Influence of thickness of intermetallic layers on fracture resistance of galvanized coatings

Galvanized coatings, commonly used for corrosion protection of steels' surfaces, are susceptible to crack formation and propagation due to thermal stress and deformation from post-processing. To identify geometrical parameters governing crack propagation of the coating layers, mechanics of crack propagation is numerically analyzed using finite element simulations. Focuses are given to addressing the influence of the coating thickness on fracture resistance of the zinc–iron intermetallic layers of galvanized coatings that are subjected to four-point bending. The study demonstrates that a decrease of the delta phase layer with respect to the zeta phase layer improves crack resistance of the coating layers. Furthermore, increasing the thickness of eta phase layer is shown useful for retarding crack growth in the intermetallic layers. Galvanizing protocols may be tailored to achieve a combination of intermetallic layer thicknesses that enhances the coatings' crack resistance.

► Influence of coating thickness on fracture resistance of galvanized coatings is investigated.
► Through-cracks in galvanized coatings are induced by thermal stress and bending loads.
► Decrease of delta phase with respect to zeta phase improves fracture resistance.
► Enlarging eta layer suppresses crack growth in intermetallic layers.