Types of Chemical Processing

Types of Chemical Processing


Chemical milling is a process used to selectively remove material from the surface of workpiece parts by immersing them in a chemical solution. The parts that do not require processing are protected by applying a corrosion-resistant coating.

As the workpiece is immersed in the chemical solution, the exposed surface reacts with it, causing the material to dissolve and be removed. The rate of dissolution is typically between 0.02 to 0.03 mm/min.

Once the workpiece reaches the desired depth, it is removed from the solution. This process involves several steps, including surface pretreatment, application of a protective coating, curing, engraving, etching, cleaning, and deprotection.

The protective layer used in chemical milling is typically made of neoprene or butyl rubber. To shape incisions, a knife is used to cut along the contour of the plate and peel off the protective layer.

Chemical milling is an ideal method for machining shallow concavities and grooves on the surface of thin sheets and thin-walled parts, such as integral reinforced panels, honeycomb panels, skins, and wing leading edge panels for aircraft. It can also be used to reduce the thickness of local dimensions of forgings, castings, and extrusions, as well as etching patterns with a depth of less than 13 mm.

One of the advantages of chemical milling is its simple process and equipment, easy operation, and low investment. However, the processing accuracy is not high, typically ranging from ±0.05 to ±0.15 mm. Additionally, dissolution occurs in the side direction under the protective layer, creating an arc shape between the bottom surface and the side surface of the processed material, which makes it challenging to process sharp corners or deep grooves.

Chemical milling is not suitable for processing loose castings and welded surfaces. With the advancement of digital control technology, some applications of chemical milling have been replaced by digitally controlled milling.


Chemical engraving is primarily used for creating signs and plates.

Lithography is mainly used in the manufacturing of transistors, integrated circuits, and large-scale integrated circuits.

Photolithography is mainly used to produce various printing plates.


Pickling is primarily used to remove scale or rust from metal surfaces.

Chemical polishing is primarily used to improve the surface finish of metal parts or articles.

Chemical deburring is primarily used to remove fine burrs from brittle parts or small sheets.

Photochemical processing

Photochemical processing is a technique that combines photocopying and chemical etching to create complex patterns or shapes on the surface of a workpiece. This method includes several techniques, such as photolithography, chemical die cutting (or blanking), and chemical engraving.

To begin the process, a layer of photosensitive adhesive is applied to both surfaces of the workpiece. Photographic negative films with the desired pattern are then placed on the photosensitive adhesive for exposure and development. The photosensitive adhesive becomes a corrosion-resistant substance after being irradiated with light, forming a corresponding pattern on the workpiece’s surface.

The workpiece is then immersed (or sprayed) into a chemical etching solution. The corrosion-resistant coating protects the underlying metal, allowing the desired pattern or shape to be obtained.

Photochemical processing is widely used for various applications. Chemical die cutting, in particular, is used to process complex and finely shaped sheets (typically 0.025 to 0.5 mm in thickness). This technique is especially useful for sheet parts that are difficult to punch mechanically.

Chemical die cutting is used to manufacture TV picture tube baffles (with 5000 holes per square centimeter), leaf springs, precision filters, micro-motor rotors and stators, fluidic components, liquid crystal display panels, clock pinions, printed circuits, strain gauges, and samples.

Surface treatment

Chemical surface treatments include pickling, chemical polishing, and chemical deburring.

During pickling, polishing, or deburring, the workpiece is immersed in a chemical solution, and there is no need to apply a protective layer on its surface as the chemical solution dissolves the unwanted material.

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