Protective agent applied to cyanide-free silver plating layer and preparation method of protective agent

The invention provides a protective agent applied to a cyanide-free silver plating layer and a preparation method of the protective agent. The protective agent is stable in component and low in toxicity; and the action principle of the protective agent is that the surface of the cyanide-free silver plating layer is covered with linear chain alkyl mercapto alcohol compounds high in chemical adsorption capability and polycations with a plurality of adsorption sites, oxygen and steam in air are isolated, and the silver surface discoloring probability is decreased. Molecular level gaps in a cover layer are filled with linear chain alkyl alcohol or ether high in liquidity. In the subsequent using process, if a protective layer is damaged, the substances also have a repair function. The compounds with an anti-oxidation effect can be adsorbed onto the surface of the silver plating layer, so that the electric potential level of the plating layer is enhanced, and the anti-oxidation capacity is improved. According to the cyanide-free silver plating layer processed through the protective agent, the surface is bright, and the discoloring resistance is greatly improved. The protective agent applied to the cyanide-free silver plating layer and the preparation method of the protective agent meet the application requirements of decorative plating, functional plating and other multiple fields.