Additive manufacturing is applied in a variety of industrial environments and is a promising technology that is constantly advancing. This work explores the possibility of developing polymeric coatings and composites on aluminium substrates. The deposition of the PETG polymeric material on aluminium EN AW 5182 has been carried out with the FDM (Fused Deposition Modeling) printing technique using PETG filaments. For this purpose, a surface preparation has been carried out and a diluted PETG primer has been applied to improve the anchorage. The experimental work has studied 4 surface pre-treatments, 2 primer thicknesses and 2 printer bed temperatures, on which a 200 μm PETG thin film was deposited with the 3D printer. The surface topography of the substrates after pre-treatment, the thicknesses and characteristics of the primer, the tensile and shear peel force/pressure of specimens bonded by adhesive to the manufactured PETG sheets were analysed.

The printer used was the Creatility Ender 3, and a solution of uncoloured PETG pellets in chloromethane was used for the primer. The applied layer is obtained with a filament of Ø 1.75 mm, with an extrusion temperature of 235 °C and a printing speed of 40 mm/s.

A Taguchi L8 design of experiments has been used. The variables are, pre-treatments (corundum blasting, acid etching, coarse sanding and fine sanding), primer (saturated and 75% saturation), number of primer coats (1 or 2) and bed temperature (90 °C, 110 °C).

It is observed that the acid etch surface pretreatment, with Ra 3.0-4.5 µm, obtains the highest values of tensile peel pressure, 1.4 to 1.6 MPa, with primer thickness and bed temperature being of little relevance. At the other extreme, coarse sanding with Ra 1.0-1.4 µm gives the lowest values of 0.4-0.7 MPa. These are somewhat higher than in other experiences [1] with aluminium/PP. As for the shear test, the values range between 3-6.3 MPa for the acid etching and 2.0-5.0 MPa for the abrasive and the lowest, again for the coarse grinding, 0.7-1.5 MPa. Now with respect to other experiences such as 2024/ABS, lower values have been obtained [2]. The figure shows the fabrication of a 5182/PETG coated aluminium and a polymeric honeycomb structure as a panel, again with 5182/PETG.