Phosphating treatment of spring

Phosphating treatment of spring
Phosphating is a process to prevent the spring from corrosion during transportation and use. The phosphated spring has corrosion resistance in air, animal and vegetable mineral oil, toluene and other organic solvents. The spring is suitable for zinc phosphate treatment and can avoid hydrogen embrittlement. The phosphating film is thicker than the oxide film, Generally, it is 5 ~ 10 microns. Generally, phosphating has better corrosion resistance than oxidation. Especially, phosphating treatment is suitable for the front process of spring upper protective frame
(1) Spring phosphating process cold and hot water
(1) Removing oil and rust — removing copper — cleaning — phosphating — cleaning — passivation — saponification — soaking film to replace oil — storage
Phosphating process:
Remove oil, rust and oxide scale by shot peening or sand blasting. Used for quenching and tempering springs
2. It can be washed with gasoline and can be phosphated (washed twice or three times) after drying. It is mainly used for fine spring
3. Chemical deoiling naoh100 ~ 150g / L, 20 ~ 70% na2co2 heated to 100 ℃
4. Degreasing and rust removal of barrel is used for stretching spring
This process can be omitted when there is no copper in water and 250 ~ 300 g / L chromic acid and 80 ~ 100 g / L ammonium sulfate
Acid removal by washing with tap water
Manganese iron phosphate tetraphosphate 30 ~ 35 g / L, zinc nitrate 55 ~ 75 g / L, temperature 70 ~ 80 ℃ for 10 ~ 15 minutes, total acidity 48 ~ 60, free acid 2.5 ~ 6.7, sulfate radical ≤ 0.5
5. Washing with tap water
Hexapassivation potassium dichromate (k2cr2o2) 80 ~ 100g / L, 90 ~ 100 ° C
7. Washing with tap water
8. Wash with hot water 90 ~ 100 ℃ for 1 ~ 2 minutes
9. Saponification of 10-20 g / L industrial soap or triethyl oleic acid soap at 50-70 ℃ for 1-2 minutes
10. Change the oil after soaking in water
11. Warehousing
(2) Operation procedures and precautions of spring phosphorus process
(I) before going to work every day, the surface condition of the spring to be phosphated shall be strictly checked, and it is required to be clean and bright. No oil, dirt, rust, copper coating, etc. are allowed
(II) turn on the phosphating tank, passivation tank, hot water tank and heating power supply of saponification tank to ensure that the phosphating bath liquid is 70 ~ 80 ℃, the passivation tank is 90 ~ 100 ℃, the hot water tank is 90 ~ 100 ℃, and the saponification tank is 50 ~ 70 ℃
(III) the material frame used before phosphating is fully sprayed and then loaded with spring. Polyester cotton gloves that must be cleaned or put on the frame shall not have large area or line contact between springs
(IV) the phosphating process requirements should be strictly followed during phosphating, and the temperature should be kept for 10 ~ 15 minutes
(V) after phosphating, the spring should be washed with tap water
(VI) the spring should be kept in the passivation tank for about 1 ~ 2 minutes. After passivation, the spring should be sprayed with tap water
(VII) put the spring into the hot water tank for cleaning for 1-2 minutes, and then put it into the saponification tank for 1-2 minutes, and then send the spring to the coating place or the oil coated part
(VIII) after work, turn off the power supply and clean the workshop carefully
(IX) add manganese iron phosphate and zinc nitrate to the phosphating tank at the ratio of 1:2, the waste potassium dichromate in the passivation tank should be treated in a centralized way, and the saponification tank should be often supplemented with soap or triethyloleic acid soap
(x) if passivation is not required, operation procedure VI can be omitted
(XI) before phosphating, the interval between sand blasting, shot blasting and phosphating should not exceed 4 hours. After cleaning, the spring must be put into the clean material frame
(3) Phosphating quality inspection method
(I) immersion method
3% sodium chloride, temperature 15 ~ 25 ℃, immersion for 2 hours without rust is qualified
(II) drip method
Copper sulfate CuSO 20.5n 40 mg, sodium chloride 10% 20 mg, sulfuric acid 0.1N 0.8 mg
The longer the yellowing time is, the better the quality is. The one without discoloration within 3 minutes is qualified
(III) drip method II
Copper sulfate CuSO4, sh2066 g / L, sodium chloride 32.5 g / L, hydrochloric acid HCl 1:101.2 g / L, drip for more than 3 minutes without yellowing are qualified http://www.888th.com.cn
(IV) immersion method
Copper sulfate 5% solution, immersion for 1 minute, the workpiece surface does not appear yellow is qualified
While inspecting the phosphating quality of the workpiece, the total acidity, free acid and acid radical parameters of the phosphating bath solution must be tested regularly to ensure the daily phosphating quality of the workpiece