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Dacromet vs. traditional electrogalvanizing technology

Posted on 2018-11-12
Dacromet coating, also known as zinc flake coating, has the advantage that the latter cannot be achieved compared to conventional electro galvanized and hot dip galvanizing techniques. Zinc flake coating has the following advantages:

#1. Extraordinary corrosion resistance

The controlled electrochemical protection of zinc, the shielding effect of zinc/aluminum sheets and the self-repairing effect of chromate make the Dacromet coating highly resistant to corrosion when the Dacromet coating is tested in the neutral salt spray. It takes about 100 hours to etch the coating 1um, which is 7-10 times better than the traditional galvanizing treatment. The neutral salt spray test can last for more than 1000 hours (coating with a thickness of 8um or more), and some even higher, this is not possible with galvanized and hot dip galvanized layers.

#2. Excellent heat resistance

Since the Dakoro-coated chromic acid polymer has no crystal water and the melting point of the aluminum/zinc sheet is high, the coating has excellent high-temperature corrosion resistance. The Dacromet coating has a heat resistance temperature of 300 ° C. It can be used continuously for a long time at 250 ° C. Its corrosion resistance is almost unaffected, and the passivation film on the surface of the electroplated zinc layer is destroyed at around 70 ° C, and the corrosion resistance is a sharp decline.
Zinc Flake Coating

#3. No hydrogen brittleness

During the technical treatment of Dacromet, there is no acid washing, electrodeposition, electric de-oiling, etc., and there is no electrochemical reaction of hydrogen evolution caused by the electro-galvanizing process, so the material will not cause hydrogen embrittlement. It is therefore particularly suitable for handling elastic parts and high-strength workpieces.

#4. The goodrecoatability​

The appearance of Dacromet coating is silver-gray with good adhesion to the substrate and various coatings. It can be used as a top layer or as a primer for various coatings. Electrochemical reactions occur between metals due to potential differences. For galvanized layers, both the iron-based and aluminum-based layers are electrochemically resistant and greatly reduce corrosion resistance. For Dacromet anti-corrosion layer, since the anti-corrosion is based on the chromic acid passivation and the controlled sacrificial protection of the scaly zinc layer, no electrochemical corrosion is generated, so the Zn consumption is relatively suppressed corrosion of Al is suppressed.

#5. Excellent permeability​

The Dacromet treatment fluid can penetrate into the tight joint of the workpiece to form a rust-proof coating. If the method of electroplating is used, the inner surface of the tubular member is hardly plated due to the shielding effect. However, because Dacromet treatment is applied by coating and has good permeability, it can be applied to improve the rust prevention ability inside and outside.
Dacromet coating

#6. No pollution​

When electroplating zinc, there is a problem of sewage discharge containing zinc, alkali, chromic acid, etc., which will cause large pollution. The temperature of hot dip zinc is high, and the released zinc vapor and HCL are harmful to human health. Most of the current heat zinc production must be carried out away from urban and rural areas. The Dacromet process has created a new field of metal corrosion protection. Because Dacromet treatment is a closed process, the substances that are volatilized during the baking process are mainly water, do not contain other harmful substances that are controlled, and have no pollution to the environment.
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