Electrolytic polishing is mainly used in industries such as semiconductors, biopharmaceuticals, and photovoltaics that do not tolerate any pollution in high-purity pipelines. Its benefits are very practical: the inner wall of the produced pipeline can be smooth to a few micrometers, impurities cannot hang on, and cleaning is also easy; At the same time, electrochemical treatment will form a dense oxide film on the surface, which has much stronger corrosion resistance than ordinary acid washing or mechanical polishing, and has a longer lifespan when used in corrosive media.
Although electrolytic polishing of pipelines is slightly more expensive than ordinary processes, it is actually more cost-effective in the long run for production lines with strict requirements - because there are fewer failures, less maintenance, and guaranteed product yield.
Simply put, it solves the two core problems of "cleanliness" and "durability".
The selection of electrolytic polishing clean pipes mainly depends on three aspects: where to use them, materials and standards, and the matching of pipe fittings and valves.
- First, look at the application scenario
Semiconductors and biopharmaceuticals have the highest requirements. Semiconductors typically require Ra ≤ 0.2 μ m or even lower, and have strict criteria for particle release and metal ion precipitation, generally following SEMI F20 or F57 standards.
Biopharmaceuticals place greater emphasis on the quality and hygiene of the passivation layer on the inner wall, commonly using ASME BPE standards. The surface is divided into mechanical polishing (MP) and electrolytic polishing (EP), with grades ranging from SF1 to SF4, with smaller numbers resulting in smoother surfaces. EP can generally achieve SF1/SF2 grades.
The requirements for photovoltaics and fine chemicals are not as extreme, but EP tubes are still preferred for highly corrosive media. However, the roughness can be relaxed to Ra ≤ 0.4 μ m, making it more cost-effective.
- Material and brand
The mainstream is 316L (low-carbon stainless steel), but in strong corrosion or ultra-high purity scenarios, specialized high-purity materials such as 316L VIM/VAR (vacuum remelting) or SUS 316L EP are used, with finer grain size and fewer inclusions.
If the medium contains chloride ions or the temperature is higher, it may be necessary to use EP tubes made of nickel based alloys (such as C276), but the cost is several times higher and usually only used in special process sections.
- Pipe fittings, valves, and system matching
EP pipes should be equipped with EP grade elbows, tees, diaphragm valves, or VCR fittings, otherwise even if the pipeline is clean, one valve may bring particles in.
The semiconductor industry commonly uses VCR face sealed joints, combined with EP tubes, to achieve zero metal to metal leakage; Biopharmaceuticals often use sanitary grade chucks, and the inner walls also need EP treatment to ensure that there are no dead corners during CIP/SIP.