Abstract
This article deals with monitoring the corrosive degradation rate of zinc and duplex coatings, usable in technical practice as anti-corrosion protection in tanks for the transportation and application of industrial fertilizers and manure. Based on long-term results, samples of anticorrosive coatings for laboratory testing are prepared. The selected anticorrosive coatings are explicitly designed to increase the corrosion resistance of tanks with considerable corrosion load. To compare the anti-corrosion effect, standard hot-dip galvanizing and a duplex system were chosen, and a synthetic urethane alkyd coating was used as an organic substrate. The prepared samples were subjected to metallographic tests (measuring the thickness of the anticorrosive system in the longitudinal section of the sample) and evaluation of the microstructure in the hot zinc coating. However, the essential analysis is focused on corrosion degradation in the salt mist environment according to ČSN ISO 9227 (the NSS method). Based on the results of the comparison of anti-corrosion systems using the salt spray, the duplex systems demonstrated a significantly higher corrosion resistance than a single inorganic metallic coating.

Key words
hot-dip galvanizing, duplex coating, corrosion rate, protective coating thickness

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