The minimum allowable thickness of galvanized flat iron 40x4 for grounding is what is the minimum allowable thickness of the ground flat iron I do not remember in the specification?

According to Article 3.2.6 and Table 3.2.6-1 of GB50169-2006 Code for the Construction and Acceptance of Grounding Devices for Electrical Installation Engineering, when flat steel is used as the grounding body, the minimum thickness when laying in the ground room is 3mm, and the minimum thickness when laying in the ground outside is 4mm. The minimum thickness of the underground AC current loop is 4mm, and the minimum thickness of the underground DC current loop is 6mm.