Square steel tube has a wide application in many areas like：Engineering construction, door or window framing, furniture, exercise equipment’s, frames for canvas or plastic sheeting in deck-chairs, railings, etc.

The square shape makes it easy to assemble and transport as the tubes can be stacked easily without danger of rolling off.
Its pickling passivation operation steps are divided into the following steps:

1. The preparing work
2. Chemical degreasing
3. Hot water rinse
4. Passivation
1) passivation using slot in the pool, passivation solution formulation and immersion time in accordance with relevant regulations.
2) passivation channel is made of steel plate, with the lining spread anti-acid plastic.
3) soaking in the groove, attention should be paid to the location of the placement, avoid the air left in the tube.
4) in the soaking steps should move up and down or flip side tube, the inner cavity solution change constantly, in order to improve the effect. When necessary, take out the square tube, soaked in water after flushed by the stream.
5. Inspection
6. Protection
1) For the square steel tube the outer surface needs to be painted, it is carried out according to the coating requirements.
2) For the tube passing through the inspection, sealing with plastic plug, in three fabric bandage to protect, and identified finally.