Trivalent Chromates FAQ

1) What are chromates?

Chromates are used in order to coat metal parts to provide a longer life for the part. It is commonly used on zinc-plated parts in order to provide protection from corrosion such as white rust or red rust. Chromates can come in many different color variations: clear, blue, yellow, or black. EPI offers both hexavalent chromate and trivalent chromates in blue and yellow variations.

2) What Makes EPI’s trivalent chromate processes superior?

Other chromate processes often require multiple dips in order to achieve the desired results. With EPI’s chromates, you no longer need multiple dips to achieve both a bright chromate finish and high salt spray resistance. EPI’s trivalent chromates are also RoHS compliant and environmentally friendly.

3) What chromate solutions does EPI offer?

EPI provides both trivalent chromates in blue and yellow finishes to meet the standards of current European Union initiatives and RoHS standards, but also provides hexavalent chromates for metal finishers to use on aluminum, zinc and cadmium.

4) What is the difference between trivalent chromates and hexavalent chromates?

Hexavalent chromates were once the most commonly used chromate throughout various industries. Today metal finishing processes are moving towards trivalent chromates to meet European Union initiatives End of Life of Vehicle (ELV) and RoHS. The usage of hexavalent chromates has been limited, resulting in trivalent chromates now being used more predominantly. Trivalent chromates produce a harder, scratch-resistant coating with lower water content providing more heat resistance. EPI’s trivalent chromates address some of the major issues when switching over from hexavalent chromates:

• Color Variability
  
  EPI offers both an Ultra Blue and an Ultra Yellow chromate. Both produce a true conversion coating on plated alkaline non-cyanide and chloride zinc deposits.

• Corrosion Resistance
  
  Most metal finishers are worried of getting poor results when transitioning to trivalent chromates fearing a lower corrosion resistance. However, both the E-Chrome Ultra Blue and E-Chrome Ultra Yellow trivalent chromates offer high salt spray resistance on zinc-plated surfaces of up to 150 hours on white rust, per ASTM B-117. Resistance to red rust is typically 240 hours, depending on zinc plate thickness. No additional top coat is needed to obtain this high degree of corrosion resistance.

• Easy to Control – Utilizes Only a Single Dip
  
  Ultra Blue and Ultra Yellow trivalent chromates can be used with automatic feeder equipment, which boosts productivity.

5) What benefits can I expect from EPI’s E-Chrome trivalent chromates?

E-Chrome Ultra Blue Trivalent Chromate:

• Blue Bright trivalent chromate
• Non-yellowing
• High corrosion resistance
• Single dip
• Easy to control – operator friendly
• Stable bath with long life
• Utilize for both rack and barrel chromating
• Can be used with automatic feeder equipment
• Works well on plated zinc, die cast zinc and galvanized zinc surface

E-Chrome Ultra Yellow Trivalent Chromate:

• Bright yellow trivalent chromates
• High corrosion resistance up to 150 hours bake it up to 300 hours
• Bakeable – without fading
• Single dip
• Passes the thumb test does not wipe off easily
• Offers some UV resistance to the sun
• Easy to control – operator friendly
• Stable bath with long life
• Utilize for both rack and barrel chromating
• Can be used with automatic feeder equipment

6) What is the application process for trivalent chromate?

• Zinc plated surfaces. The brightness of the final finish will be directly related to the brightness of the plated surfaces.
• Cold water rinse
• 1% by volume Sulfuric Acid for E-Chrome Ultra Yellow or Nitric Acid rinse to neutralize residual plating solution
• Cold water rinse
• Immersion in trivalent chromate solution for the length of time required to produce the desired finish.
• Cold water rinse
• Hot Air Dry – 150° F or higher

7) Who uses hexavalent chromates and trivalent chromates?

Large companies such as lock manufactures or auto manufacturers use chromate on a large scale basis to strengthen metal parts. Below are some of the major industries that utilize both trivalent chromates and hexavalent chromates.

• Ammunition Manufacturers
• Appliance Industry
• Architectural Industry
• Auto Industry
• Collars/Coupling Industry
• Fastener Industry
• Hardware Industry
• Metal Stampers
• Military Components
• Power Hand Tool Manufacturer
• Recreational Vehicle Industry
• Tool & Die Industry

8) How can I purchase EPI chromate finishes?

To order EPI chromate finishes call 1-262-786-9330. You can also use our online request form for a free quote or sample parts finishing.