Introduction to the differences between different types of etching

Stainless steel etching:

Unlike copper or aluminum alloys, stainless steel is not easily oxidized in air, so there is no need for passivation treatment after cleaning, which makes the pre-treatment process of stainless steel much simpler than that of copper and aluminum alloys. Meanwhile, stainless steel has relatively high stability in alkaline solutions, so stronger alkaline solutions can be used for surface treatment, and of course, acidic cleaning agents can also be used for cleaning. There are immersion etching and spray etching methods for stainless steel. If there are requirements for the etching depth of the product, spray etching can be chosen; On the contrary, if the etching depth of the product is not high, soaking method can be chosen.

There are two formulas for etching solutions of stainless steel：
① The etching solution mainly used by the vast majority of etching factories is ferric chloride, and additional substances that can increase etching performance are added as needed, such as nitrate, phosphoric acid, hydrochloric acid, sulfur vein, benzotriazole, urotropine, and acid salts;
② A water-based etching solution prepared with nitric acid, hydrochloric acid, and phosphoric acid. After this etching solution is prepared, it needs to be aged with soft steel and then adjusted to the process concentration range through analysis.

Copper etching:
 Copper etching can be used interchangeably with stainless steel solution. Copper is more active than iron and can reduce iron ions, so etching copper does not require solution; Ink removal also uses strong alkali, but copper is more prone to oxidation and requires reduction treatment after discoloration. So copper etching process is more complex than stainless steel process;

 There is a great degree of freedom in the selection of etching solutions for copper and alloys. Commonly used etching systems include the three atmosphere iron etching system, acidic copper chloride etching system, alkaline atmosphere copper etching system, and sulfuric acid hydrogen peroxide etching system. The three atmosphere iron etching system and alkaline copper chloride etching system are more commonly used. In these etching systems, the sulfuric acid hydrogen peroxide etching system solution is easy to regenerate, and the copper in the etching solution is also easy to recover. However, due to the poor stability of nitrogen peroxide, it is limited in practical production. Although the ferric chloride etching system causes high environmental pollution, it is widely used due to its easy preparation, low cost, and convenient management.

Aluminum etching:
 The specific gravity of the solution required for aluminum etching is relatively low, and it reacts violently with the solution, releasing a large amount of isothermal heat. A low specific gravity can slow down the reaction process. The solution for etching aluminum has a low specific gravity and little reducing value, so the basic waste solution can only be discharged. Therefore, etching aluminum consumes a large amount of solution and produces a lot of sewage. Aluminum ink removal requires nitric acid, hydrofluoric acid, etc. Nitric acid has a strong odor and thick smoke, and hydrofluoric acid is highly toxic, so the process is relatively complex.

 The etching systems for aluminum alloys include acidic and alkaline, with ferric chloride and hydrochloric acid being commonly used as acidic etching systems, and phosphate monofluoride systems also being used. Among them, the application of ferric chloride etching system is common. The etching quality of alkaline etching is better than that of ferric chloride, and the etching cost is lower, making it a better etching method. However, the production cost of the anti-corrosion layer of alkaline etching is higher than that of acidic etching, which is currently the bottleneck limiting the widespread application of alkaline etching.