title = "Electropolishing for Stainless Steel and Alloys"

content = """
Electropolishing is an electrochemical metal removal process that smooths and brightens metal surfaces by selectively dissolving microscopic peaks and asperities from the workpiece surface. At Ridgecrest Metalworks, electropolishing is applied primarily to stainless steel components requiring enhanced corrosion resistance, hygienic surfaces, or improved aesthetic finish.

The process is essentially the reverse of electroplating. The part to be polished is connected as the anode in an electrolytic cell. The electrolyte is typically a mixture of phosphoric acid and sulfuric acid at elevated temperature (60–80 °C). Cathodes are lead or stainless steel plates. When current passes, metal ions dissolve from the anode (the part) at a rate inversely proportional to local current density. Peaks and high points on the surface have higher current density and dissolve faster, while valleys dissolve more slowly, resulting in a net smoothing effect.

Benefits of electropolishing on stainless steel include:
- Surface roughness reduction: Ra can be improved from 0.8–1.6 µm to 0.1–0.4 µm or better
- Removal of the deformed (Beilby) layer left by mechanical polishing, exposing clean crystalline structure
- Enhanced passive layer formation: chromium-rich passive film improves corrosion resistance significantly
- Removal of embedded ferrous contamination and weld heat tint
- Elimination of micro-crevices that harbor bacteria, important for food-grade and pharmaceutical components

Process parameters requiring control include current density (typically 3–10 A/dm²), bath temperature, acid concentration, and immersion time. These are defined in process sheets specific to alloy grade (304, 316L, 17-4 PH, etc.). Parts must be thoroughly cleaned and degreased before processing; oil or oxide contamination causes uneven electropolishing or pitting.

Post-electropolishing, parts are rinsed in clean water, passivated if specified, and dried. Visual and roughness inspection confirms process effectiveness. White etching, streaking, or pitting indicates process upsets requiring root cause analysis. Bath chemistry is monitored daily; spent electrolyte is hazardous waste and requires licensed disposal. Operators wear full acid-resistant PPE including face shields, chemical-resistant gloves, and apron throughout the process.
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