Root-cause Tree for Whitening & Hazing of Seal Coatings
封护层发白与起雾的根因树
标签：发白, 起雾, 根因分析, 湿度, 缺陷诊断
封护发白按"水汽→溶剂→膜层→基面"四层排查。喷涂即时发白：相对湿度超 75% 时快干溶剂蒸发使表面温度低于露点、水汽凝入膜内，对策是将工件加热至高于露点 3 °C 或改用慢干稀释剂；干燥后云雾状：单道膜厚超 40 μm 或层间隔不足，底层溶剂被封在膜内——控制每道 25–30 μm、间隔 2–4 h；一周后局部白斑：基面残盐或手汗吸湿，终洗用去离子水至电导率低于 50 μS/cm 可根除；整面哑光不匀：喷涂重叠率不足 50% 或方向单一，改为十字交叉、重叠 50–60%。每例留存 45° 侧光照片定位成因。
Debug whitening in four layers: moisture → solvent → film → substrate. Instant bloom on spraying: at RH over 75% fast evaporation chills the surface below dew point and traps condensate — heat the work 3 °C above dew point or switch to retarder thinner. Cloudiness after drying: coats over 40 μm or short intervals sealing solvent under — hold 25–30 μm per coat, 2–4 h apart. White patches after a week: residual salts or sweat absorbing moisture — final-rinse with deionized water below 50 μS/cm. Overall uneven matte: overlap under 50% or single-direction passes — cross-hatch at 50–60% overlap. Archive 45° raking-light photos per case to pin the cause.