Foshan Dechenghezhong Chemistry co.,LTD
No,12 Yuyang 2nd Road, Huchong Industrial District, Nanzhuang Town,
Chancheng District, Foshan City, Guangdong, China
Tel:0086-757-82012410
Fax:0086-757-82012430
Website:http://dchz.en.alibaba.com
E-mail:fsdchz@outlook.com
DCHZ-Trivalent Chromate Yellow Passivant
High Corrosion and QUV Resistant Trivalent Iridescent Yellow Bright Chromate
DCHZ-Yellow is a single dip yellow trivalent chromate that offers high salt spray resistance of up to 150
hours to white rust per ASTM B-117 (zinc plating thickness 0.3 mil) and QUV resistance at 1000 hours
on Q-Panel. No additional top coat is required to obtain this high degree of corrosion resistance.
It produces a beautiful yellow bright trivalent chromate to meet automotive and all other industrial
standards. Hours to red rust depend upon the thickness of the zinc plate. One additional benefit is this
trivalent yellow chromate can be baked, increasing the corrosion resistance up to 300 hours and without
fading of color. Passes the ISO 3613:2000(E) section 5.9 adhesion by abrasion test and the ISO
3613:2000 (E) section 5.6 for a negative result on hexavalent chromate after salt spray testing. What this
means is that after salt spraying the part, the trivalent chrome does not convert to hexavalent chrome
using this salt spray test ASTM B-117. (All tests performed on Qpanels)
It produces a true yellow conversion coating on plated alkaline non-cyanide, cyanide and chloride zinc
deposits. Note salt spray hours less on cyanide zinc.
Baking the parts at 350-400ºF for 4-24 hours results in the highest corrosion protection.
This will offer the metal finisher significant cost savings because it eliminates the costs of having to
chromate after baking.
It is simple to control by pH, temperature, and the ratio of 1 parts DCHZ-Yellow A and 1.4 parts of
DCHZ-Yellow B added separately, but at the same time. (DO NOT MIX DCHZ-Yellow A AND
DCHZ-Yellow B)
DCHZ-Yellow A as the base trivalent chromate and DCHZ-Yellow B for color and corrosion protection
and both have to be added together.
DO NOT MIX! DO NOT ONLY ADD DCHZ-Yellow B!
Solution Make-Up and Operating Parameters
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Range
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Optimum
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DCHZ-Yellow A
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5.0 - 7.5% by volume
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7.5% by volume
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DCHZ-Yellow B
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2.5-7.5% by volume
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5.0% by volume
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Raise pH to 1.8 at make up
with Ammonium Hydroxide.
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Temperature
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90-150ºF (32-66ºC)
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120ºF (54ºC)
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pH (*)
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1.65 – 2.0
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1.8
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Time
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30 seconds-5 minutes
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1 minute
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|
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Range
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Optimum
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Agitation
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Air agitation
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High volume, low pressure,
do not use compressed air
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* Lower pH with 10% nitric acid solution. Do not lower the pH less than 1.65.
Raise pH with Ammonium Hydroxide.
* The pH will need to be raised to 1.8 after make up of a new bath, approximately 1.5
liters of ammonium hydroxide per 100 gallons working solution.
* Use pH meter calibrated with 1.68 buffer.
|
Color
Yellower shade: 70 - 105º F (Lowering temperature below optimum can affect
corrosion resistance.)
Greener shade: 105 - 140º F
Processing Procedure
1. Zinc plated surfaces. The brightness of the final finish will be directly related to the brightness of the
plated surfaces.
2. Cold water rinse.
3. 0.5-1.0 % by volume Sulfuric Acid rinse to neutralize residual plating solution.
4. Cold water rinse.
5. Immersion in DCHZ-Yellow solution for the length of time required to produce the desired finish.
6. Cold water rinse.
7. Hot Air Dry – 150ºF, or Spin Dry
8. BAKE parts for highest corrosion resistance at 350-400ºF for 4-24 hours.
Caution
DCHZ-Yellow A contains nitric acid. The Material Safety Data Sheets for DCHZ-Yellow A and DCHZ-Yellow B must be read and understood before working with these products.
Equipment Requirements
Tanks: 304 or 316 stainless steel, Koroseal lined steel, polyethylene or PVC. Hooks, racks and baskets
require the same materials. The working solution should be exhausted.
Heaters: If needed, should be 304 or 316 stainless steel.
