Abstract: A method of producing protective coatings that are resistant to corrosion and wear on magnesium and magnesium alloys by anodic oxidation. In order to obtain coatings that have little or no inherent color, that can be easily colored, and that provide a satisfactory adhesive base for lacquering or subsequent processing, a low-alkali aqueous electrolyte bath containing(a) borate or sulfonate anions and(b) phosphate and fluoride or chloride ionsand adjusted to a pH of 5 to 11 and preferably 8 to 9 is employed. A direct current is applied and is either briefly turned off or its polarity incompletely reversed to allow the formation of manganese phosphate and magnesium fluoride or magnesium chloride and optionally magnesium aluminate.

Abstract: A method of preparing the surfaces of magnesium and magnesium alloys by anodic oxidation. To produce protective coatings that have little or no inherent color, that can easily be colored, that provide a satisfactory adhesive base for lacquering or subsequent processing, and that exhibit outstanding resistance to corrosion and wear on magnesium and magnesium alloys by anodic oxidation, an alkali-rich aqueous electrolyte bath containing(a) borate or sulfonate anions and(b) phosphate and fluoride or chloride ionsand adjusted to a pH of 8 to 12 and preferably 10.5 to 11.5 is employed. A direct current is applied and is either briefly turned off or its polarity incompletely reversed to allow the formation of magnesium phosphate and magnesium fluoride or magnesium chloride and optionally magnesium aluminate.