Abstract
This paper investigates the physical reasons for the apparently poor conductivity of galvanized steel plates (GSP), which has not yet received a proper explanation. Apparent conductivities as low as 0.1 MS/m were reported in the past, which are incongruously low compared to the DC conductivity of steels (4 to 8 MS/m), or zinc (16.7 MS/m), the most common coating agent used against corrosion in steel products. A comprehensive review of results from metallurgy and materials science is presented, providing insights about the multi-layered structure of zinc-based coatings. These are found to be made of a limited set of intermetallic zinc-iron compounds each characterized by a steeply decreasing conductivity as their iron percentage increases. Depending on the galvanization process the relative thickness of these layers can vary widely, explaining the seemingly random apparent conductivity of GSP. Theoretical modeling of these structures shows that their apparent conductivity scales linearly with the frequency, suggesting that it can be far lower than acknowledged so far. An extensive analysis of power-dissipation data from the literature of GSP-based reverberation chambers confirms these predictions, with multiple instances of apparent conductivities as low as 10 kS/m. The conclusion is not that GSP are hopelessly poorly conductive, but rather that care should be taken in selecting the right coating technology, not only based on corrosion protection and minimizing costs, but also in view of its impact on GSP conductivity.
Highlights
S TEEL plates find wide use as structural elements in many applications, such as in hangars, warehouses, ship hulls, cars and transportation vehicles, pipe lines and air ducts
Galvanized steel plates (GSP) used in typical reverberation chambers (RC) are zinc coated, but empirical results can be explained only by assuming that their surface conductivity be considerably lower than 1 MS/m [8], [9]
The criteria applied in selecting data published in the RC literature are explained in Section IV-B, while Section IV-C summarizes the main findings of this analysis
Summary
S TEEL plates find wide use as structural elements in many applications, such as in hangars, warehouses, ship hulls, cars and transportation vehicles, pipe lines and air ducts. Galvanized steel plates (GSP) used in typical RC are zinc coated, but empirical results can be explained only by assuming that their surface conductivity be considerably lower than 1 MS/m [8], [9] In all these previous empirical observations, no physical justification was advanced as to why GSP present such a low conductivity. In continuous galvanization small amounts (around 0.15%) of aluminum may be added to the zinc bath in order to inhibit iron diffusion, blocking the formation of the brittle ζ layer, whose poor mechanical formability would not be compatible with subsequent mechanical processing This results in considerably thinner coatings, typically between 7 and 20 μm thick but potentially less than 3 μm thick for indoor applications [13], presenting only a η layer [19]. Accurate chemical analyses of the structure of galvannealed coating have confirmed their considerable variability [29], [30]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
