Stainless steel etching process, also known as stainlesssteel photochemical etching or photochemical machining (PCM), is a subtractive metal manufacturing method that produces precise patterns, microholes, slots and complex profiles on stainlesssteel sheets. Instead of mechanical stamping, shearing, laser cutting or CNC milling, this process removes unwanted material by controlled chemical corrosion. Selected areas of stainless steel are protected by photoresist mask, while unmasked regions are dissolved by special etching solution.

Stainless steel is widely used across industries for its excellent corrosion resistance. However, its natural chromiumoxide passive film also makes it harder to etch compared with copper or brass. Special pretreatment and matched etchant formulas are required to break down the passive layer and achieve stable, repeatable etching results. The process works well for stainlesssteel thickness ranging from 0.02 mm to 2.0 mm, covering common grades such as 301, 304 and 316L. It is widely adopted in electronics, medical equipment, automotive, newenergy and instrumentation sectors for prototyping, smallbatch trials and massvolume production.

Traditional processing of stainlesssteel often creates burrs, mechanical stress, deformation or heataffected zones. These defects are especially troublesome for ultrathin sheets, dense microholes and finefeature components. Stainless steel etching process avoids these issues and preserves the base material’s inherent mechanical properties.

1. Core Principle of Stainless Steel Etching Process

Stainless steel etching follows the rule of selective protection and selective dissolution.

According to CAD drawings, a patterned photoresist protective mask is formed on the stainlesssteel surface. Areas to be retained are fully covered.

Pretreatment removes the chromiumrich passive film on exposed stainlesssteel surface. The special etchant then triggers chemical reactions and dissolves bare stainlesssteel material.

Stainlesssteel wet etching is isotropic: etchant attacks material both vertically in depth and horizontally sideways. This horizontal erosion is called undercut.

Process engineers calculate the undercut value in advance and add dimension compensation on phototools. This compensation offsets sideerosion and guarantees final part dimensional tolerances.

Without proper mask protection and effective passivefilm removal, consistent stainlesssteel etching cannot be achieved.

2. Full StepbyStep Stainless Steel Etching Workflow

Step 1: DFM Review & Phototool Fabrication

Process engineers analyse customer CAD drawings. They evaluate minimum feature width, holetosheetthickness ratio, feature spacing, throughetch or halfetch depth, as well as stainlesssteel material grade. Expected undercut is calculated, and corresponding dimension compensation is added to phototool files. Unreasonable design requirements are fed back for revision to reduce scrap risk.

Step 2: StainlessSteel Surface PreTreatment

Raw stainlesssteel panels go through alkaline degreasing to remove rolling oil, grease and surface contaminants. Critical acid activation treatment is applied to destroy the stable chromiumoxide passive film. Multistage deionisedwater rinsing and hotair drying deliver a clean, microuniform surface, which ensures reliable photoresist adhesion. Poor pretreatment leads to resist lifting, pattern peeling or uneven etching.

Step 3: DryFilm Photoresist Lamination

Lightsensitive dryfilm photoresist is hotroll laminated onto stainlesssteel surfaces. Doublesided lamination is required for throughetched parts. Lamination temperature, roller pressure and feeding speed are precisely controlled to eliminate bubbles and wrinkles. Trapped air will allow etchant to seep under resist and cause pattern defects. Laminated panels rest for thermal stabilisation.

Step 4: UV Exposure

Compensated phototool films are precisely aligned against resistcovered stainlesssteel panels. Highintensity UV light cures photoresist in transparent graphic zones to form chemicalresistant protective masks. Photoresist under opaque black areas remains soft and soluble. Doublesided exposure is used for highprecision throughetched stainlesssteel components to realise accurate frontback pattern alignment.

Step 5: Developing

Panels pass through dilute alkaline developer solution. Unexposed photoresist dissolves completely and opens clear etching windows on stainlesssteel substrates, while UVcured masking resist stays firmly attached. Automatic optical inspection screens semifinished panels for broken traces, residual resist and blocked microholes.

Step 6: Spray Etching (Core Material Removal)

Stainlesssteel panels travel horizontally through conveyortype spray etching chambers. Specially formulated etchant for stainlesssteel is sprayed onto single or double sides of workpieces under controlled pressure. Operators strictly monitor liquid temperature, concentration, spray pressure and conveyor speed. Etching proceeds until full penetration or target halfetch depth is achieved. Isotropic vertical and horizontal corrosion takes place simultaneously during this stage.

Step 7: Photoresist Stripping

After etching is completed, panels are transferred into hotalkali stripping tanks to remove all cured photoresist masks. Complete stripping prevents resistcaused surface staining. Workpieces receive thorough rinsing afterwards.

Step 8: PostTreatment

Neutralisation eliminates residual corrosive chemicals. A new protective passive film is rebuilt via passivation treatment to restore stainlesssteel’s native corrosion resistance. Optional secondary processes include electropolishing, plating, colour filling, laser marking and panel separation into individual finished parts.

Step 9: Quality Inspection

Videomeasuring equipment verifies dimensional accuracy of holes, slots, contours and flatness. AOI scanning detects pinholes, nicks and pattern distortion. Visual appearance inspection and batchrecord archiving complete the whole workflow.

3. Main Advantages of Stainless Steel Etching Process

Burrfree & stressfree: No mechanical cutting force. Thin and springgrade stainlesssteel parts keep original material properties without deformation.

No expensive hardtooling: Pattern modification only requires updated phototool film, supporting fast prototyping and flexible design iteration.

Excellent for dense microfeatures: Thousands of microholes, fine slots and complex outlines can be formed within one etching cycle. Manufacturing difficulty does not rise significantly with increasing feature quantity.

Supports throughetching and halfetching: Achieves full penetration or controlleddepth partial etching for marking, texturing and structural weakening.

Good batch repeatability: Automated sprayetching lines deliver stable dimensional consistency for highvolume stainlesssteel orders.

4. Process Limitations

Stainless steel etching has inherent isotropic undercut effect. Minimum feature size is limited by sheet thickness. It is most costeffective for thingauge sheets from 0.02 mm to 2.0 mm. Thicker stainlesssteel plates lead to higher production cost. Special pretreatment and stainlesssteelspecific etchant are mandatory for qualified results.

5. Typical Applications of Etched StainlessSteel Parts

Filter meshes, precision gaskets, encoder discs, optical apertures, EMI shielding sheets, spring contact plates, automotive horn grilles, medical nebulizer plates, decorative metal nameplates and various precision stainlesssteel functional components. It covers prototype verification, smallbatch trialrun and massvolume manufacturing.

Conclusion

To sum up, stainless steel etching process is a precision subtractive manufacturing technology for thin stainlesssteel sheets. It relies on photoresist masking and specially matched chemical etchant to realise selective corrosion after breaking the chromiumoxide passive film. Proper surface activation, mask integrity and undercut compensation are critical to obtain highprecision, consistent etched stainlesssteel components.