The principle of the brightening process in the galvanizing process is to improve the surface quality of the substrate and promote adhesion of the zinc coating. The process involves several steps, including cleaning, pickling, rinsing, activation, and brightening.

During the first step, the substrate is cleaned to remove dirt, grease, and other contaminants. Next, the substrate is pickled in an acid solution to remove any oxide or other surface scale. The pickling acid commonly used is hydrochloric acid.

After pickling, the substrate is rinsed to remove any residual acid or other contaminants. The next step is activation, which involves treating the surface with an acidic solution, such as sulfuric acid. This helps to create a reactive surface that is more receptive to the zinc coating.

Finally, the substrate is treated with a brightening solution, which typically contains a mixture of various chemical compounds such as stabilizers, brighteners, and surfactants. The brightening solution helps to remove any remaining impurities, promote adhesion of the zinc coating, and create a smooth and shiny surface.

Overall, the brightening process plays a crucial role in the galvanizing process by enhancing the surface quality of the substrate and improving the functionality and aesthetic appeal of the final product.