Optimization of anodizing process parameters to improve adhesion between fiber reinforced polymers and 3D-printed metal substrates with macroscopic pins
Topic(s) : Material and Structural Behavior - Simulation & Testing
Co-authors :
Riccardo RICCARDO MIRANDA (ITALY), Vincenzo FIORE (ITALY), Francesca MAZZARA , Francesco DI FRANCO (ITALY), Alberta AVERSA , Sara BIAMINO (FRANCE), Eleonora ATZENI (ITALY), Fabrizio SARASINIAbstract :
The efficient production of components endowed with high functionality is crucial for today’s industries. This objective can be reached by combining multiple materials that differ in properties as well as by possibly tailoring their placement in the component through a simple and unique manufacturing process. One of the material combinations employed involves metals and fiber reinforced polymers, as both materials are commonly used in engineering industries. This combination can be exploited to manufacture products that enable a required technical functionality at lower weight and costs than generally achievable by other means.
In such a context, surface treatments are required to improve the adhesion between different substrates and a wide literature can be found about several types of treatment aimed at increasing the mechanical performances of polymer-metal composite joints [1]. Mechanical treatment with sandblasting or sandpaper is the simplest one but it is not so effective to increase the mechanical properties and, at the same time, to protect the joined component from the surrounding aggressive environments during its service life. In the latter case, chemical treatment by using coupling agents or anodizing can be considered more suitable approaches [2]. In particular, the anodizing process produces a porous oxide layer on the metal surface, whose properties depend on the temperature, voltage and composition of the electrolyte. Furthermore, the anodic layer protects the metal substrate against corrosion. The most common bath for the anodizing process used chromic acid (CAA) but it is currently illegal due to the high risk of Cr(VI) pollution. It was widely used to produce a porous layer that provides high mechanical interlocking and corrosion protection, but today the challenge is to replace it with eco-friendly baths. A possible replacement for CAA is tartaric-sulphuric acid anodizing (TSA) [3], which creates a layer with high corrosion resistance, but it doesn’t allow to obtain joints with acceptable mechanical performances. When the main goal is achieving good adhesive bonding, phosphoric-sulphuric acid (PSA) seems to be more appropriate [4].
In this work, the feasibility of the anodizing process on 3D-printed metal will be evaluated. In particular, AlSi10Mg alloy substrates with macroscopic 3D-printed pins will be used with the aim of improving the adhesion with fiber reinforced polymer substrates, manufactured through vacuum infusion technique. Different electrochemical treatments will be investigated and the growth of the porous layer on the pin surface will be analyzed to highlight critical issues, such as the difficulty of developing an oxide layer over a 3D surface with complex shape. In addition, several baths will be investigated in order to optimize the anodizing process parameters thus achieving a good compromise between the mechanical performances of the joints and their good corrosion resistance by using a single bath.
In such a context, surface treatments are required to improve the adhesion between different substrates and a wide literature can be found about several types of treatment aimed at increasing the mechanical performances of polymer-metal composite joints [1]. Mechanical treatment with sandblasting or sandpaper is the simplest one but it is not so effective to increase the mechanical properties and, at the same time, to protect the joined component from the surrounding aggressive environments during its service life. In the latter case, chemical treatment by using coupling agents or anodizing can be considered more suitable approaches [2]. In particular, the anodizing process produces a porous oxide layer on the metal surface, whose properties depend on the temperature, voltage and composition of the electrolyte. Furthermore, the anodic layer protects the metal substrate against corrosion. The most common bath for the anodizing process used chromic acid (CAA) but it is currently illegal due to the high risk of Cr(VI) pollution. It was widely used to produce a porous layer that provides high mechanical interlocking and corrosion protection, but today the challenge is to replace it with eco-friendly baths. A possible replacement for CAA is tartaric-sulphuric acid anodizing (TSA) [3], which creates a layer with high corrosion resistance, but it doesn’t allow to obtain joints with acceptable mechanical performances. When the main goal is achieving good adhesive bonding, phosphoric-sulphuric acid (PSA) seems to be more appropriate [4].
In this work, the feasibility of the anodizing process on 3D-printed metal will be evaluated. In particular, AlSi10Mg alloy substrates with macroscopic 3D-printed pins will be used with the aim of improving the adhesion with fiber reinforced polymer substrates, manufactured through vacuum infusion technique. Different electrochemical treatments will be investigated and the growth of the porous layer on the pin surface will be analyzed to highlight critical issues, such as the difficulty of developing an oxide layer over a 3D surface with complex shape. In addition, several baths will be investigated in order to optimize the anodizing process parameters thus achieving a good compromise between the mechanical performances of the joints and their good corrosion resistance by using a single bath.