Appearance Inspection Requirements for Powder Coated Workpieces

1. General Inspection Rules

⑴These requirements apply to surface appearance quality inspection of all electrostatic powder coated workpieces. Judgment is based on visual observation, hand feel and simple tool measurement.

⑵Inspection environment: Natural light or 40W standard white light. Observe from multiple angles with a viewing distance of 300~500mm from the workpiece surface.

⑶Inspection tools: Color difference card, coating thickness gauge, cross-cut tester, adhesive tape, straight ruler, 等.

⑷Inspection can only be conducted after workpieces cool down to room temperature with no dust, water stains or oil contaminants on the surface.

2. Basic Overall Appearance Requirements

⑴The coating shall be intact and uniform, fully covering all coated areas without substrate exposure, missing coating or insufficient powder coverage.

⑵The surface shall be flat and smooth, free of bulges, particles and rough burrs.

⑶The surface shall be clean without obvious stains, fingerprints, water marks and oil deposits.

⑷Powder coating shall be fully applied on corners, bends, weld seams, grooves and dead corners with no partial thin coating.

3. Color and Gloss Requirements

⑴Colors shall conform to standard samples and drawing color codes with no obvious color difference. Workpieces in the same batch shall have consistent hue without uneven shade and two-tone effect.

⑵Gloss shall meet order specifications including high gloss, matte and semi-matte. Uniform gloss is required on single workpiece with no partial bright or dark areas.

⑶Foreign color spots and patches are prohibited.

4. Appearance Defect Judgment Criteria

4.1 Unacceptable Defects (Directly Rejected)

⑴Substrate exposure, missing coating, large-area powder peeling and coating detachment;

⑵Obvious bubbles, pinholes, shrinkage cavities, cracks and sagging powder accumulation;

⑶Severe scratches, dents and sharp abrasions damaging the coating surface;

⑷Large-area pockmarks, orange peel texture and agglomerated particles;

⑸Rust and black oxide layers on coated surfaces;

⑹Accumulated caked powder and severe powder sagging.

4.2 Allowable Minor Defects (Judged by Product Grade)

⑴Tiny dust particles: Acceptable if small in quantity and size without affecting overall appearance;

⑵Shallow faint scratches: Permitted on non-critical surfaces if coating and base material remain intact;

⑶Slight corner wear: Allowed on inner fitting and hidden positions with no visual impact.

5. Requirements for Corners, Holes and Fitting Surfaces

⑴Coating thickness on sharp corners and edges shall be moderate, free of heavy powder burrs and edge chipping.

⑵Screw holes, mounting holes and through holes shall not be blocked by excess powder with neat openings to ensure normal assembly.

⑶Fitting surfaces and welds shall be fully coated without thick powder buildup causing assembly misalignment.

⑷No coating cracking or peeling on bent sections.

6. Sampling Inspection for Coating Performance

⑴Coating thickness: Controlled per product standard, normally ranging from 60~120μm. Even thickness distribution is required with no local ultra-thin or ultra-thick areas.

⑵Adhesion test: No massive coating peeling after cross-cut test; no powder flaking after tape pulling test.

⑶Friction resistance: No color fading or powder shedding under normal wiping.

7. Batch Judgment & Disposal

⑴Single workpiece with prohibited defects on key visible surfaces shall be deemed unqualified and sent for rework or scrapped.

⑵Full re-inspection and recoating shall be carried out for batches with prominent color difference and inconsistent coating quality.

⑶Workpieces with minor flaws that do not affect usage, appearance and anti-corrosion performance can be accepted as qualified products.