COMPARATIVE STUDY ON THE ENERGY CONDITION OF THE Al_2O_3 OXIDE LAYER ON THE ALUMINUM ALLOY

摘要

The paper presents investigations of the wettability of Al_2O_3 layers produced by the direct-current method and the reference to its geometrical structure and tribological properties. The layers were made on the aluminum alloy EN AW-5251 using direct-current anodizing at varying production parameters (electrolyte temperature, current density, process time). The aluminum plates before the anodizing process were etched in 5 % potassium hydroxide, then whitened in 10 % nitric acid (V). As the electrolyte, an aqueous solution of 18 % sulfuric acid, phthalic acid and oxalic acid was used. Wettability of the surface was determined by the embedded drop method (measurement of the contact angle). Free surface energy was calculated using the van Oss-Chaunhury-Good method. Measurements of the geometric structure of the surface were made by systematic scanning, determining the basic stereometric parameters from the amplitude group before and after the tribological test. Tribological tests were carried out using a tribological tester T-17 for reciprocating motion on a road with a length of 15 km, under conditions of technically dry friction. A constant slip speed of 0.2 m/s was used, a load of 0.5 MPa was used. The tests were carried out at a constant temperature of 298 K and 60 % relative humidity, T7W polymer was used as the tribo partner. Using the scanning microscope (SEM) images of the surface morphology of Al_2O_3 layers were made at the magnification of 5,000x allowing observation of pores.