Electroplated coating pinholes and stripes on electric heating tubes

Electroplated coating pinholes and stripes on electric heating tubes

The appearance of pinholes and stripes in the coating, sometimes occurring simultaneously or separately, is mainly caused by additives.

There are two situations caused by additives: firstly, the coating is particularly bright; Secondly, the brightness of the coating is very poor. The former is due to excessive brightener, while the latter is due to insufficient carrier brightener. When there is too much brightener in the solution and dilution with water is ineffective, the galvanizing process often uses hydrogen peroxide to remove it. This not only oxidizes and decomposes the brightener, but also removes iron impurities in the solution through oxidation and filtration. However, the zinc iron alloy process should not be treated with strong oxidants such as hydrogen peroxide or potassium permanganate, and can only be treated with large doses (5-7gL) of powdered activated carbon, which not only delays production but also increases costs. Therefore, the brightener needs to be added frequently and rarely to avoid this malfunction. The latter carrier has too little brightener, and a small amount should be gradually added until the fault is removed. Do not add too much. In this process, the carrier brightener is integrated into the cylinder opening agent, and can be eliminated by adding it.

Due to the small size of the needle hole, it is difficult to see, and even slight negligence can make it difficult to detect. Striped air flow appears when the current is high, the opening agent is too low, and the amount of hydrogen evolution is high. There are many areas with high current density, and sometimes there are also other areas. By appropriately reducing the current density, it can be eliminated.

Pinholes and stripes also appear when the pH value is too high. The chloride zinc iron alloy plating solution exhibits weak acidity. Due to the easy oxidation of Fe2+to Fe3+, during the oxidation process, the pH value increases and the acidity of the solution decreases. When the pH value rises above 5, hydroxide is generated, forming pinholes or stripes.

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