Phosphating drywall screw is the most basic product line, and blue and white zinc drywall screw is a supplement, the scope of application and purchase price of the two are basically the same. The slight difference is that the black phosphating has a certain lubricity, the attack speed (into the specified thickness of steel plate speed, is a kind of quality assessment index) is slightly better; And the blue and white zinc in the anti-rust effect is a little better, and the color of the product is light, not easy to paint after the color. There is almost no difference in anti-rust ability between blue and white zinc and yellow zinc, which only lies in the difference of use habit or user preference