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Trivalent vs Hexavalent passivation

1 How much is the salt spray life of trivalant passivation with 7-12 micron Zn coating?
2 What is the approx.cost diffrence of hexavalant and trivalant passivation?
3 How can we identify the trivalant or haxavalant passivation?

Pawan Kumar
Engineer - Punjab, India
May 1, 2008

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May 11, 2008

Mr Pawan Kumar

1) You did not state the COLOR of TVC required. Here is a short list

Blue Bright TVC. 96 to 120 Hours to WHITE rust.
Green to yellow NON DYE TVC used at Room Temp. 120 to 240 Hours depending on strength of solution and time of immersion.
Black TVC. 96 to 168 Hours .

ALL the timings are stated to WHITE RUST.

2) Cost.

Compared to Hex Chrome , the cost increase will depend on which Trivalent chromate you choose.

Blue Bright to 120 Hrs. Cost diff is up to 2.5 times.
Blue Bright to 24 Hrs is cheaper than HEX chromate. !

Yellow to Gren shades at Room temp. Works out 1.25 times over Hex Chrome BUT the life is greater so you get more as well.

3) There is a Spot Test known as the DIPHENYL CARBAZIDE spot test. ( Some places in Europe ban this test)

It is available on the net. The ready to use solution is available as a kit to mix and consume within 6 days of mixing, and stored in a cool atmosphere.

Good luck.

Asif Nurie [deceased]
- New Delhi, India
With deep regret we sadly advise that Asif passed away on Jan 24, 2016