Frequent problems in metal phosphating treatment and countermeasures

Metal phosphating is one of the common measures for metal surface treatment. However, in the process of operation, metal phosphating is prone to defects and affects the treatment effect, so metal phosphating often has defects and solutions.

1. The phosphating part returns to rust.

Cause: The free acidity is too high, the Fe2+ ion concentration is too high, and the phosphating time is insufficient.

Solution: Adjust the acid ratio, clear the tank or treat with hydrogen peroxide to prolong the treatment time.

2. The film is uneven and has flow marks.

Cause: The oil removal is not clean, the phosphating temperature is low, and the workpiece has a passivation layer.

Solution: Strengthen degreasing, raise temperature, and pickle.

3. The film has blank spots.

Cause: The phosphating temperature is too low, the workpieces are placed too densely or overlapping, and the acid ratio is too large.

Solution: Increase the temperature, increase the gap between the workpieces, and adjust the acid ratio.

4. Hang the ash.

Cause: There is sediment in the bath, the phosphating solution is not cleaned, and the C content of the phosphating solution is too high.

Solution: Remove the precipitate, re-phosphate after pickling, adjust the amount of phosphating solution C.

5. The film is coarse.

Cause: The Fe2+ ion content is too high, the phosphating solution C content is high, and the temperature is too high.

Solution: Change the bath or treat with hydrogen peroxide, adjust the amount of phosphating solution C, and cool down.

6. The film appears colored red spots.

Cause: The free acid is too low, the phosphating solution C content is too high, and the material contains heavy metals.

Solution: Add the stock solution, delay consumption or add urea to analyze the material.

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