Dark colored electroceramic coatings for magnesium

An article comprising at least one metallic magnesium or magnesium alloy surface coated with a dark-colored first layer of an inorganic-based coating chemically bonded directly to the at least one metallic magnesium or magnesium alloy surface wherein the inorganic-based coating has a bilayer structure, comprising:

• a. a first sub-layer directly bonded to the metallic magnesium or magnesium alloy surface at a first interface, said first sub-layer comprising Mg, O, C, P and at least one transition metal element;
• b. a second sub-layer integrally connected to the first sub-layer at a second interface, said second sub-layer comprising external surfaces at an outer boundary of the inorganic-based coating, and optionally internal surfaces defined by pores in the second sub-layer lying interior to the outer boundary of the inorganic-based coating and in communication therewith, said second sub-layer comprising the Mg, O, C, P and at least one transition metal element;
• wherein the weight percent of C in the second sub-layer is greater than that of the first sub-layer.

An article having at least one metallic magnesium or magnesium alloy surface and deposited thereon a composite coating, said composite coating comprising:

• a. a matrix formed by a first layer of an inorganic-based coating chemically bound directly to the at least one metallic magnesium or magnesium alloy surface, said matrix having pores and internal surfaces defined by the pores, at least some of said pores being in communication with an external surface of the first layer and forming openings therein;
• and
• b. a second component, different from the inorganic-based coating, applied to at least a portion of the matrix comprising the pores, said second component being in contact with at least some of the internal surfaces and external surfaces.

A plasma electrolytic deposition electrolyte comprising:

• an aqueous alkaline solution or dispersion, which comprises water, a water-soluble or dispersible organic amine present in an amount of about 50 to about 500 g/l, a source of phosphorus selected from water-soluble oxy acids and salts thereof present in an amount of about 10 to about 85 g/l, and at least one water-soluble or dispersible source of at least one transition metal.