Comprehensive analysis of the causes of zinc coating degradation on cold-formed steel profiles for construction applications
DOI:
https://doi.org/10.37142/2076-2151/2025-1(54)156Keywords:
galvanized steel, cold-formed profile, cold rolling, hot-dip galvanizing, passivation, chlorides, corrosion, roll-forming technology, chemical analysis.Abstract
Kukhar V., Kurpe O., Butenko E., Tsymidanov D., Malii Kh., Spichak O. Comprehensive analysis of the causes of zinc coating degradation on cold-formed steel profiles for construction applications
This article presents a comprehensive analysis of the causes behind zinc coating degradation observed on cold-formed galvanized steel profiles used in construction. The profiles were manufactured from steel grade DX51D+Z140, widely applied in structural elements such as window reinforcements, frames, and façade systems. The study investigates the entire technological chain — from hot-rolled coil pickling and cold rolling, through hot-dip galvanizing in protective atmospheres, to final roll-forming operations on multi-stand lines. Each stage is evaluated for its potential contribution to defects, especially with regard to corrosion resistance. Key technological factors contributing to premature corrosion include incomplete removal of iron oxides during acid pickling, insufficient surface passivation after galvanizing, and contamination by chloride-bearing substances — likely from external environmental sources or technical water. The research involved experimental thickness measurements of the zinc coating on both flat sheets and finished profiles using non-destructive magnetic methods, followed by statistical evaluation applying Cochran's and Fisher's criteria for reproducibility and adequacy. Additionally, chemical analyses were conducted to identify surface and sub-coating contamination by chlorides (Cl⁻), sulphates (SO₄²⁻), hexavalent chromium (Cr(VI)), and organic residues from emulsions. The results confirmed that although the average coating thickness generally complies with the Z140 standard (DSTU EN 10346:2014), localized inconsistencies and technological lapses can lead to the emergence of "white rust" before installation. The findings emphasize the importance of improving not only galvanizing and roll-forming operations but also storage and transport conditions. Recommendations are provided to optimize industrial practices and enhance the durability of zinc-coated steel profiles under real-world conditions.
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