Beyond aesthetics, low roughness makes the material less susceptible to corrosion and easy to clean. There are several surface treatments whose main:

The mechanical polishing and electropolishing (or tube is immersed in the electrolytic bath room). the latter technique to polish complex shapes.

Ra is a unit of measurement of the state of polished and made ​​expressed in microns (micro-meter). The Ra is equal to the arithmetic average of the absolute value of Y axis between each point of the profile and laligne average.

Add “straightness” the total variance on the correctness of a tube length L does not exceed 0.0015. L. any local straightness deviation over a length of 1M tube must be less than 3 mm according to EN 10216-5 NF (see photo test straightness achieved at Alco on Bench Mitutoyo)