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Surface treatment AP/MP/BA/EP

October 28, 2023

AP: pickling pipe (anneal treatment & passivation) / (acid pickling).

MP: mechanical grinding process or mechanical polish (mechanical polish).

BA: bright passivation treatment or bright annealing (bright anneal treatment)/(bright annealing).

EP: electrolytic grinding treatment.


Stainless steel BA tube - bright annealed tube (vacuum bright annealed tube)
It is the abbreviation of atmosphere protection heat treatment (bright annealed), also known as: stainless steel BA pipe, clean pipe, bright annealed pipe, seamless pipe, gas line tube, high purity gas line, tube.

Material: 304, 316L.

Standards: ASTM A249, A269, A270, 3A and BPE standard, JIS G3447. G3459.

Forming: mainly multi-roller cold rolling, the size can reach 0.2%, and the inner surface finish Ra<0.45 um.

Features: accurate dimensions, smooth surface, overall cleanliness, inner surface unpolished is better than polished finish.

Raw materials: meet ASTM A269 standards, double furnace steel ingots can be used for special requirements.

Manufacturing: cold rolling + fine drawing, dimensional accuracy reaches about 0.05mm, inner surface Ra is about 0.4 microns.

Heat treatment: bright solid solution (annealing) under the protection of reducing atmosphere.

Cleaning: use SC2286 cleaning agent for ultrasonic Ultrasonic cleaning. That is to say, it must be degreased and degreased.

Inspection: eddy current non-detection + water pressure, etc.

Finishing: straightening + sizing + polishing.

Packaging: Inkjet coding + PE bag + cap + shock-absorbing packaging + Gechen packaging + protection.

Purpose: Special gas or liquid transportation, and also the base material of EP pipes.

Applicable industries: biopharmaceuticals, electronic clean workshops, high-purity gases, high-demand clean laboratories, liquid crystal displays, solar photovoltaics, polysilicon and other fields. Semiconductor industry, liquid crystal industry, pharmaceutical industry, instrumentation system, compressed air, ultra-high purity gas, chemical system, WFI system and other gas pipeline systems or clean rooms or equipment with high-purity and ultra-high-purity requirements.


EP process: based on high-quality BA pipes, the inner surface is electrochemically polished, then purified with high-purity water, and packed with nitrogen.

Diameter control: tolerance ±0.02mm (0.1%).

Length control: tolerance ±0.05mm.

Straightness: no more than 0.1mm/m.

Surface roughness: EP tube Ra≤0.15μm.

Concentricity control: tolerance ±0.01mm.

Mechanical property control: Hardness HRB (75~580), strength δb and elongation Ψ can be adjusted and controlled.

Heat treatment: solid solution treatment in reducing atmosphere.

Packaging: double bagged and capped.


EP: bright annealing--->non-destructive testing--->chemical polishing---->electropolishing.

BA: bright annealing--->non-destructive testing--->one cleaning.

CP/AP: heat treatment--->non-destructive testing--->chemical polishing.