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 HOME > Business > Impregnation |
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Impregnation is not usually used in our daily lives and so strange that it is hard to find in a dictionary. The closest meaning to its Korean equivalent is "impregnation," which means pregnancy, fertilization, infusion, infiltration, saturation, and inspiration. "Impregnation" is a set of processes that remove remaining air from pores inside causing leak of liquid or gas via porosity and defects of the product porosity and infuse a solution(impregnation solution in general) to seal those pores in the course of testing for internal seal of finished parts when producing sealed products.
Now, most of metal products are generally porous, containing various defects inside. in the case of aluminum alloy die-cast products, aluminum alloy faces 5% or so shrinkage after changing state from liquid to solid alone while freezing cooling, causing shrinking pores. Also, leakage of hydrogen gas in the solution causing foams, making pores.
Shrinkage while freezing and leak of gas are related to each other, causing various defects such as pipe, large pores, small pin holes, vertical cracks, shrinking porous matters. Usually, these defects are likely to happen around the vertical side of crystals, which are clustered in hydrides and oxides (Al2O3, Al2O3MgO, SiO₂etc.).
So, in the case of die castings with these defects penetrating both sides, pressure difference between the two sides causes leak.
Impregnation to seal these penetrating defects can make products, once discarded as defective products, become normal ones, increasing productivity and saving production cost.
Also, in case of electric or chemical casting for castings and sintered products, pre-coating and coating solution may leak in from exposed defects, causing swelling and corrosion of the coated layer. So be sure to conduct impregnation in advance to seal exposed defects.
It is used not only to treat the plating base, but also to prevent corrsion of pores.
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 Aluminum Alloy
Zinc Alloy
Magnesia Alloy
Copper Alloy
Lead Alloy
Iron Alloy
Graphite Alloy |
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Aircraft Parts
Auto parts (Engine Block, Cylinder Head, Manifold, Carburetor, Mission Case Water Pump, Radiator, Brake Drum & Disk, Air Compressor…)
Gas meter parts
Flow meter parts
Pipe, Pipe Joint
Valves
Anything that needs pressure and moisture resistance
Recently, aluminum alloy has become increasingly popular in a wide range of areas. This is because specific gravity of aluminum alloy is 1/3 lighter than iron and copper alloy, which makes products far lighter, its melting point is lower enough to allow for continuous casting and its easier mechanical process is effective to mass production, and its thermal conductivity is excellent. As a result, aluminum alloy is often replacing other metals that were used before.
The use of zinc alloy is growing, because, with a low melting point, it allows for continuous casting and is good for mass production. To make product lighter, magnesia alloy is better than aluminum alloy and therefore widely used for aircraft parts. These metals, however, are chemically active, so they are likely to cause defects. Lately, the progress of powder metallurgy has made it possible to produce machine parts without mechanical working of metal powder by pressurized molding and sintering, but unlike products made of general steel materials (cast steel excluded), many of them are porous. Any product having the above defects needs impregnation.
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Mechanical working does not cause new internal defects on the surface, or defects, if any, are not penetrating up to the other end and do not cause leak due to pressure, apply impregnation to the material as it is before mechanical process. |
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In general, mechanical process causes new internal defects on the surface. Therefore, if there is a leak on the working surface, or adverse effects on the surface process (coating, plating, etc.) are likely after mechanical working, do impregnation after mechanical working. |
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Defects on the surface of the product are likely to cause swelling or exfoliation after plating or coating. Also, infiltrating surface treatment solution into pores may cause corrosion, so impregnation is conducted before surface working in most cases. |
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Impregnation may be performance after surface working if pin holes are considered likely to cause corrosion during the surface working, although surface processing solution does not infiltrate into the pores and no corrosion occurs, even after surface working. Sometimes, however, surface color may change to some degree, so it is recommended to check in advance. In general, regardless of whether organic or inorganic, surface working after impregnation can raise the effect of impregnation. |
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