Galvanized layer thickness is a hard metric of cage rust protection; too thin and it rusts within two or three years—acceptance cannot be signed just because it looks silver-bright. Zinc thickness must be measured instrumentally; the eye can only judge missing or runny plating.
Common industry standards: hot-dip galvanized cages have average zinc layer no less than 85μm, local no less than 70μm; electroplated cages are generally 8~15μm. The purchase contract should specify zinc thickness and test method; otherwise acceptance has no basis, and the manufacturer's word is law.
On-site testing uses a magnetic thickness gauge (eddy-current/magnetic dual-mode), taking 3 measurement points at each cage's four-corner posts, base frame, and mesh surface, and averaging. Points must be cleaned of surface oil for accurate readings; thin coatings must avoid weld seams and corners, where thicker plating does not represent overall level.
Beyond thickness, inspect appearance: whether the surface has missing plating, exposed steel, zinc spatter, or scratches; whether weld seams are blackened and unplated. Focus on cage corners, mating faces, and inner walls—these plating blind spots often have thin or no coating. Mark exposed-steel spots on site and require re-galvanizing before sign-off.
Acceptance advice: sample-test no less than 10% of the first batch; if the whole-batch rejection rate exceeds 5%, require rework and re-galvanizing. Nanjing Tongnuo Warehouse Equipment Manufacturing Co., Ltd. ships with a zinc-layer test report; customers may re-measure on site, with data traveling with the goods.