Deposition of amorphous phosphate coatings on aluminum

Amorphous phosphating of aluminum and its alloys AÐ"H, Ð"1, and Ð"16 is studied. It is found that uniform coatings are deposited at pH 4.5 at a temperature of 50°C from the solution containing MoO ^sub 4^ ^sup 2-^ promoting ions. By using the x-ray photoelectron spectroscopy, it is shown that phosphates of aluminum and Mo(IV, V) are the predominant components of phosphate coating. By the "thin layer" method, it is found that, in the near-surface layer, alkalization of solution takes place depending on the initial pH value. The dependence pH^sub dep^ = pH^sub in^ ± 0.3 is linear. Phosphate coatings, which are deposited in the solution pretreated with magnetic field (MF), differ in their properties from the coatings obtained by the conventional procedure. MF can increase or decrease the corrosion resistance of phosphate coating depending on the aluminum alloy.[PUBLICATION ABSTRACT]