①Inspection of China Nut; visually inspect the surface quality of the bolts. Any burrs left by machining must be removed and sharp edges must be rounded.② Manual degreasing; ensure that there is no grease on the surface of the substrate.③Soak and remove oil; put the bolts in alkaline water and boil to remove the surface oil.④Pickling: In order to prevent the alkaline degreasing solution from...