Threaded fasteners mainly composed of six core elements?
Phosphating fastener process: the total acidity is too high will make the film is too thin, the total acidity is too low will make the film loose rough. The acid ratio refers to the relationship between the free acidity (Tb) and the total acidity (Ta). Free acidity is too high, and the role of iron and steel parts will be a lot of hydrogen, so that the interface layer of phosphate is not easy to saturate, resulting in the formation of difficult nuclei, thick crystalline layer, loose holes, corrosion resistance, and phosphating time Prolonged; free acidity is too low, phosphating film is thin, even without phosphating film generation.
Solution main component low: add the main liquid. Acid ratio is not correct: free acidity is too high, can add manganese carbonate and other regulation: the total acid is too low, can add the main agent regulation, total acid control at 85 points or more. Poor solution composition: improved phosphating solution formula, the use of PL-VM phosphating solution.
The use of PL-VM phosphating solution, the solution parameters of simple adjustment, less sediment, the workpiece hanging ash, the film crystal fine honey, the resistance to neutral salt spray time can be improved, the workpiece by the neutral salt spray test after a small degree of corrosion.
Self-phosphating solution composition control is not good, the solution is difficult to adjust, precipitation, the workpiece hanging ash, in the phosphating process parts easily lead to corrosion.
Causes and Countermeasures of Poor Corrosion Resistance of Phosphating Fasteners
- the solution composition ratio is poor: to improve the phosphating liquid formula, the use of PL-VM phosphating solution.
- acid ratio is not correct: free acidity is too high, can add manganese carbonate and other regulation: the total acid is too low, can add the main agent regulation, total acid control at 85 points or more.
- the main components of the solution is low: add the main liquid.
- the main components of the solution is not correct: solution Shenqing, the tank temperature control at 95 ℃ or so.
- phosphating time is too short: phosphating time control in 10 ~ 15min.
- the solution of high Fe2 + content: plus hydrogen peroxide and other oxidants to adjust the Fe2 + content, or replace the bath.
- there are oxides in the solution: replace the bath, or to strengthen the workpiece before the pickling cleaning.
- the former treatment is not clean: the use of sandblasting or fasteners to maintain a good surface before the phosphating conditions.
- loading too much: the use of hanging or reduce the load, so that the fasteners to maintain a certain gap, so that it can fully respond.
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