Phosphating is a process to prevent springs from corroding during transportation and use. Phosphated springs have anti-corrosion ability in the air, animal and vegetable mineral oil and organic solvents such as toluene. The spring is suitable for zinc phosphate treatment to avoid hydrogen embrittlement. The phosphating film is thicker than the oxide film, generally 5-10 microns. Generally, phosphating has better corrosion resistance than oxidation. In particular, the phosphating treatment is suitable for the front process of the spring protection frame.
(1) Spring phosphating process cold water and hot water
(1) Remove oil and rust-remove copper-cleaning-phosphating-cleaning-passivation-cleaning-saponification-immersion film replacement oil-storage
Serial Number Name Technical Requirements Remarks
1. Oil removal 1. Shot blasting or sand blasting to remove oil, rust and oxide scale for quenching and tempering springs
2. Gasoline washing, phosphating after drying (can be washed two or three times) Mainly used for thin springs
3. Chemical degreasing NaoH100～150g/L 20～70%Na2CO2 heated to 100℃
4. Rolling barrel to remove oil and rust, used for tension spring
Second, copper removal 250～300g/l of chromic acid, 80～100g/l of ammonium sulfate, add water, this process can be omitted when there is no copper
Three cleaning tap water rinse to remove acid
4. Phosphating Manganese iron phosphate 30～35g/l, zinc nitrate 55～75g/l, temperature 70～80℃, hold for 10～15 minutes, total acidity 48～60, free acid 2.5～6.7 sulfate ≦0.5
Five cleaning tap water rinse
Six Passivation Potassium dichromate (K2Cr2O2) 80～100g/L 90～100℃
Seven cleaning tap water rinse
8. Washing with hot water at 90～100℃ for 1～2 minutes
9. Saponification 10～20g/L industrial soap flakes or triethyl oleic acid soap 50～70℃ 1～2 minutes
Ten oiling, water immersion film volume, oil change
(2) Operating procedures and precautions for spring phosphorus process
(I) The surface condition of the spring to be phosphated should be strictly checked before going to work every day, and it is required to be clean and bright. No oil, dirt, rust, copper plating, etc. are allowed.
(Ⅱ) Open the phosphating tank, passivation tank, and hot water tank. The saponification tank heating power source ensures that the phosphating tank liquid is at 70-80°C, the passivation tank is 90-100°C, the hot water tank is 90-100°C, and the soap tablet tank is 50-70°C.
(Ⅲ) The material frame used before phosphating is fully spray-washed and then loaded with springs. The polyester-cotton gloves must be cleaned during frame mounting. There should be no large area or line contact between the springs.
(IV) Strictly implement the phosphating process requirements during phosphating, and keep the temperature for 10-15 minutes.
(Ⅴ) After phosphating, the spring should be fully rinsed with tap water.
(VI) The spring is kept warm in the passivation tank for about 1 to 2 minutes. After passivation, it needs to be fully sprayed with tap water.
(Ⅶ) Put the spring into the hot water tank for cleaning for 1 to 2 minutes, then put it in the saponification tank for 1 to 2 minutes, and then send it to the coating place or oiling and then to the coating place.
(Ⅷ) After get off work, turn off the power and clean carefully to ensure that the workshop is tidy.
(IX) Add manganese iron phosphate and zinc nitrate to the phosphating tank at a ratio of 1:2, the waste potassium dichromate in the passivation tank should be treated in a centralized manner, and the saponification tank should be frequently supplemented with soap flakes or triethyl oleic acid soap.
(Ⅹ) If passivation is not required, the operating procedure Ⅵ can be omitted.
(Ⅺ) The interval between sandblasting, shot blasting and phosphating of the spring before phosphating shall not exceed 4 hours. After cleaning, the spring must be placed in a clean material frame.
(3) Phosphating quality inspection method
(Ⅰ) Soaking method
3% sodium chloride NaCl, temperature 15～25℃, immersion for 2 hours without rust is qualified.
(Ⅱ) One drop method
Copper sulfate CuSO20.5N 40 mg Sodium chloride Nacl 10% 20 mg, sulfuric acid. 0.1N0.8 mg.
The longer the yellowing time after instillation, the better the quality, and the one that does not change color within 3 minutes is qualified.
(Ⅲ) The second drip method
Copper sulfate CuSO4, SH20 66 g/l, sodium chloride NaCL 32.5 g/l, hydrochloric acid HCL 1:10 1.2 g/l, instillation for more than 3 minutes without yellowing is qualified.
(Ⅳ) Soaking method
Copper sulfate 5% solution, no yellow on the surface of the workpiece after immersion for 1 minute is qualified.
While inspecting the phosphating quality of the workpiece, the total acidity, free acid, and acid radical parameters of the phosphating bath must be regularly tested to ensure the daily phosphating quality of the workpiece.