RT Journal Article SR Electronic A1 Michna, Stefan A1 Naprstkova, Natasa A1 Klimecka-Tatar, Dorota T1 Research the Causes of Surface Stains after Eloxal Coating for the Profile from the AlMgSi Alloy Using Substructural Analysis JF Manufacturing Technology Journal YR 2015 VO 15 IS 4 SP 620 OP 624 DO 10.21062/ujep/x.2015/a/1213-2489/MT/15/4/620 UL https://journalmt.com/artkey/mft-201504-0025.php AB The aim of the research was to analyze the delivered profile samples, where appeared the darker spots with an irregular circular shape on the surface of light colored profiles after process of natural anodizing without colouration. Profiles are manufactured with alloy EN AW 6060 (AlMgSi) according to EN 573-3, which was carried out by heat treatment hardening. For material were performed measurements of Brinell and Vickers hardness, Vickers microhardness and substructural analysis in occurrence area of the dark spots and outside of these spots (light area of profile). Based on these analyzes it revealed significant difference of mechanical properties in these individual areas and different substructure of the solid solution α there. Based on knowledge of heat treatment technology is this substructure heterogeneity and diversity of mechanical properties (hardness and micro-hardness) of the given alloy caused by uneven localized cooling after solvent annealing in the hardening process. The occurrence of inhomogeneities is then right to express to different color profile to the surface after the anodizing process.