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The treatment aqueous liquid (DacrI Dip) used for Dacr treatment is the dispersive aqueous solution composed of Zn chip, anhydrous Cr acid, glycol etc. After the objects which will be treated is put into the treatment liquid for soaking and will be dried, it is heated in drying oven to 300 ℃ or so, to make Cr with 6 valence to be reducted by glycol etc organic matter to generate insoluable and amorphous nCrO3 , mCr2 O3 as a binder, it will mutually be combined with Zn chips which have several tens stratums to form an envelope, meanwhile the anhydrous Cr acid in Dacr treatment liquid makes the metal material surface oxidation to form a chemical binding to generate strong adhesive force.
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The anti-rust mechanism of Dacr treatment envelope is:
1 、
Controlled galvanic protection of Zn particles
2 、
Cr acid makes the metal surface to form dense passivation, which is not easy to be corroded.
3 、
Shielding action of Zn chip and Cr compound
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So, Dacr has unable comparable, superior corrosion-resisting properties compared with other surface treatments. The part, which has been treated by Dacr, is cooled by liquid N2 to make it to break. Below is a fracture photograph taken by a high multiplying power scan electronic microscope. |
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Fracture photograph of
Dacr treatment free envelope (X70000) |
Fracture photograph of
Dacr treatment envelope (X2500) |
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