The Role of Particle Size and Shape in the Fracture Resistance of Anti-Corrosion Coatings for Steels

摘要

Model results are presented quantifying the role of brittle particle size and shape on coating fracture resistance. Although the results can be applied to a broad range of heterogeneous coating systems, the motivation for this work is enhancing the strain tolerance of GALVALUME coated sheet steel, which uses a zinc-aluminum-silicon alloy coating to prevent the corrosion of the steel sheet, primarily in architectural applications. For these applications coated sheets are typically subjected to roll-forming processes that introduce bends to increase the stiffness of the architectural panels. Tensile strain-induced cracking from the roll-forming process can lead to tension bend staining (TBS), in which cosmetic corrosion of cracked regions of the coating can cause staining of the architectural panels. SEM observations of sectioned strained specimens are presented, showing that coating fracture initiates from the fracture of brittle Si particles within the coating matrix. Finite element models are used to quantify the effect of particle size and particle shape on the average energy release rate for cracking through a particle. It is shown that spherical particles are the worst particle shape for inhibiting particle fracture.