Production and Testing of Anodic Oxide Coatings on Aluminum Tapes for Application on Windings in Electrical Devices

The paper presents the influence of the presence of glycerol on the structure and selected properties of anodic oxide coatings produced on aluminum tapes. These tapes are used to produce windings of electromagnets, transformers and direct drive motors of electric vehicles and timing systems of combustion engines. Replacing copper windings with aluminum strips reduces the weight of the coils by almost half. Replacing pressboard insulation with an anodic oxide coating allows the application temperatures of such coils to be increased (from 105 °C to several hundred). The unit breakdown voltage of anodic oxide coatings produced in sulfuric acid electrolyte (32–52 V/µm) used as insulation is similar to that of the insulation used so far (30–100 V/µm). The addition of 15% glycerol to an electrolyte containing 15% H₂SO₄ allows the production of coatings of the same thickness with half the energy consumption. Due to its higher viscosity than water, glycerol settles on the walls of the produced oxide cells, reducing their secondary dissolution by the electrolyte.