How to control the PH value of galvanizing passivation?

How to control the PH value of galvanizing passivation?

Mon Feb 05 08:14:07 CST 2024

Galvanizing passivation refers to the process of forming a chemical conversion film on the surface of the galvanizing layer, whose main function is to improve the corrosion resistance and decoration of the galvanizing layer. The passivation process generally includes pre-treatment (degreasing, washing, pickling, washing), passivation treatment and post-treatment (washing, drying) steps. The pH control of zinc passivation solution is an important link in the passivation process, because it directly affects the quality and performance of the passivation film. So how do you control pH?

The control of pH value usually depends on the type of passivation solution used. The common types of galvanized passivation fluids mainly include chromate passivation, phosphate passivation, silicate passivation, etc. The pH range required for different types of passivation fluids is also different.

1. Chromate passivation solution: This is the traditional passivation method, and the pH value of chromate passivation solution is usually maintained between 2-3, but it has been gradually replaced due to the environmental and health hazards of hexavalent chromium.

2. Phosphate passivation solution: phosphate passivation is an environmentally friendly passivation method, and its pH value is usually controlled in the range of 3.5-5.5, which is conducive to the formation of uniform and dense passivation film.

3. Organic passivation liquid: such as trivalent chromium passivation liquid, according to the color can be subdivided into color zinc passivation liquid, blue and white passivation liquid, black zinc passivation liquid. In the case of Bigley's trivalent chromium blue white passivation solution, the pH value is usually maintained in the 3-4 range. Trivalent chromium passivation provides good corrosion resistance while also meeting environmental requirements.

The method of controlling the pH value includes adding acidic or alkaline substances to adjust it in time to ensure the stability of the passivation solution. In addition, the production workshop should regularly monitor the pH value of the passivation solution, using a pH test paper or pH meter to determine, if it exceeds the process requirements, it needs to be adjusted.

Please note that the specific formulation and process conditions of the passivation solution will vary from manufacturer to manufacturer, so when using the trivalent chromium blue and white passivation solution, it is necessary to refer to the relevant product instructions provided by Bigely, or you can consult Bigely engineers for accurate operating guidelines and pH control standards.