There are three variable factors in the whole etching process, namely, etching depth, etching speed, and etching time. The relationship between the three is as follows: V=h/t, where V is the metal etching speed (mm/min), the chemical etching speed here refers to the single-sided etching speed, h is the etching depth (mm); t is the etching time (min).

For overall corrosion or forming chemical etching processing and hollow graphic chemical etching, chemical etching is often carried out on both sides at the same etching time. This double-sided chemical etching speed is 1 times faster than chemical etching on only one surface. Under the condition of certain metal materials, there are many factors that affect the etching speed, among which the most important ones are the type, concentration and corrosion temperature of the corrosive agent. If the corrosive agent concentration and etching conditions are certain, the characteristics and heat treatment state of the material also have a great influence on the etching speed.

In order to determine the optimal chemical etching time, the chemical etching speed of the material to be etched should be predetermined before chemical etching, especially after adding additives to the corrosive solution. Usually, a small sample of the same material as the etched material (including material model, heat treatment status and thickness) is used to measure the photot etching speed. After the sample is thoroughly cleaned and its thickness is accurately measured, it is corroded in the corrosive solution. The etching time is generally 10 minutes. The longer the time, the more accurate the etching speed.

Whether the required amount of corrosion processing can be completed within the calculated etching time, two parameters must be controlled in the entire etching process to ensure it. 1. Control of the concentration of the corrosive liquid components: This can be achieved by chemical analysis of the corrosive liquid and replenishing the consumed corrosive agent based on the analysis results. In order to prevent the rapid change of the corrosive agent components, when preparing the corrosive liquid, the volume of the corrosive liquid should be larger if conditions permit (processing volume, cost tolerance of the corrosive liquid, size of the corrosion site, etc.), so that it does not need to stop for analysis and replenishment during the corrosion processing of parts with not too much corrosion. 2. Control of the temperature of the corrosive liquid: The temperature has a certain influence on the etching speed. Within the range of the extreme etching speed, when the temperature rises by about 12°C, the etching speed increases by about 1 times. For parts with precise size requirements, the temperature is required not to exceed ±2°C~±3°C.