For automotive and building industry, steel with various metallic coatings is profiled. Additionally, profiles are used in soils, e.g. as carrier for photovoltaic modules or in viticulture, more general in fruit growing, to support plants under heavy fruit loads as well as during windy conditions. In fruit growing, profiles made of hot-dip galvanised steel are increasingly replacing wood based models. Therefore, an increasing importance concerning the corrosion research of hot-dip galvanized steel in soil arises/arose. It is shown the influences of chosen soil components and of substances used in viticulture on the corrosion performance of cold- rolled hot-dip galvanised steel. Specimens coated with Zn, Zn-Al-Mg and Zn-Al alloys were exposed to model soil (sand) mixed with other soil components. Additionally, the model soil was mixed with substances used in vineyards, such as fertiliser, fungicide or CuSO4 . It was found that an accumulation of CuSO4 and NH4NO3 increases the corrosion rate considerably. In addition, it is shown that in nearly all tested soils, alloy coated steel (Zn-Al-Mg and Zn-Al) has the same or lower loss of mass than conventionally hot-dip galvanised steel. Beside the laboratory exposure, electrochemical investigations are shown and corrosion mechanisms are proposed. The general mechanism consists of two parts: On the one hand general corrosion occurs which decreases with increasing depth of the soil. On the other hand, macro-cells are formed, which accelerate the corrosion rate at lower areas of the specimens. Furthermore, mechanisms concerning the corrosion promoting effect of CuSO4 and NH4NO3 are proposed. The results of these studies allow a better understanding of the corrosion processes of hot-dip galvanised steels in soil and represent a basis for further work as well as for interpretation and prediction of corrosion damages in soils.
|Translated title of the contribution
|Corrosion of hot-dip galvanised steels in soils
|Published - 2018
Bibliographical noteembargoed until 29-01-2023
- hot-dip galvanised
- loss of mass