It's a CNC mill work for aluminium anodizing parts. After cnc machining is complete the part is anodized blue.
Unlike most other finishes, anodizing preserves the natural luster, texture, and beauty of the metal itself. The anodized coating is hard, durable, will never peel, and, under normal conditions, will never wear through. Anodizing is a process for finishing aluminum alloys that employs electrolytic oxidation of the aluminum surface to produce a protective oxide coating. The anodic coating consists of hydrated aluminum oxide and is considered resistant to corrosion and abrasion. Conventional coatings are 0.1 to 1.0 mil thick and are essentially transparent but they may be colored like sample above.The following is about Aluminium Mechanical CNC Machining Parts Anodizing.