Hot-dip Galvanizing Defect Detection and Rework Process For Cable Trays, Based On GB/T13912 Standard

In factory power distribution projects, unqualified galvanized coating is the main reason for cable tray acceptance rejection. Direct batch return will cause project delay and extra logistics cost. Based on Chilok electrical MRO acceptance experience, defects are divided into manufacturing defects and storage secondary rust defects, and targeted repair schemes are proposed to pass engineering inspection without goods return.

1. Cause Analysis Of Four Common Galvanizing Defects

1. Edge missing plating: Excessive surface tension of cutting sharp corners leads to poor zinc adhesion, belonging to manufacturing defect;

2. Welding peeling: Unclean welding slag forms oxide interlayer and reduces coating adhesion;

3. Zinc tumor defect: Incomplete acid pickling causes impurity accumulation, scratching cable insulation during installation;

4. Storage white rust: Stacking damp leads to secondary oxidation of zinc layer.

2. Mandatory National Standard Acceptance Indicators

According to GB/T13912-2022, outdoor cable tray requirements: average coating thickness ≥65μm, minimum local thickness ≥55μm; no peeling after 180° bending test; no red rust after 96h neutral salt spray test. Indoor dry environment thickness can be relaxed to 45μm.

3. On-site Non-destructive Rework Procedure

1. Edge missing plating: Spray two layers of 95% zinc-content cold galvanizing paint with 15min interval, supplement thickness above 60μm;

2. Welding peeling: Polish oxide interlayer with nylon abrasive disc to avoid base metal damage, passivate and repair coating;

3. Zinc tumor removal: Polish with 800-mesh abrasive tools, coat sealing passivator to prevent pitting corrosion;

4. White rust elimination: Wipe with diluted oxalic acid, neutralize and dry, spray transparent sealing coating for re-inspection.