Hot-dip galvanizing is an essential process for protecting metal structures against corrosion, increasing their durability and resistance over time.
According to Raphael Soeiro, engineering manager at Metal Light Solar, understanding the differences between post-galvanized and pre-galvanized steel is essential to ensure the useful life of structures used in solar plants.
What is hot dip galvanizing?
Hot-dip galvanizing involves immersing carbon steel, cast iron or weathering steel in molten zinc, creating a protective layer against oxidation. This process protects the parts internally and externally, ensuring greater resistance to corrosion in different environmental conditions.
Durability and material degradation rate
The longevity of metal structures is directly linked to the material's degradation rate. According to Soeiro, Metal Light equipment works with an average value of 56 µm, as indicated by ABNT NBR 6323:2016, and has an estimated useful life of 27 years in C3-classified environments.
Taking into the average annual degradation of 1,4 µm, over 27 years the accumulated loss of material reaches 37,8 µm. With an additional safety factor of 20%, the total required for complete protection of the parts reaches 45,3 µm.
The limitations of pre-galvanized steel
Although the pre-galvanizing process is similar to post-galvanizing, it occurs during the steel coil processing stage, before the parts are formed. According to the engineer, this technique presents significant challenges, as the zinc bath applied is not sufficient to form a lasting protective layer.
“The zinc layer in pre-galvanized steel does not exceed 32,41 µm (275g/m²), with an average value of 20 µm, while that required to guarantee 27 years of protection is 45,3 µm. This means that pre-galvanized structures have a limited lifespan of around 12 years, well below the ideal for solar plants,” he explained.
Another problem faced by pre-galvanized steel occurs during the forming of the parts, when there is a risk of damage to the zinc layer, further compromising its durability. This type of wear does not occur in post-galvanized steel, which already receives the zinc coating after forming, ensuring uniform protection throughout the structure.
Conclusion
The choice between post-galvanized and pre-galvanized steel has a direct impact on the durability and safety of solar plants. While post-galvanized steel meets the expected service life requirements for the industry, pre-galvanized steel has significant limitations that can compromise the long-term performance of structures.
To avoid frequent maintenance and ensure greater protection against corrosion, Metal Light Solar reinforces the importance of using suitable materials that are resistant to the environmental conditions where the plants will be installed.
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An answer
Post-dip galvanizing is really the most suitable for protecting carbon steel structures, as it guarantees a continuous layer across the entire surface. However, controlling the uniformity and micron of this layer is extremely important for the expected/projected guarantee.