The thickness of the galvanised layer can be measured by specific test methods. According to the national standard GB/T13912-2002, for parts with a main surface area of more than 2 square metres, the average thickness of galvanised layer measured on all basic measuring surfaces of each part in the sample shall be not less than the minimum value of its corresponding average thickness of galvanised layer. For parts with a major surface area of less than or equal to 2 square metres, the local thickness of the coating measured on each basic measurement surface shall be not less than the minimum of its local thickness, and the average thickness of the coating measured on all basic measurement surfaces of the sample shall be not less than the minimum of its corresponding average thickness.

Importance of zinc coating thickness

The thickness of the zinc coating directly affects the corrosion resistance of the plated parts. The user can choose a zinc coating thickness higher or lower than the standard as required. The thickness of the zinc coating may be higher than that specified in this standard for parts that are subjected to very severe corrosive conditions and/or require a longer service time. However, the thickness of the galvanised layer is also subject to the chemical composition of the substrate, the surface condition of the parts, the geometry of the parts, hot dip plating process parameters and other factors.

In summary, the national standards for the thickness of the galvanised layer of galvanised steel are based on the thickness of the workpiece, the exact values of which can be found in the relevant national standards documents. These standards ensure that galvanised steel sheets provide adequate protection against corrosion in the intended environment.