304 austenitic stainless steel is the most widely used general-purpose stainless steel material in precision manufacturing industries, featuring excellent corrosion resistance, outstanding ductility, stable mechanical properties and good surface flatness. It contains 18% chromium and 8% nickel elements, forming a dense and stable chromium-rich passivation film on the surface, which enables it to resist oxidation and chemical corrosion in conventional environments. These unique physical and chemical properties make 304 stainless steel the preferred material for ultra-thin precision components, optical accessories, electronic functional parts and automotive precision parts. However, the dense passivation layer and uniform internal structure of 304 stainless steel also bring unique difficulties to precision machining. Traditional processing methods including stamping, CNC milling and laser cutting often cause irreversible problems such as structural deformation, edge burrs, internal stress concentration and thermal oxidation scars on 304 stainless steel workpieces, which cannot meet the ultra-high precision requirements of micro and thin components in high-end industries. As a low-stress, non-thermal and flexible subtractive manufacturing technology, chemical etching has become the most suitable processing method for 304 stainless steel precision parts. This paper focuses on the processing characteristics of 304 stainless steel, systematically discusses its chemical etching mechanism, standardized technological process, key parameter optimization, technical advantages and industrial application value, providing targeted technical reference for precision manufacturing and batch production of 304 stainless steel etched parts.

Chemical etching for 304 stainless steel, also defined as photochemical machining (PCM) for 304 stainless steel, is a precision processing technology that relies on controlled chemical redox reactions to remove redundant metal materials. Different from carbon steel and ordinary alloy steel, the core difficulty of 304 stainless steel etching lies in breaking its compact chromium-rich passivation film. The stable passivation layer on the surface of 304 stainless steel can isolate conventional corrosive solutions, resulting in slow etching speed, uneven material removal and fuzzy pattern edges if using ordinary etching formulas. Therefore, the chemical etching system for 304 stainless steel needs to adopt a special mixed solution formula, which can effectively destroy the passivation film while ensuring uniform and stable corrosion of the base metal without damaging the structural integrity of the workpiece. Compared with 316L stainless steel with higher molybdenum content and 201 stainless steel with poor corrosion resistance, 304 stainless steel has balanced etching performance. It not only has sufficient chemical stability to ensure product durability, but also has moderate etching reaction activity, which is convenient for process control and mass stable production, making it the mainstream material for industrial chemical etching.

The whole chemical etching process of 304 stainless steel follows standardized and rigorous technical procedures, mainly including surface pretreatment, photoresist coating, ultraviolet exposure and development, core chemical etching and post-treatment finishing. Each procedure is optimized for the structural characteristics of 304 stainless steel to avoid common processing defects. Surface pretreatment is the primary key step restricting the etching quality of 304 stainless steel. During rolling, transportation and storage, the surface of 304 stainless steel sheet is prone to oil pollution, dust adhesion and passivation film thickening. If the surface is not thoroughly cleaned, the photoresist will fail to bond firmly, resulting in film falling off, pattern offset and local missing etching. The targeted pretreatment process for 304 stainless steel includes alkaline degreasing, water washing, acid activation and surface hydrophilic treatment. Alkaline solution removes surface organic oil stains, while dilute mixed acid is used for activation treatment to thin the dense chromium passivation film on the surface of 304 stainless steel, improve surface hydrophilicity, and lay a foundation for uniform photoresist lamination and subsequent synchronous etching reaction.

After pretreatment and constant-temperature drying, the 304 stainless steel substrate enters the photoresist coating and exposure development stage. According to the thickness and pattern precision requirements of 304 stainless steel parts, two coating modes are adopted: dry film lamination and wet photoresist coating. Dry film is suitable for conventional batch production of 0.1mm–2mm thick 304 stainless steel sheets, with uniform coating thickness and strong bonding force. Wet photoresist is mostly used for ultra-thin 304 stainless steel sheets below 0.1mm and ultra-fine micro-nano pattern processing, which can fit the tiny surface gaps of thin plates more accurately. After coating, the substrate is aligned and exposed with a customized precision mask under ultraviolet light. The exposed area of the photoresist undergoes polymerization curing to form an anti-corrosion protective layer, while the unexposed area remains soluble. After being cleaned by sodium carbonate developing solution, the to-be-etched area of 304 stainless steel is completely exposed, and the precision pattern is accurately transferred to the metal surface. The edge definition of the developed pattern directly determines the dimensional tolerance of the final 304 stainless steel etched parts.

