International Journal of Civil & Structural Engineering
Author(s) : D. GUERGOVA , D. STOYCHEV , N. BOSHKOVA , ROUMEN IANKOV , SABINA CHERNEVA
The protective Zn coatings on steel substrates are preferable because the zinc layers play a role of â€œsacrificial coatingsâ€ due to their more negative electrode potential compared to steel substrate. Besides, their protective ability strongly depends from aggressive nature of environment, which determines the need of additional efforts. Vastly improvement of the chemical stability and protective ability of the Zn coatings give the additional treatments aiming the formation of â€œfinishingâ€œ conversion layer with desired chemical-resistant composition on the Zn surface influencing against corrosion attack. Having in mind the chemical nature of the conversion layers, it is possible to predict the improvement of the chemical and mechanical properties of the system â€œConversion layerâ€/â€Zinc coatingâ€/â€Steel substrateâ€. The present study shows the results obtained concerning the indentation modulus and indentation hardness of the Cr III conversion layers and their dependence in the depth of indentation for the studied systems.The thickness of the steel substrate, protective Zn coating and finishing conversion layer are 820, 5 and 0,15 Î¼m, respectively. It was established that the system â€œConversion layerâ€/â€Zinc coatingâ€/â€Steel substrateâ€ is characterized with higher indentation hardness and modulus than the system â€Zinc coatingâ€/â€Steel substrateâ€, which improves their wear resistance and corrosion protection.