What causes oil slicks in the potassium chloride galvanizing process? (Part II)

What causes oil slicks in the potassium chloride galvanizing process? (Part II)

Tue Dec 12 09:56:13 CST 2023

The emergence of oil slicks in the potassium chloride galvanizing process is not only related to the decomposition of the brightener, but also to the high concentration of potassium salt.

Excessive concentration of potassium salts

Zinc chloride plays two roles in potassium chloride galvanizing solution, it is both the main salt that provides ions and the conductive salt. However, if there is only zinc chloride in the plating solution, then the conductivity of the solution is poor, so potassium chloride must be added, so it is also called potassium salt plating solution.

potassium chloride galvanizing brightener BZ-528

Due to the above two functions, potassium chloride forms a stable complex ion with zinc ion, thereby increasing the cathode polarization. However, the concentration of potassium chloride is too high, especially when it exceeds the upper limit of the allowable dissolution concentration of the brightener, the brightener will decompose and precipitate, resulting in an oil slick (or turbidity) of the bath. At this time, if we also add potassium chloride galvanizing brightener to the plating solution, then it will also cause the plating solution to "precipitate salt" and float flocs.

Control potassium chloride concentration

How to control the content of potassium chloride? Galvanizing plants need to make appropriate adjustments according to seasonal temperature differences. Take Bigely's potassium chloride galvanizing brightener BZ-528 as an example, the potassium chloride is usually controlled at about 180g/L in summer and 200g/L in winter.

Generally speaking, potassium chloride is not consumed in the bath, and only brings out the loss. Therefore, the electroplating factory in the use of potassium chloride galvanizing brightener, it is recommended not to add more potassium chloride, if its content is too high, easy to cause the bath turbidity.

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