Core chemical etching is the most critical link in the whole processing of 304 stainless steel, determining the dimensional accuracy, surface quality and pattern consistency of workpieces. The mainstream industrial etching solution for 304 stainless steel is a composite system composed of ferric chloride, high-purity hydrochloric acid and special neutral additives. Ferric chloride acts as the main corrosive agent to dissolve the iron-based matrix of 304 stainless steel. Hydrochloric acid is specially added to destroy the chromium-rich passivation film that hinders the etching reaction, solving the problem of difficult corrosion of 304 stainless steel. The special additives can effectively inhibit excessive lateral etching, optimize the etching flatness, and avoid edge warping and pattern distortion of 304 stainless steel parts. In formal production, spraying etching equipment is used for processing. The uniform atomized spraying mode ensures that the etching solution contacts the surface of 304 stainless steel synchronously, avoiding local over-corrosion or incomplete etching. The key controllable parameters include etching temperature, solution concentration, spraying pressure and processing time. The optimal temperature range for 304 stainless steel etching is 48–52 degrees Celsius. A temperature lower than 48℃ will lead to insufficient reaction activity, slow etching speed and low production efficiency; a temperature higher than 52℃ will cause intensified side etching, rough surface and reduced pattern precision. Reasonable matching of solution concentration and etching time can stably control the dimensional tolerance of 304 stainless steel parts within ±0.01mm.

Post-treatment processing is essential to improve the surface finish and service stability of 304 stainless steel etched parts. After the core etching process is completed, the residual cured photoresist on the surface of the workpiece is removed by alkaline stripping solution. Then neutralization cleaning is carried out to completely remove the residual acidic etching solution on the surface, preventing secondary chemical corrosion and passivation damage of 304 stainless steel. For 304 stainless steel precision parts used in optics, electronics and medical fields, electrolytic polishing treatment can be added to remove tiny etching traces and micro-edge burrs, obtaining a smooth and flat metal surface without damaging the precision size. Finally, multiple high-purity water cleaning and constant-temperature hot air drying are performed to ensure no chemical residue on the workpiece surface. For parts working in humid and corrosive environments, secondary passivation treatment can be carried out to further restore and enhance the corrosion resistance of 304 stainless steel, improving the service life of finished parts.

Compared with traditional processing technologies, chemical etching has unique and irreplaceable technical advantages in the processing of 304 stainless steel. Firstly, the whole etching process is a chemical cold processing without mechanical extrusion, impact and high-temperature thermal effect. It will not cause internal structural deformation and residual stress of 304 stainless steel, which perfectly solves the problem that ultra-thin 304 stainless steel sheets are easy to deform and warp after stamping and laser cutting. Secondly, the etching processing has no mechanical cutting contact, and the edge of 304 stainless steel parts is smooth and burr-free without micro-cracks, which fully meets the high-standard surface requirements of optical precision components and electronic functional parts. In addition, the process has extremely high production flexibility. For 304 stainless steel products with complex patterns such as special-shaped holes, dense meshes and ultra-thin gaskets, it only needs to replace the exposure mask without expensive mold opening, which greatly reduces the production cost of small-batch and multi-variety customized parts. Moreover, the batch consistency of chemically etched 304 stainless steel parts is excellent, which can realize stable mass production of high-precision workpieces.

The chemical etching technology of 304 stainless steel has been widely applied in high-end precision manufacturing fields. In the optical industry, it is used to process 304 stainless steel optical diaphragms, precision mask frames and optical filter fixing brackets. The smooth and stress-free etching surface will not interfere with optical transmission and refraction, ensuring the stability of optical system operation. In the electronic manufacturing industry, etched 304 stainless steel precision filter meshes, conductive shims and shielding parts are widely used in precision electronic equipment, relying on the stable chemical properties and high dimensional accuracy of 304 materials. In the automotive industry, 304 stainless steel etched sensor gaskets and fuel system filter components are applied to automotive precision systems, adapting to complex and variable working environments. In addition, this technology also plays an important role in medical equipment, new energy batteries and aerospace precision accessories manufacturing, becoming a core precision processing method for 304 stainless steel components.

Despite its mature application, the chemical etching process of 304 stainless steel still has certain limitations and room for technical optimization. For 304 stainless steel plates with a thickness exceeding 2mm, the required etching time is significantly prolonged, the lateral etching error increases correspondingly, and the dimensional precision decreases, so it is not suitable for processing thick structural parts. In addition, the passivation film state of 304 stainless steel has individual differences in different batches, which may cause slight fluctuations in etching uniformity if the process parameters are fixed. In the future, the processing technology will develop towards intelligent parameter adjustment and green manufacturing. By optimizing environment-friendly etching solution additives and introducing intelligent constant-temperature and constant-pressure control systems, the etching stability and processing efficiency of 304 stainless steel will be further improved, and the environmental protection performance of the process will be enhanced to adapt to higher-end industrial manufacturing requirements.

In summary, chemical etching is the most suitable precision manufacturing technology for 304 stainless steel micro and thin components. Aiming at the unique passivation film characteristics of 304 stainless steel, the optimized pretreatment, photolithography, targeted chemical etching and fine post-treatment processes can realize stress-free, burr-free and high-precision forming of complex 304 stainless steel parts. Compared with traditional mechanical processing, this technology has prominent advantages in ensuring product consistency, avoiding deformation and reducing customized production costs. With the continuous upgrading of precision manufacturing standards in optics, electronics and new energy industries, the market demand for high-precision 304 stainless steel etched components will continue to grow. Continuous process optimization and technical innovation will further expand the application scope of 304 stainless steel chemical etching technology and provide strong support for the development of high-end precision metal manufacturing industry.