Chemical Conversion Coating and Chemical Oxidation
Chemical Conversion (Passivation) - is a coating that is produced by electrochemical or chemical reaction of metals, giving a superficial layer which contains the metal compound.
Passivation is the use of a light coat of a protective material, such as metal oxide, to create a shell against corrosion. It offers economical protection against corrosion and a surface suitable for painting. It also preserves electric conductivity, in contrast to anodizing which produces coatings that are non-conductive. Chromate and Cr-free conversion coating is a common way of passivating not only aluminum, but also zinc, cadmium, copper, silver, magnesium, and tin alloys.
Chemical Oxidation is one of the chemical conversion coatings. With the use of chemical substances when applied to the metal surfaces, this starts chemical reaction which creates oxidation on the metal's surface - a stable anti-rust oxide film. Commonly used in aluminum and aluminum alloy, copper and copper alloy, carbon steel and so on.
Aluminum and aluminum alloys are generally passivated with sodium carbonate solution of chromate (鉻酸鹽), silicate (矽酸鹽), phosphate (磷酸鹽); copper and copper alloy with caustic soda solution containing oxidant; while carbon steel is caustic soda solution with nitrate.
三價鉻
Chromate Passivation
鉻酸鹽皮膜處理 (三價鉻 Cr+3)
■ ROHS/WEEE compliant：YES
■ Benefits:
1. Cost is better than Cr+6, because the toxic is less
2. Improved corrosion resistance (withstands 72h+ salt/spray test)
3. Lower concentration levels result in less chromium waste
4. Painting adhesionability
無鉻鈍化/非鉻皮膜
Cr-free Passivation
無鉻鈍化/非鉻皮膜
■ ROHS/WEEE compliant：YES
■ Benefits:
1. Corrosion resistant
2. Painting adhesionability
六價鉻
Hexavalent Chromium (Cr+6)
六價鉻
■ ROHS/WEEE compliant：NO
■ Benefits:
1. Corrosion resistant
2. Painting adhesionability
磷酸鹽鈍化
Phosphate passivation
磷酸鹽鈍化
■ ROHS/WEEE compliant：YES
■ Benefits:
1. Corrosion resistant
2. Thickness 2～6μm, improves wear resistance of parts
2. Painting adhesionability
鏽鋼鈍化
Passivation of Stainless Steel & Copper Anti-Oxidization
不鏽鋼鈍化 & 銅製品鈍化皮膜處理
■ ROHS/WEEE compliant：YES
■ Benefits:
Improved stainless steel corrosion protection without plating
不鏽鋼黑化
Black Oxidation for Stainless Steel
不鏽鋼黑化
■ ROHS/WEEE compliant：YES
■ Benefits:
1. Corrosion resistant
2. Painting adhersionability
電解拋光
Electropolishing
電解拋光
■ ROHS/WEEE compliant：YES
■ Benefits:
Reduces or eliminates stressed and disturbed layers caused by heat treating, decarburization, microscopic scratches, tool marks, grinding checks, cutting and abrasive finishing, thus greatly improving fatigue life.
Plating Characteristics
*** For detailed selection list of Plating and Coating processes, please refer to Plating & Coating Table