No abstract

The continuous increase in demand for aluminum coatings for the automotive industry is associated with the need to improve their quality in terms of protective and mechanical properties. The aluminum coatings produced hot-dip, on the border with the steel substrate formed intermediate phases FeAl3, and Fe2Al5, which reduce the corrosion resistance and limit the possibility of forming a coated article. The paper determines the effect of the addition of 7% Si to an aluminum coating (690°C/60 s) on the microstructure thickness and type of intermediate phases as well as hardness and surface features. It has been shown that the addition of Si results in a 40 % increase in the hardness of the coating and reduce the surface roughness. In addition, is limited interdiffusion of Al and Fe, as a result of which an intermetallic phase layer is formed, Al7-9Fe2Si enriched phase, 4 times thinner than a coating without the addition of Si, while maintaining the thickness of the outer coating layer.

Protective coatings provide protection of structures against corrosion, but they also aim to meet marketing requirements – decorative qualities. One of the representatives of protective coatings are fire coatings based on Al and Al-Si, which have been used, among others, in the automotive industry. The production of Al-Si coatings using the fire method (known as: immersion) consists in immersing a previously degreased detail in a bath of molten coating metal. Al-Si coatings are applied permanently, and the connection between the coating and the substrate is ensured by the mutual diffusion of aluminum and iron, which leads to the formation of intermetallic phases. The study examines Al-Si coatings used in the automotive industry. The research included assessment of coatings in terms of structure, hardness distribution of elements, and surface condition (roughness). The chemical composition of the coatings was determined using EDX microanalysis and phase composition by diffractometric analysis. The final assessment focused on the impact of bending on the quality of the connection between the substrate and the coating.