“Good appearance, no scratches” is not objectively inspectable. Grade surfaces and define viewing distance, angle, lighting, time, allowed defect size/count/zone, plus approved limit samples for boundaries that words cannot capture. Separate cosmetic acceptance from dimensional and corrosion performance.
Values in this article support engineering screening during design review, RFQ and prototyping. They do not replace formal calculations, material data sheets, qualified procedures or contractual standards.
WORKABLE GRADING
- Class A: continuously visible in normal use, e.g. front panel; example condition 500–700 mm, about 1,000 lx diffuse white light for 5–10 s. - Class B: occasionally visible after installation; larger defect or longer distance may be allowed. - Class C: hidden but must still assemble and resist corrosion; focus on burrs, sharp edges and coating continuity. These are example company conditions, requiring customer/sample approval. Do not magnify defects using phone flash or extreme grazing light outside the defined setup.
COLOR, GLOSS AND TEXTURE
Color may use CIEDE2000 ΔE00; demanding cosmetic work often begins discussion near 1.0–2.0, but gloss, texture and metallic effect alter perception. Fix instrument geometry, illuminant/observer, measurement points, substrate and master-lot. Gloss may follow ISO 2813:2014; profile texture parameters use ISO 21920-2:2021, replacing withdrawn ISO 4287. Equal Ra does not imply equal lay or peak/valley form.
PROJECT CHECKLIST
Surface map; viewing condition; defect atlas; color/gloss; grain direction; weld blending; edges; limit-sample validity/storage.