Causes of White Rust and Black Spot on Hot Galvanized Sheet

Pubdate:

2023-08-18

The causes of white rust and black spots are: black spots are formed by further oxidation of white rust. The main causes of white rust are: (1) Poor passivation, insufficient or uneven passivation film thickness; (2) The surface is not coated with oil or the residual moisture on the surface of the strip steel;

白锈和黑斑产生的原因有：黑斑是白锈进一步氧化形成的。

白锈产生的原因主要有：

(1)钝化不良，钝化膜厚度不够或不均匀;

(2)表面未涂油或带钢表面残留水分;

(3)卷取时带钢表面含有水分;

(4)钝化未完全烘干;

(5)在运输或储存中受潮或雨水淋湿;

(6)成品存放时间过长;

(7)镀锌板与其他酸碱等腐蚀性介质接触或存放在一起。

成品在库中最长允许存放三个月，以避免存放过久产生氧化。