High Tech Dacromet Coating Standard Chemically Combined With Flake Zn

High Tech Dacromet Coating Standard Chemically Combined With Flake Zn

• Zinc flake coatings containing Cr(VI) (hexavalent chromium): surfaces containing Cr(VI) provide greater anti-corrosion protection with a thinner coating, but Cr(VI) is carcinogenic and poses a potential risk to the environment. New European decrees prohibit the use of surfaces containing Cr(VI). These include the Vehicle End-of-Life Directive EC 2000/53 as of 1 July 2007 and directive EC 2002/95 on electrical and electronic equipment (the RoHS Directive). For applications outside of the automotive and electrical industries these coatings are still valid.
• Solvent-based Cr(VI)-free zinc flake coatings.
• Water-based Cr(VI)-free zinc flake coatings.

Metal Dacromet Coating Introduction

Dacromet process is the most representative of today''s international metal surface treatment of high-tech, widely used in the world''s industrialized countries. Based on the author''s first-hand information in design and production, this paper describes in detail the characteristics of Dacromet coating process, the choice of equipment and Dacromet liquid, and the application of Dacromet coating process in China.

Composition/information on ingredients

MX6380 is made up of three packs: A,B and C;

Pack A: It is silver gray slurry that mainly chemically combined with super fine flake Zn, super fine flake Al and ethylene glycol. The radius-thickness ratio of Zn plate is 60~100.

Pack B: It is the solvent of the coating colored in orange-red and in water solution, which contain the Cr6+.

Pack C: It is the tackifier of the coating which mainly made up of cellulose white or yellowish powder.

Coating Process

3.1 Mix Ratio

Pack A:16.0 kg

Pack B:24.0 kg (the quantity can be increased appropriately if spray coating)

Pack C:0-50 g (according to different viscosity demand )

3.2

3.2.3

Stir the mixture about 1~2 hours fast after B added, then add C. C should be powdered if lump exist.(The barrel temperature should not be lower than 30℃, otherwise C will not be dissolved sufficiently .)Then stir 12 hours continuously.

3.2.4

The coating should be filtrated by 80~100 mesh stainless steel screen before pouring into dip barrel.

3.2.5

Temperature control device should be equipped with dip barrel to keep the temperature of coating at 22±2℃.(If temp. is too high, the paint is liable to deteriorate, and viscosity will be effected.) The coating should be stirred circularly to keep evenly dispersed.

3.2.6

Test density,PH,Temperature,Viscosity and Cr6+ content of coating every 8 hours if operate continuously.

4. Technical data

5. Mix Diagram

Caution: Temperature should be controlled in above operation.

6. Coating Process

6.1 Degreasing

The workpiece should be degreased if there is oil on the surface. There are three processing methods:

1.High temperature

2.Neutral water-base degreasing agent

3.Organic solvent such as methylene chloride.

6.2 Derusting

The workpiece can not be coated if there is rust or burr on the surface.The best processing method is shot blasting. The corrosion resistance of coating will be effected if acid cleaning adopted.

6.3 Coating

The workpiece afer degreasing and shot blasting should be coated through Dip-Spin coating or Spraying Coating.

6.4 Pre-heating

The workpiece after coated should be Pre-heated as soon as possible at 80~150℃ for 8~15 mins to evaporate. ( according to heat absorption of workpiece.)

6.5 Curing

The workpiece after pre-heating should be cured at 300-340℃ for 20-40 mins. ( according to heat absorption of workpiece.)

7. Attentions

Other chemicals such as any kinds of acid, alkali salt can not be mixed into coating, for these can activate Zn & Al plate to aging the coating.

Avoid irradiation of sunshine and ultraviolet ray for long time when operating, otherwise it will accelerate aging or polymerization of the coating .

It is very important to control the temperature of coating. If the temperature of coating changes when operating, it will effect the viscosity, then effec the coating quatity on workpiece. So the relations among temperature,viscosity and spinning process shoud be controlled well when coating.

The viscosity will be different if coating method is different. Choose low data if spray coating,and choose high data if dip spin coating.

8. Packing

9. Quality guarantee period

Before compound 6 months at 20℃

After compound 40 days at 20℃ ( It can be recycled if adding fresh coating continuously. )

It should be stored under 20℃ if not in use.