Institute of Light Materials and Technologies Ltd., Moscow, Russia
A. O. Ivanova, Project Leader, e-mail: Anna.Ivanova4@rusal.com
D. K. Ryabov, Chief Scientific Officer
A. Yu. Gradoboev, Department Director
Yu. V. Malakhova, Specialist

Aluminium is widely used in construction for exterior and interior decoration. For this, panels made of anodized alloy sheets, mainly of the Al – Mg system, are used. However, the chemical composition of an alloy grade may vary from batch to batch. This may lead to colour variation in construction elements, as well as to additional costs associated with the need to replace panels that stand out against the general background. This paper describes a study that looked at how the composition of the alloy 5005A influences the appearance of the anodic coatings of sheets in the H24 as-supplied state. It is shown that an increase in iron and silicon content affects the glitter of anodic coatings. Another effect includes a darkened colour of anodized sheets. The probable cause is an increase in the surface roughness after etching and anodizing and the presence of ferrous phases in the nearsurface layers and in the coating, which refract the impinging light. A negative effect of iron and silicon impurities on the specular gloss of uncoated sheets was noted during visual assessment. The decreased reflectivity of the sheets correlates well with the data on the decreased glitter of anodic coatings.

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