Shandong iron series phosphating solution

1. Process flow

1.1 Degreasing (alkaline) → washing → rust removal → phosphating → washing → drying

1.2 Degreasing (acid) → rust removal → washing → phosphating → washing → drying

1.3 Oil stain removal → water washing → phosphating → water washing → drying

2. Solution preparation (1 ton)

The weight ratio of phosphating film agent to water is 1:9, that is, 100kg of phosphating solution and 900kg of water in 1 ton of working fluid. The pH value of the working solution is 3-4.

3. Performance indicators

4. Detection method

4.1 Total acidity (points)

Take 10 ml of working solution in a conical flask and add 3-5 drops of phenolphthalein indicator. Titrate the above solution with 0.1M sodium hydroxide standard solution from colorless to red. The amount (ml) of 0.1M sodium hydroxide standard solution is called the total acidity point.

4.2 Free acidity (points)

Take 10 ml of working solution into the conical flask, and add 2 to 4 drops of bromophenol blue indicator. Titrate the above solution with 0.1M sodium hydroxide standard solution from yellow to blue. The amount (ml) of 0.1M sodium hydroxide standard solution is called the free acidity point.

5. Increase adjustment (1 ton)

After a period of use, the phosphating working solution will lose its activity. When the total acidity is normal but the free acidity is too low, a phosphate coating agent can be added.

Theoretical calculation: Adding 5 kg of phosphating agent can increase the free acid content by 1 point, and 4.2 kg can increase the total acid content by 1 point.