Is the blue color of brake disc caused by heat treatment during manufacturing?

If the surface of the new brake disc is blue, it indicates phosphating. This kind of brake disc has been treated with liquid medicine and has a certain antirust effect. However, it only has anti-rust effect during storage, and it has little effect in actual use. The blue color on the surface will be worn off when braking. If the surface of the new brake disc is blue, it indicates phosphating. This kind of brake disc has been treated with liquid medicine and has a certain antirust effect. However, it only has anti-rust effect during storage, and it has little effect in actual use. The blue color on the surface will be worn off when braking. If the surface of the new brake disc is blue, it indicates phosphating. This kind of brake disc has been treated with liquid medicine and has a certain antirust effect. However, it only has anti-rust effect during storage, and it has little effect in actual use. The blue color on the surface will be worn off when braking.