finishing.com logo
    HOME / sitemapFAQsBOOKSHelp WantedsAdvertiseContact   you are here: Hotline/Forum => Letter 34491
most fun in metal finishing

ASTM B-633 and Hexavalent Chromium

+++++

I need to specify platings that do not contain Hexavalent Chromium for parts that will be used in the automotive industry. Do I need to specifically call out the use of Trivalent Chromium, or is it covered in the specifications used for ASTM B633 [link is to spec at TechStreet] ?

1 Do all ASTM B633 Type II platings use Hexavalent Chromium?

2 Can you get a type II finish that uses Trivalent?

3 Do all ASTM B633 Type III platings NOT use Hexavalent Chromium?

I have not heard much about the Type IV finishes. Do they use Hex or Trivalent chromium, are they available in colours, and do they protect as well as the type II or III finishes?

If anyone knows of a good plating guide to pick up, please let me know.

Claudio Zubin
Auto Parts - Winnipeg, MB, Canada


+++++

I have the exact same questions. Did you ever get the answers you were looking for? Does anybody know this info?

Doug Kovacs
- North Canton, Ohio


+++++

Hello Claudio and Doug,

My complements for an excellent round of questions!

In response to your questions re ASTM B 633; I have an old version of the spec so my opinions are based upon the one I have.

1 Do all ASTM B633 Type II platings use Hexavalent Chromium?
Ans: The answer is Yes. ASTM B 633 and all other worldwide standards were written around the time when no one spoke about trivalent. It definitely implies Hex Chrome.

2 Can you get a type II finish that uses Trivalent?
Ans: Trivalent chromates give paler and lighter finishes; some use metals, some use permanganates, some use dyes, in order to replicate the Hex finish. You can get the same finish only for blue and black hex chrome with tri substitutes, but not for yellow or olive as of yet. A Blue with pale yellow is the best replacement for yellow as of now.

3 Do all ASTM B633 Type III platings NOT use Hexavalent Chromium?
Ans: No it does not imply that. Type III (colorless)generally refers to Hex Chrome that has been bleached off to give a clear look. It still will have Hex Chrome.

I have not heard much about the Type IV finishes. Do they use Hex or Trivalent chromium, are they available in colours, and do they protect as well as the type II or III finishes?
Ans: In 24 years I have only been asked this question once before and I presume it involves phosphating over zinc plating for those heavy phosphating grammage applications, where normal phosphating will not provide enough zinc phosphate that is required in the deposit. No, other colors may not be available if my presumption is right.

khozema Khozema Vahanwala
Saify Ind
 
Bangalore, Karnataka, India


+++++

As far as I remember the RoHS Directive asks for no more than 1000 ppm (0.01%) of hex Cr of an homogeneous item.

To calculate it is very difficult, as the plating is a few molecules thick. According to RoHS the homogeneous and non-homogeneous are defined in such manner that every one may understand that the layer is removable (let see how).

In my opinion a Mil-C-5541 [link is to spec at TechStreet] plating withstands the 1000 ppm that means that the plating passes the barrier (at least on aluminium plates).
What do you say?

Dan Yariv-Weisbuch
- Oranit, Israel

ADD a Q or A to THIS thread START a NEW THREADView This Week's HOT TOPICS

disclaim

 seek

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & DevicesUsed & Surplus


©1995-2014 finishing.com     -    Privacy    -    Search