Galvanized steel has excellent corrosion resistance and bright appearance, and is widely used in construction, home appliances, automobiles and other industries. Leakage plating is a common surface defect of hot-dip galvanizing, which seriously affects the corrosion resistance and appearance of galvanized sheets, and even affects the formability of galvanized sheets.

When the surface of the galvanized steel sheet is not completely exposed to the base metal or the dipping flux is insufficient, leakage plating will occur during dipping. The reasons for this quality defect are as follows:

  1. Leakage plating caused by raw materials and influencing factors in the manufacturing process. The influencing factors are:

Excessive oil or rust (often localized corrosion); paint marks; weld skin at the weld; defects in the steel; scars, slag inclusions;

  1. The pretreatment process is not perfect and the leakage plating caused by improper operation.

The workpiece clamping is unreasonable, there is overlap, the phenomenon of air pockets and the lack of activity in pickling;

Under-pickling caused by acid aging and short pickling time;

Poor degreasing, there are individual dirt;

The composition of the fluxing solution is reduced, resulting in insufficient fluxing effect.

  1. If it stays in the air for too long before drying, new corrosion products are formed on the surface of the workpiece.
  2. The drying temperature is too high, causing the local flux layer to burn.
  3. There is a problem with the composition of the zinc solution. For example, if the aluminum content is too high (>0.05%), it is easy to cause leakage plating.
  4. The immersion speed is too slow or pauses in the middle, and the flux layer is burned or the complex workpiece has pockets. During the immersion plating, individual parts of the workpiece cannot be contacted with the zinc solution and leak plating.

In short, according to the reasons for the defects of galvanized steel sheet, targeted measures are taken, and the problem of leakage plating can be solved. In addition to taking corresponding countermeasures for the above reasons, the most important thing is to set up an inspection process for pretreatment. That is, after taking it out of the flux tank, carefully inspect the surface of the galvanized steel sheet, find out the individual parts that are not up to the standard in the pretreatment in time, and take measures to eliminate them.