镀锌钢板优劣鉴别方法，缺陷原因分析。
原板缺陷
镀锌板的表面缺陷，如折痕、凹坑和波状边缘等，继续影响镀锌板，成为其表面缺陷。因此，在生产前，生产者必须对原板进行检验。
黑点
a、
镀锌板当锌镀层的纯度不够，金属杂质在锌表面形成原电池时，在有利于析氢的情况下容易在锌镀层表面产生黑点。
b、 当锌镀层中铜、铁、砷等杂质含量较高时，这些杂质经钝化处理后会呈黑色。
c、 原板表面未经充分处理，形成残留物，使部分零件无法镀锌，造成镀锌层缺陷而易脱落，产生黑斑。
d、 由于镀锌程中漏镀，后处理容易形成黑点。
e、
镀锌板镀锌溶液中的残渣或少量黑灰（碳或碳化合物）附着在锌层表面或生活在锌层中，并与锌层牢固结合。成品镀锌板上可见黑点。
f、 磨损黑点。运输、堆放过程中操作粗暴造成。
白锈
镀锌板表面受潮湿或雨水影响。在一定温度下，锌被氧化生成白色粉末。白锈表面的抗腐蚀能力大大降低，影响其使用。
镀锌层不均匀
镀锌板表面镀锌层不均匀，厚度不均匀，表面甚至出现细小颗粒。从镀锌锅出来的带钢表面有多余的液态锌。多余的锌液用气刀（喷高压气）吹掉，以控制锌层厚度。气刀的气压、气刀与带钢之间的距离、带钢的速度将直接影响锌层的厚度。如果气刀供气不稳定或气刀压力不足，锌镀层就会积聚，即锌疤。
镀锌溶液中有残留物或浮渣（金属或非金属夹杂物）。有时这些夹杂物混合在镀锌层中。上海模型船模型机械模型工业模型使其表面出现小圆点，甚至使原板未沾锌，容易造成铁露点。
划痕和擦伤
镀锌钢卷通过拉矫机时，矫直机表面有划伤、划伤等异物。
Original board defect
The surface defects of galvanized sheet, such as creases, pits and wavy edges, continue to affect the galvanized sheet and become its surface defects. Therefore, before production, producers must inspect the original board.
Black spot
a. When
the purity of zinc coating is not enough and metal impurities form galvanic cell on the surface of zinc, it is easy to produce black spots on the surface of zinc coating when it is beneficial to hydrogen evolution.
b. When the content of copper,
iron, arsenic and other impurities in the zinc coating is high, these impurities will appear black after passivation treatment.
c. The surface of the original plate is not fully treated, forming residue, so that some parts can not be plated with
zinc, resulting in defects of the zinc coating and easy to fall off, resulting in black spots.
d. It is easy to form black spots in post-treatment due to missed plating during galvanizing.
e. The residue or small black ash (carbon or carbon
compound) in the zinc plating solution adheres to the surface of the zinc layer or lives in the zic layer, and is firmly combined with the zinc layer. Black spots can be seen on the finished galvanized sheet.
f. Abrasion black spots. It is caused by rough operation during transportation and stacking.
White rust
The surface of galvanized steel sheet is affected by moisture or rain. Under a certain temperature, zinc is oxidized to produce
white powder. The anti-corrosion ability of white rust surface is greatly reduced, which affects its use.
Uneven zinc coating
The zinc coating on the surface of galvanized sheet is uneven, uneven in thickness, and even small particles appear
on the surface. There is excess liquid zinc on the surface of the strip steel coming out of the galvanizing pot. The excess liquid zinc is blown off with an air knife (spraying high-pressure gas), so as to control the thickness of the zinc layer. The
gas pressure of the air knife, the distance between the air knife and the strip, and the speed of the strip will directly affect the thickness of the zinc layer. If the gas supply of the air knife is unstable or the pressure of the air knife is insufficient,
the zinc coating will accumulate, that is, the zinc scar.
Slag inclusion
There are residues or scum (metallic or non-metallic inclusions) in the zinc plating solution. Sometimes these inclusions are mixed in the zinc coating. Shanghai model
ship model mechanical model industrial model makes its surface appear small round spots, and even makes the original plate not stained with zinc, which is easy to cause iron dew point.
Scratches and abrasions
When the galvanized coil passes through the tension leveler, there are foreign matters on the surface of the leveler, such as scratch and scratch.
