Requirements for zinc coating treatment of hot dip galvanized products in power fittings

1 hot dip galvanizing solution

The total impurity content (except iron, tin, aluminum, nickel) in zinc solution used for hot dip galvanizing of electric power fittings shall not exceed 1.50% of the total mass. Refer to gb/t470 for the impurities.

2. Surface treatment requirements before galvanizing

2.1 the surface of workpiece shall be flat, smooth, without burr on the edge and free from defects such as spots, pits, scratches and other defects affecting the quality before galvanizing. 5.2.2 before plating, the surface oil, rust, welding slag and oxide layer shall be removed. The pretreatment shall comply with the relevant provisions in Appendix C of gb/t13912-2002.

Appearance of 3 zinc layer

3.1 the zinc layer shall be continuous and smooth, and it is not allowed to have the zinc layer exudated from the acid returning macular. The presence of dark or light gray uneven color areas with zinc layer thickness meeting the requirements shall not be the reason for rejection of products.

3.2 zinc leakage spots with diameter less than 0.5mm are allowed on local surfaces.

3.3 for the parts with connection, contact and corona protection requirements, no convex tumor is allowed.

3.4 concentrated zinc free zone, convex tumor and ripple are not allowed on the surface of plating parts. The total area of scattered zinc free zone, bump and ripple shall be as follows:

a) The general parts shall not exceed 0.5% of the total area of the plating parts;

b) Large parts (such as pressure equalizing shield ring, large plate or surface area more than 2000cm ² The part of) shall not exceed 0.1% of the total area of the plating part; c) The zinc leakage spots on the galvanized surface of the weld are allowed, and the total area shall not exceed 3% of the weld area.

The above zinc free area shall be repaired by zinc rich paint or by welding with low melting point zinc alloy electrode. The use of zinc rich paint shall comply with hg/t3668.

3.5 the surface defects of workpiece before galvanizing, such as sand hole and slag inclusion caused by casting and forging process, shall not be regarded as the quality defect of coating.

4 thickness of zinc layer

After sampling, the zinc thickness of the sample and the overall zinc thickness of the sample shall not be lower than the small value specified in Table 2.