How to deal with irregular pits formed on the surface of sheet metal parts?

Common defects in surface treatment of sheet metal parts do not need spraying. Standard defect definition of sheet metal parts appearance inspection rainbow effect: zinc plating may cause discoloration or "rainbow" effect. Rust/oxidation: Chemical reaction on metal surface exposed to air. Color change: the background color or expected color changes, or the color and luster of different areas on the surface of the part are inconsistent. Scratch: a strip-shaped shallow groove on the surface of a part. Indentation: groove marks on the surface of parts caused by sharp objects, which can be felt with nails. Electroplating mark/flow mark: abnormal ripple or stripe area formed on the surface of parts due to uneven coating thickness. Trace: refers to the pits, bending traces or other traces of the matrix material, which cannot be eliminated after painting. Dust or grease: dirty (unwashed) left on the surface of parts during manufacturing. Spots/sand/wool: Any unexpected foreign matter on the surface of coating or parts. Protrusion/Pit: A defect similar to a crater on the surface of a part. Die Indentation: Due to the process trace caused by the molding die on the surface of parts, the position and size of die indentation of all parts are the same, and they are evenly distributed in the molding/bending area. Indentation marks: can the indentation of convex and concave dies be combined into one? Standard defect definition of appearance impurities in liquid/dry powder spraying: there are foreign substances in the spraying layer. Dent: The local dent on the sprayed surface caused by the substrate indentation (including tool marks, die indentation and bending indentation). Stripping: the sprayed surface falls off locally. Scratch: There are scratches on the spraying surface, which have hurt the bottom layer and exposed the color of the metal substrate. Orange peel: the sprayed surface is wrinkled due to poor adhesion of paint, and locally bulges are accumulated, which looks like orange peel or wrinkles (except wrinkle removing powder). Flow mark: there are liquid bumps on the spraying surface, and the top is bead-shaped. Discoloration: the color (depth) of the sprayed surface is inconsistent. Pinhole: tiny holes similar to those formed by needling can be seen on the surface of the coating (the metal substrate cannot be exposed, and the exposure is regarded as peeling). Bubble: poor local adhesion of spraying leads to film bulging. Stain: Due to the defect or uncleanness of the base material, the painted surface of the parts has stains or irregular colors. Hanging marks: the marks left on the spraying surface due to the shielding of the installation auxiliary tools (the metal substrate can not be exposed, and it is regarded as peeling when exposed). Wear: there are scratches on the sprayed surface, but the metal substrate is not damaged. Cracking: There are tiny cracks on the sprayed surface. Pitting (shrinkage cavity/fisheye): A number of small circular pits with different sizes and different distributions remain after the coating is dried (the metal substrate cannot be exposed, and the exposure is regarded as peeling). Thick edge: the phenomenon of coating accumulation at the edge or internal corner of the product during spraying. Color difference: The drawn color is inconsistent with the color of the standard color sample and uneven.