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MD Process High Corrosion Resistance Anodizing

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About MD (Miyaki Die Cast) Process

  • Pure aluminum = good corrosion resistance (good rust resistance)
  • Other aluminum alloys = poor corrosion resistance (bad rust resistance)

    Wrought materials, die cast parts, etc.

The introduction of additional elements during die casting significantly lowers corrosion resistance,necessitating surface treatment.

While there are other methods of enhancing corrosion resistance including surface treatments such as conversion treatment, plating, and anodizing treatment, the inevitable banning of hexavalent chromium due to environmental concerns leaves very few tried and tested surface treatments offering sufficient corrosion resistance.

So, we decided to reexamine the conventional anodizing treatment process…

  • To realize stable film generation on materials like aluminum difficult to coat with anodizing
  • To provide sufficient corrosion resistance

We developed the MD Process (Miyaki Die Cast Process).

Cross-sectional Photo of Film Formed with MD Process

Cross-sectional Photo of Film Formed with MD Process

MD Process Characteristics (image)

Die cast parts cannot be anodized like wrought materials as they contain numerous additional elements like copper, iron and silicon.
The ideal combination of electrolytic solution, concentration, temperature, and current for the anodizing treatment of die cast parts facilitates the formation of a good film structure with uniform film thickness and corrosion resistance.
The appropriate chemicals are also chosen for degreasing and sealing cast metal and die cast parts.

  • Standard Anodizing

    The anodizing film of standard die cast parts can’t form good cells. The presence of numerous melted sections prevents effective sealing, so there is no corrosion resistance.

    Standard Anodizing

  • MD Process

    Production of an even film as with wrought materials provides sufficient corrosion resistance for die cast parts.

    MD Process

Comparison of Corrosion Resistance with 500 hour Salt Spray Test

MD Process 5~10μm (ADC12)

Comparison of Corrosion Resistance with 500 hour Salt Spray Test

MD Process Properties Chart

Material Film Thickness (μm) Standard Hardness Film Characteristics Remarks
Recommended Limit (HV) Hardness Generation Capabilities Corrosion Resistance
AC2A・B 10 20 250 The material’s surface is rough, and surface cavities are visible after anodizing treatment.
AC4C 20 40 400 Good film forming properties and surface roughness compared to other minerals.
AC7A・B 20 40 400 Relatively good film compared to other minerals.
AC8A 20 40 400 Superb strength and wear resistance makes it the perfect material for engine pistons. (good anodizing properties)
ADC6 20 40 400 Good film generation compared with other die cast treatments.
ADC12 10 20 300 Effect of additional element hinders thick film. Silicon and release agent easily left behind, causing excessive color variations.
Material Film Thickness (μm)
Recommended Limit
AC2A・B 10 20
AC4C 20 40
AC7A・B 20 40
AC8A 20 40
ADC6 20 40
ADC12 10 20
Material Standard Hardness
(HV)
AC2A・B 250
AC4C 400
AC7A・B 400
AC8A 400
ADC6 400
ADC12 300
Material Film Characteristics
Hardness Generation Capabilities
AC2A・B
AC4C
AC7A・B
AC8A
ADC6
ADC12
Material Film Characteristics
Corrosion Resistance
AC2A・B
AC4C
AC7A・B
AC8A
ADC6
ADC12
Material Remarks
AC2A・B The material’s surface is rough, and surface cavities are visible after anodizing treatment.
AC4C Good film forming properties and surface roughness compared to other minerals.
AC7A・B Relatively good film compared to other minerals.
AC8A Superb strength and wear resistance makes it the perfect material for engine pistons. (good anodizing properties)
ADC6 Good film generation compared with other die cast treatments.
ADC12 Effect of additional element hinders thick film. Silicon and release agent easily left behind, causing excessive color variations.

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