What are the steps for pickling 304 stainless steel pipes?

Operation steps for pickling 304 stainless steel pipes.

1. Pipe ready

2. Chemical degreasing

(1) The chemical oil removal adopts the immersion method in the tank, and the oil removal tank is made of steel plate, with PVC or polyethylene laid on the inner wall.

(2) Chemical degreasing treatment uses 12-15% nitric acid (by volume) at a temperature of 40 ℃ to 60 ℃ for 2-4 hours.

(3) When soaking 304 stainless steel pipes in the tank, attention should be paid to their placement to avoid leaving air inside the pipes.

(4) During the soaking process, the tube should be moved up and down or flipped, and the internal solution should be constantly replaced to improve the effect. If necessary, remove the tube, rinse with water and gas, and then soak.

(5) Chemical degreasing until the surface of the pipe fittings is completely wet.

3. Hot water flushing

(1) Remove the 304 stainless steel sanitary pipe after oil removal from the oil removal tank and soak it in a hot water tank at around 40 ℃~60 ℃ for rinsing for 5-20 minutes.

(2) The hot water tank is made of steel plate, and the inner wall is covered with polyvinyl chloride or polyethylene.

(3) The chloride ion content in water is less than 25ppm.

4. Rinse with water.

(1) Use pressure water (pressure P ≥ 0, 1Mpa) to rinse the pipes that have been washed with water.

(2) The chloride ion content in water is less than 25ppm.

5. Passivation

(1) Select the passivation solution formula and soaking time according to Tables 2 and 3.

(2) Produce passivation groove steel plates with acid resistant plastic on the inner walls.

(3) When soaking in the tank, pay attention to the placement to avoid air inside the tube.

(4) During the soaking process, the pipe fittings should be moved up and down or flipped, and the internal solution should be constantly replaced to improve the effect. If necessary, the pipes should be removed, washed with water and gas, and then soaked.

6. Drying

After passivating the 304 stainless steel sanitary pipe, dry it with clean compressed air or nitrogen, and there must be sufficient time (at least 2 hours) for natural passivation in the air.

7. Inspection

After passivation of 304 stainless steel sanitary pipes, self inspection and mutual inspection should be conducted, and then submitted to quality inspection personnel for acceptance as required.

8. Protection

(1) Pipe fittings that require painting on the outer surface shall be painted according to the painting requirements.

(2) The pipes that pass the inspection shall be sealed with plastic plugs, wrapped with three proof cloth for protection, and marked.