Change of Mechanical Properties of Zinc Coatings After Heat Treatment

Hot-dip galvanized coatings represent a protection based on passivation of the single zinc layer. It is one of the most commonly used surface treatments of steel. However, pure zinc forms merely an insignificant upper layer. Coating crosscut is formed by intermetallic phases that can cause decrease in the level of anticorrosion protection. This results from an iron diffusion from the base material. Goal of this paper is to analyse the changes in the mechanical properties of these phases in relation to zinc coating heat treatment. For the experiment, annealing temperatures of 200 °C and 300 °C were used, and the staying time was set at 1, 3 and 5 hours. Furthermore, samples without any heat treatment were subjected to comparison as well. Moreover, following tests were conducted: bending test in compliance with the ČSN EN ISO 1519 standard, and tearing test (in accordance with the ČSN EN ISO 4624 standard). On the basis of performed tests, the changes in mechanical properties of the zinc coating after heat treatment could be analysed.