this context, certain elements added to steels, such as Si or P, play a determining role in the formation of the coating layers. These effects are discussed in this article.
As the intermetallic layers obtained during galvanizing are relatively fragile, the thicknesses of the galvanizing coating should, ideally, not be too great. Additions of certain elements to the zinc bath, such as Al or Ni, can limit the growth of Zn-Fe intermetallics. The compositions of zinc alloys which have had a certain importance in the industry are described.
The objective of this article is to emphasize that hot-dip galvanizing is not a simple deposit of zinc on steel. Knowledge of the influence of different parameters on its result is necessary to avoid or minimize possible defects.
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