# Microstructural and Corrosion Properties of Burnished 6060 Aluminum Alloy  
[PERSON]  
1 Ni.Va. srl Company, Via Cristoforo Colombo 9, Campodarsego, 35011 Padova, Italy; [EMAIL_ADDRESS]  
[PERSON]  
2 Department of Industrial Engineering, University of Padova, Via Marzolo 9, 35131 Padova, Italy; [EMAIL_ADDRESS] (A.G.S.); [EMAIL_ADDRESS] (D.H.); [EMAIL_ADDRESS] (M.D.)  
[PERSON]  
2 Department of Industrial Engineering, University of Padova, Via Marzolo 9, 35131 Padova, Italy;  
2 [EMAIL_ADDRESS] (M.D.)  
[PERSON]  
2 Department of Industrial Engineering, University of Padova, Via Marzolo 9, 35131 Padova, Italy;  
2 [EMAIL_ADDRESS] (M.D.)  
[PERSON]  
2 Correspondence: [EMAIL_ADDRESS] Tel.: +39-049-827-54982-54  
nonconductive. If the oxide is partially soluble in the bath, the coating appears porous. The porosity of the coating allows coloring of the oxides using organic dyes, inorganic pigments or electrolytic deposition of different metals onto the pores of the film. After the first anodizing step, the components are immersed in specific baths. Electrolytic coloring treatment use alternate current in a bath containing metal salts such as nickel, tin, and cobalt. The resulting layer can be blue, black, golden, or green. The major factors linked to the final color are potential application and treatment time [6; 7].  
Multicolor anodizing has gained importance, especially for the production of instruments panels, nameplates, and in the automotive and appliances fields. This technique provides the formation of two or more different colors on the parts of the surface. The process is divided into two possible configurations: single and multiple anodizing. After a previous complete cycle of anodizing, coloring and sealing, multiple anodizing involves covering of selected areas, stripping of the anodic coating from the uncovered areas and repeating the entire procedure to obtain different colors. Single anodizing is used to achieve a dark shade; a resist is applied and the dye discharges or becomes lighter while the anodic film remains intact. The resist is removed and the operation is repeated to reach each desired shade [8; 9].  
Besides anodizing, many solutions have been developed to color aluminum by a single-step chemical coloring process.  
[PERSON] et al. [10] used aqueous solution with cobaltous nitrate, in which the articles are dipped. The piece was heated and the color appeared. The color depends on the degree of heat: at low temperature a grey superficial film is obtained, at higher temperature the coating appears dark black.  
Black coatings are obtained also by immersion of aluminum in a hot solution containing molybdates or antimony chloride [4].  
[PERSON] et al. [4] achieved color ranging from grey to black, yellow, and brown using an alkaline ammoniacal solution containing triethanolamine and metallic carbonates at operating temperature of 353-363 K.  
[PERSON] et al. [11] studied a way to form a black film on aluminum alloys using a chemical process without first requiring anodizing. The aqueous solution tested contained chlorides, sulfates, and bicarbonate of sodium salts and the operative temperature of the bath was 353-363 K [11].  
In order to have an alternative to anodizing and to reduce energy costs in term of temperature and current, the purpose of this work is to create a colored coating on an aluminum surface with aqueous solutions operating at room temperature or warm temperature using an electroless process. The resulting coated samples were characterized using stereo microscope, SEM, and XRD to evaluate their performance. Moreover, potentiodynamic polarization and EIS tests were performed to study the corrosion behavior of the coatings.