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Zinc Plating

Zinc plating is the process of covering substrate metals (like carbon steel and alloy steel, etc.) with a layer of zinc to protect the substrate from corrosion. It is usually used to protect and improve the appearance of ferrous metals, as a corrosion barrier. Our Zinc Plating is basically according to ASTM B-633 ELECTRODEPOSITED COATINGS OF ZINC ON IRON AND STEEL.

 

Class

 Demand        Service Condition      Minimal thickness in microns          

 Fe/Zn25         SC4 (very severe)       25 micron (0.0010")           

II 

 Fe/Zn12  SC3 (severe)  12 micron (0.0005")

III

 Fe/Zn8  SC2 (moderate)      8 micron (0.0003")

     IV     

 Fe/Zn5  SC1 (mild)  5 micron (0.0002")

 

 

ASTM Type

 

Type Description Corrosion Resistance
according to ASTM B117 
Remarks
Type I  Zinc coating with no additional treatment  N/A  Usually not applicable
Type II  Zinc coating with colorful chromate passivation  96 hours
 48 hours
 160 hours
 Yellow-iridescent
 Black
 Olive Green
Type III  Zinc coating with colorless chromate passivation  12 hours  Colorless to blue
Type IV  Zinc coating with phosphate passivation  N/A  N/A in green coat
Type V   Zinc coating with colorless RoHS compliance passivation   72 hours  Colorless to blue
  Type VI    Zinc coating with colorful RoHS compliance passivation  120 hours  Yellow-iridescent
 Black

 

Anodizing

The most common acids used for aluminum anodizing are sulfuric or chromic. U.S. Mil-A-8625 is also the most commonly referenced specification, and describes 3 general types of anodizing:

 

 

ASTM Type  Class Thickness
 Type I 

 Chromic Acid Anodizing

 0.5 - 7.6 um

 

 Type II 

 Conventional Sulfuric Acid Anodizing  

 Class 1: A non-dyed anodizing process.

 Class 2: A dyed anodizing process in which you can obtain a large variety of colors.

 

 5.0 - 12.7 um

 5.0 - 25.4 um

 

     Type III     

 Hard Coat Anodizing

 Class 1: A non-dyed anodizing process.

 Class 2: A dyed anodizing process in which black is used.

 

 25.4 - 115.0 um 

 

Alodine / Chemical Conversion

Alodine, so called chromatic passivation or chemical film for aluminum is a chemical conversion process under the MIL-DTL-5541 specification. These coating processes are categorized by the following types, classes and colors.

 

Types Description   RoHS Compliance  
 Type I 

 Compositions containing hexavalent chromium.

 Color: Clear or Yellow

 No

Type II

 Compositions containing no hexavalent chromium.

 Color: Clear or Yellow

 Yes

Classes Description  
  Class 1A  

 For maximum protection against corrosion, painted or unpainted.

 

Class 3

 For protection against corrosion where low electrical resistance is required.