镀锌钢板的表面白锈和红锈的分析及预防措施
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白锈和红锈是无花镀锌钢板的常见缺陷。不同厚度的镀锌层会对白锈和红锈的产生时间造成危害吗？
证明材料的镀锌层厚度对镀锌钢板表面白锈产生时间没有影响；镀锌层厚度对红锈的形成时间有影响。镀锌层越厚，红锈的潜伏期越长。
那么镀锌钢板表面的白锈和红锈是如何产生的呢？
锌是一种极为活跃的金属材料。锌的表面会随着空气中的水蒸气而发生变化，形成多层多孔且粘稠的Zn（OH）2。然后，Zn（OH）2会进一步与大气中的二氧化碳反应，形成薄的、高密度的、粘性的碱式碳酸锌（2znco3.3zn（OH）2），这也可以防止锌层的进一步腐蚀。
当镀锌钢板紧密堆放在潮湿的空气中时，镀锌钢板之间的表面没有自由流动的空气，镀锌层的局部表面不会产生形成上述腐蚀产物保护膜的化学变化，但会产生电化学腐蚀和白锈。白锈产生的机理实际上是“氧浓腐蚀电池”的原理。
白锈严重程度的关键在于涂层之间凝结水的组成和在环境中的持续时间。如果凝结水中含有海水中的氯化物，水的电导率会增加，从而增加电化学腐蚀速率，加速镀锌层的腐蚀速率。
White rust and red rust are the common defects of no flower galvanized steel sheet. The different thickness of galvanized layer will do harm to the generation time of white rust and red rust?
Let's prove that the thickness of the galvanized layer of the material has no harm to the white rust generation time on the surface of the galvanized steel sheet; The thickness of zinc coating has an effect on the formation time of red rust. The thicker
the zinc coating is, the longer the incubation period of red rust is.
So how does the white rust and red rust on the surface of the galvanized steel sheet produce?
Zinc is an extremely active metal material. The surface of zinc will change
with the water vapor in the air to form multilayer porous and sticky Zn (OH) 2. Then, Zn (OH) 2 will further react with carbon dioxide in the atmosphere to form a thin, high-density, adhesive basic zinc carbonate (2znco3.3zn (OH) 2), which can also prevent
further corrosion of the zinc layer.
When the galvanized steel sheet is closely stacked and placed in the humid air, there is no free flowing air on the surface between the galvanized steel sheets, and the local surface of the galvanized layer will
not produce the chemical change of forming the above-mentioned corrosion product protective film, but will produce electrochemical corrosion and white rust. The mechanism of white rust is actually the principle of "oxygen concentration corrosion battery".
The key to the severity of white rust lies in the composition of condensation water between coatings and the duration in the environment. If the condensed water contains chlorides from seawater, the conductivity of water will be increased, which will
increase the rate of electrochemical corrosion and accelerate the corrosion rate of zinc coating.
