There are many kinds of metal protective layers. For a special-shaped spring, a metal protective layer is generally obtained by electroplating. Plating protective layer can not only protect against corrosion, at the same time can improve the appearance of the shaped spring. Some electroplated metals can also improve the working properties of special-shaped springs, such as increasing the surface hardness, increasing the wear resistance, increasing the thermal stability, and preventing radiation corrosion.
If purely for the irregular spring corrosion, the electroplated zinc layer and the electroplated cadmium layer should generally be selected. Nickel-plated special-shaped spring zinc is relatively stable in dry air, hardly changing and difficult to change color. A white film of zinc oxide or carbon zinc carbonate is formed in humid air. This dense film prevents further corrosion. Therefore, the galvanized layer is used for the anti-corrosion protection layer of the profiled spring under normal atmospheric conditions. All kinds of special springs that work in contact with solutions of sulfuric acid, hydrochloric acid, caustic soda, and humid air in an atmosphere such as sulfur trioxide are not suitable for zinc plating.