double wall tube Zinc plated PA 12 coating brake metal tube, brakeline

Some technical parameters as reference, pls check below:

4.1 Steel tube classify as per table 1.

4.2 Surface coating classify as per table 2

4.3 Zinc plating surface passiviation as per table 3

4.4 Requirements & method

surface quality

Under visual inspection of natural light, the appearance of corrosion coating should be basically the same, allowing the color difference that does not affect the quality of the product. The surface of steel tube coating should not be leakage plating, leakage coating, blistering, shedding, crackle and no sharp accumulated nodule≥1.5mm . Both parties shall provide the approved standard samples when necessary.

4.5 Coating , coating thickness and max.OD

Table 4 coating thickness

5.4 Adhesion strength

  5.4.1 zinc layer adhesion strength

For the outer diameter less than 8.00 mm, the bent diameter is 3 times of OD; for the tube diameter is greater or equal to 8.00mm, the bent diameter is 6 times of OD. Bending 360 degree along the mandrel. Use fiber adhesive tape to paste the bent outside surface, carefully remove all the air bubbles, stay for 10S, and then remove the tape slowly and evenly, and no zinc removal and peeling shall occur after the test.

5.4.2 coating adhesion

5.4.2.1 bending test: For the outer diameter less than 8.00 mm, the bent diameter is 3 times of OD; for the tube diameter is greater or equal to 8.00mm, the bent diameter is 6 times of OD; bending 360degree along the mandrel. The coating show no cracking or wrinkling after test.

5.4.2.2 Grid test: cut 3.2mm square lattice cross shadow line on the tube surface at least 180° circumference and 25mm tube length, adhesive tape paste the cut surface, and carefully remove all air bubbles, stay for 10S, and then slowly and evenly remove the tape, no chips or peeling phenomenon after the test.

5.5 Corrosion resistance

5.5.1 Neutral salt spray test

5.5.1.1 zinc plated tube

       As per GB/T 10125 , neutral salt spray test method, after the test, shall conform to the requirement showed in table 6.

Note: passivation film of plating layer shall be good and no damage before salt spray test, withstand 24 hours room temperature aging treatment.

5.5.1.2 zinc plating +organic coating

   The test samples shall be prepared as per below graph 1. According to neutral salt spray test method stipulated by GB/T 10125, after the test, It shall conform to the requirements of table 7.