Stainless Steel Electropolished Pipe

Dimensions Chart, 15A-800A (Unit=mm)

Nominal Size	Outside  Diameter	Wall Thickness t(t1, t2)		Type of Pipe		Surface Treatment / ID Polishing Method
		5S	10S	Seamless	Welded (ID Bead Cut)
15A	21.7	1.65	2.1	◎		Longitudinal
20A	27.2	1.65	2.1	◎	◎	Longitudinal
25A	34.0	1.65	2.8	◎	◎	Longitudinal
32A	42.7	1.65	2.8	◎	◎	Longitudinal
40A	48.6	1.65	2.8	◎	◎	Longitudinal
50A	60.5	1.65	2.8	◎	◎	Longitudinal
65A	76.3	2.1	3.0	◎	◎ (YES)	Spiral / Longitudinal
80A	89.1	2.1	3.0	◎	◎ (YES)	Spiral / Longitudinal
100A	114.3	2.1	3.0	◎	◎ (YES)	Spiral / Longitudinal
125A	139.8	2.8	3.4		◎ (YES)	Spiral
150A	165.2	2.8	3.4		◎ (YES)	Spiral
200A	216.3	2.8	4.0		◎ (YES)	Spiral
250A	267.4	3.4	4.0		◎ (YES)	Spiral
300A	318.5	4.0	4.5		◎ (YES)	Spiral
350A	355.6	4.0	4.8		◎ (YES)	Spiral
400A	406.4	4.2	4.8		◎ (YES)	Spiral
450A	457.2	4.2	4.8		◎ (YES)	Spiral
500A	508.0	4.8	5.5		2  (YES)	Spiral
550A	558.8	4.8	5.5		2  (YES)	Spiral
600A	609.6	5.5	6.4		2  (YES)	Spiral
800A	812.8	6.4	7.9		2  (YES)	Spiral

●"2" means "two seams" welded pipe.

Dimensions Chart, 1/8"-6" (Unit=mm)

Nominal Size	Outside  Diameter	Wall Thickness	Type of Pipe		Surface Treatment / ID Polishing Method
			Seamless	Welded (ID Bead Cut)
1/8”	3.18	0.7	◎
1/4”	6.35	1.0	◎
3/8”	9.52	1.0	◎
1/2”	12.7	1.0，1.24	◎
5/8”	15.88	1.24，1.65	◎
3/4”	19.05	1.24，1.65	◎
1”	25.4	1.65	◎	◎ (Option)	Longitudinal
1-1/4”	31.8	1.65	◎	◎ (Option)	Longitudinal
1-1/2”	38.1	1.65	◎	◎ (Option)	Longitudinal
2”	50.8	1.65	◎	◎ (Option)	Longitudinal
2-1/2”	63.5	1.65	◎	◎ (Option)	Longitudinal
3”	76.2	1.65	◎	◎ (Option)	Spiral / Longitudinal
4”	101.6	2.11	◎	◎ (Option)	Spiral / Longitudinal
5”	127.0	2.77		◎ (Option)	Spiral
6”	152.4	2.77		◎ (Option)	Spiral

Product Type and Grade

 

Specification of Chemical composition

 

Tolerance of Dimensions

Description	Size	Tolerance
Outside Diameter	<38.1mm	±1%
	≥38.1mm, <88.9mm	±1%
	≥88.9mm, <139.8mm	±1%
	≥139.8mm	±1%
Wall Thickness	<2.1mm	±10%
	≥2.1mm	±12.5%
Length	6000mm or 4000mm	As mill Standard

 

Manufacturing Process of AP, MP (BA) and EP

Grade Of Finish of Pipes	AP Finish	MP (BA) Finish	EP Finish
ID bead-cut, bead removed	Option	YES	―
ID mechanical polishing	NO	YES	―
RO Water Cleaning	YES	YES	―
DI Water Cleaning	NO	YES	YES
Chemical Passivation	YES	YES	YES
Clean Room, Class 1000 Cleaning and Bagging	Option	YES	YES
Double Sleeve Bagging	Option	YES	YES

 

Inspection Criteria

Grade Of Finish of Pipes	ID Surface Roughness, Ra	Oil Residual	Particle Level
AP Finish	—	＜0.1mg/ft²	―
MP (BA) Finish	OD ≤2” ：Ra≤0.38μm	＜0.1mg/ft²	>0.1μm, Max. 5PC
	OD 2.5”-6” ：Ra≤0.5μm
EP Finish	OD ≤4” ：Ra≤0.25μm	＜0.01mg/ft²	>0.1μm, Max. 1PC

Electropolishing
Electropolishing is a process that uses a metal workpiece as an anode and performs electrolysis in a suitable electrolyte to selectively remove its rough surface and improve the surface finish, it is also called Electrochemical or anodic polishing.

Theory
During electropolishing, current flows on the surface of the metal product as the anode, which will form an oxide film, a salt film, or an oxygen adsorption layer on the surface, so that the metal dissolution rate of the anode drops sharply, that is, in a passive state. But this passivation film layer may be dissolved in the electrolyte, and the anode is reactivated. At a certain current density, metal passivation and metal dissolution proceed alternately.

Electrolyte
The electrolyte usually uses phosphoric acid as the main component, and it also needs to add certain oxidants (such as sulfuric acid, chromic anhydride, etc.). Without electricity, the electrolyte should have no significant corrosive effect on the metal being polished. It also requires that the electrolyte has a high solubility for the anode dissolution product and is easily removed. In addition, the electrolyte is required to have good stability, low cost and low toxicity. If necessary, a small number of organic substances (such as glycerin, methylcellulose, etc.) can be added to the electrolyte as a corrosion inhibitor. Use perchloric acid-acetic acid electrolyte for electropolishing to obtain a high-finish surface.

Process
After being energized, a polarized film is formed on the surface of the polished metal, allowing metal ions to diffuse through this thin flag. The current density of microscopic and macroscopic bumps or rough spots on the surface and the burr area is greater than the rest of the surface, and it dissolves at a faster rate to achieve the purpose of leveling and deburring. By prolonging the polishing time, and increasing the polishing temperature and current density, a bright surface can be obtained.

Mechanical Polishing
Mechanical Polishing is a process of grinding the surface of the metal using an abrasive belt and mechanical tools at multiple stages to achieve a desired smooth surface and roughness value, meanwhile, it alters the microstructure of the surface.
Stainless steel tubing is polished mechanically to pass through a set of abrasive wheels and tapes with a polishing machine, with polishing paste to improve polishing efficiency, finally, this process makes the desired polishing level using the different grinding belts to remove the surface layer.
There are Dry and Wet mechanical polishing for selecting, wet style is a better option.

Mechanical Polishing Vs. Electropolishing
Mechanical Polishing and Electropolishing are the main methods to polish stainless steel tubing, mechanical polishing performs well for general industries, when a higher polishing level is required, like in the pharmaceutical and semiconductor industries, Electropolishing has its advantages.

• Improve Cleanability
• Enhance Durability
• Improve Sterility
• Increase Corrosion Resistance

Mechanically polished surfaces retain the basic alloy composition with only slight depletion of the other alloy elements, whereas electropolished surfaces contain essentially only chromium and iron, and no stress resides.