Rare earth-based electrolytic coloring method, electrolyte, and alloy product

A rare earth-based electrolytic coloring method, applied to magnesium alloy, titanium alloy, or aluminum alloy and comprising:

• placing a workpiece into an electrolytic tank for anodic oxidation, wherein a fine and uniform oxide film is formed on a surface of the workpiece after electrification;
• keeping the workpiece in the electrolytic tank continuously for an electrolytic coloring treatment, wherein after the oxide film is broken down, melted, sintered, and reformed, a ceramic film layer forming a metallurgical bond to a substrate is generated;
• and during the electrolytic coloring treatment, a voltage is risen to between 300V to 440V, and then under a high-frequency constant-voltage mode, a thickness of the ceramic film layer is increased, wherein a thickness of a surface oxide film is 15-100 μm and voltage frequency is 50-100 kHz;
• subjecting the electrolytically colored workpiece to water rinse;
• washing, with warm water, the workpiece subjected to water rinse;
• and
• air-drying and baking the workpiece washed with warm water;
• wherein a component ratio of an electrolytic coloring electrolyte during the electrolytic coloring treatment is as follows:
• 5-70 g/L sodium silicate, 3-30 g/L potassium hydroxide, 3-18 g/L potassium fluoride, 5-25 g/L sodium fluoride, 1-18 g/L sodium tungstate, 5-25 g/L ammonium metavanadate, 2-10 g/L disodium ethylenediamine tetraacetic acid, 1-9 g/L triethanolamine, 1-18 g/L potassium ferrocyanide, 3-13 g/L sodium tetraborate, 5-15 g/L glycerol, 2-15 g/L sodium carbonate, 3-10 g/L hexamethylenetetramine, and 1-2 g/L rare earth salts;
• and
• the rare earth salts are a mixture of one or more of cerium nitrate, lanthanum nitrate, and dysprosium nitrate and one or more of yttrium nitrate, neodymium nitrate, and thulium nitrate.