In fact, in the metal chemical etching services and processing industry, many customers do not know much about passivation. The editor will analyze the passivation process in detail here.
The passivation of the metal surface is a method of converting the active state of the metal surface into a passive state that is not easily oxidized by exposing it to air or using chemical or electrochemical methods, thereby delaying the corrosion or further oxidation of the metal. The former can be called natural passivation, and the latter can be called artificial passivation.
The passivation treatment of metal workpieces before the production of the anti-corrosion layer for etching processing has two purposes:
- To prevent rust on the metal surface;
- To improve the adhesion of the anti-corrosion layer through the passivation film.
In commonly used metal etching, if the aluminum workpiece does not need anodizing before the anti-corrosion treatment, then the surface of the workpiece should be chemically passivated after cleaning, otherwise the aluminum surface is prone to watermarks during drying or transportation, affecting the bonding strength of the anti-corrosion layer and the aluminum etching substrate. For the surface of the aluminum workpiece, if there is a special need, the chemical oxidation method can be used to increase the thickness of the film layer. Experiments have shown that the aluminum surface with an oxide film layer is easier for the anti-corrosion layer to reliably adhere.
If copper and alloy workpieces are not dried quickly after pickling and washing after etching, copper rust is easily generated on the copper surface, which affects the anti-corrosion effect. At this time, passivation can also be used to prevent the generation of copper rust.
After stainless steel parts are corroded, if the salt spray time needs to be increased, purification should also be used to increase the salt spray time.
Generally speaking, metals that are prone to rust in a water vapor environment can be pre-treated by passivation. When passivating, it should be noted that it is a passivation treatment of the metal surface rather than a chemical oxidation treatment.
This process is not required for every metal. It depends on the properties of the metal material and the requirements for the etching product. At the same time, before deciding whether to use passivation, process tests should be carried out to obtain reliable experimental data before deciding whether to use passivation.
