1 antirust phosphating process
The early application of phosphating process is anti-rust. The iron and steel parts are treated by phosphating to form a phosphating film, which plays an anti-rust role. The anti rust period of the anti rust treatment of phosphating can reach several months or even years (for the oil coating). It is widely used in the process, transportation, packaging and storage and the use of antirust. The antirust phosphating mainly includes three major varieties: iron phosphating, zinc phosphating and manganese phosphating.
The main bath solution of iron phosphating is ferrous phosphate solution, which contains no oxidizing accelerator and has high free acidity. The iron phosphating treatment temperature is higher than 95 C, the treatment time is more than 30 minutes, the phosphating film is more than 10 g / m2, and has the dual functions of rust removal and phosphating. This kind of high temperature iron phosphating is seldom used now because of its slow speed.
Manganese phosphating has the best performance as anti-rust phosphating, and the microstructure of phosphating film is densely packed, which is the most widely used anti-rust phosphating. Addition of nitrate or nitroguanidine accelerator can accelerate the formation of phosphate film. Usually the treatment temperature is 80-100 C, the treatment time is 10-20 min, and the membrane weight is above 7.5 g/m2.
Zinc system phosphating is also a kind of widely used antirust phosphating, usually using nitrate as a promoter, treatment temperature 80~90 C, treatment time 10 ~ 15min, phosphating membrane weight more than 7.5g/m2, phosphating membrane microstructure is generally needle compact heaped type.
Rust prevention and phosphating general process flow:
Oil and rust removal - water cleaning - surface modification activation - phosphating - water cleaning - chromate treatment - drying - greasing or dyeing treatment
The workpiece treated by strong alkali and strong acid will coarsen the phosphating film, and the grain can be refined by surface modification and activation. Zinc system phosphating can be adjusted by oxalic acid and colloid titanium. Manganese phosphating can be activated by insoluble manganese phosphate suspension. Iron system phosphating generally does not need to adjust the activation treatment. The rust resistance of the phosphated workpiece can be greatly improved by chromate sealing. If the workpiece is oiled or dyed, the rust resistance can be increased several times or even dozens of times.
2 wear-resisting and antifriction phosphating process
For an engine piston ring, gear, and refrigeration compressor, a kind of workpiece, it not only bears a load, but also has movement friction, which requires the workpiece to reduce friction and wear resistance. Manganese phosphating film has high hardness and thermal stability, can wear resistance, phosphating film has a good antifriction lubrication. Therefore, it is widely used in piston rings, bearing bearings, compressors and other parts. This kind of anti-wear and friction-reducing phosphating treatment temperature 70-100 C, treatment time 10-20 min, the phosphating film is more than 7.5 g/m2.
In the cold processing industry, such as takeover, drawing, extrusion, deep drawing and other processes, the phosphating film is required to provide antifriction and lubrication performance. The zinc series phosphating is generally adopted. One is that the zinc series phosphating film is saponified to form a good lubricity zinc stearate layer. Two is the low temperature of the zinc system phosphating operation, and can be phosphating at 40, 60, or 90 C. The phosphating time is 4-10 minutes, sometimes even tens of seconds. The weight of the phosphating film should be more than 3 g/m2. The process flow is:
Wear and friction reduction phosphating and friction reduction lubrication phosphating (cold working)
Removing oil and removing rust and removing oil and rust
Cleaning water cleaning water
Manganese phosphide system phosphating
Cleaning water cleaning water
Drying saponification (sodium stearate)
Dryness of grease
Phosphating process for 3 before lacquer
The phosphating treatment before the primer will improve the adhesion of the film and the matrix metal, improve the corrosion resistance of the whole coating system, and provide protection between the process to avoid the formation of two times of rust. Therefore, the primary problem of phosphating before lacquer is that phosphating membrane must have excellent matching with primer, and the antirust of phosphating film itself is secondary, and the phosphating film is meticulous and thin and thin film. When the phosphating film is thick, it will have a negative effect on the comprehensive performance of the paint film. The selection of phosphating system and technology mainly consists of the material of the workpiece, the degree of rust, the geometry of the oil, the time interval between phosphating and painting, the variety and construction method of the primer and the equipment conditions of the related site.
Generally speaking, low carbon steel with higher carbon steel is easy to be phosphated, and the phosphating film is better. For the rust (oxide) workpiece, the workpiece must pass through the pickling process, and the workpiece after pickling will bring a lot of trouble to the phosphating, such as the rusty yellowing between the processes, the removal of the residual acid solution, the roughening of the phosphating membrane and so on. After pickling the workpiece in the zinc, zinc and manganese phosphating before the general surface adjustment treatment.
In the intermittent production situation, the phosphating work must be deposited for a period of time because of the restricted conditions. Therefore, the phosphating film itself has a good antirust property. If the storage period is more than 10 days, medium temperature phosphating should be used generally, such as middle temperature zinc system, medium temperature zinc manganese system, medium temperature zinc calcium system and so on. The thickness of phosphating film should be best at 2.
Between 4.5g/m2. The workpiece after phosphating should be dried immediately, and should not be naturally cooled to avoid rusting in the cracks and welds. If the storage period is only 3-5 days, low temperature zinc series, light iron series phosphating can be used, the drying effect will be better than natural cool drying.
3.1 single chamber spray phosphating process
There is only one spray chamber in the whole pretreatment process. There are several liquid storage tanks under the spray chamber. Different treatment fluids spray the workpiece and flow back to their respective tanks. For example, the first spray defat liquid, when the degreasing liquid goes back to the degreasing tank, closes the valve; then spray water and wash the water, and then closes the water after the washing is finished; the next step is to spray the phosphating solution. This single room treatment can carry out the following process flow. |
