Specifing Anodizing for RoHS Compliance 1

[jgrav2]

We have some anodized parts that are currently being specified with "Type 2 class 2 (red)"

I understand that sulfuric anodizing has no RoHS issues, only the sealers. How should I specify the RoHS compliance?

Suggestions I already have are: "Type 2 class 2 (red) using non Cr(VI) processes." and "Type 2 class 2 (red) with Trivalant Cr sealer".

Any other suggestions?

 

[kenvlach]

Re 'Trivalant Cr sealer' for anodized aluminum.
I'm not aware of any such beast. The majority of anodize in the US is sealed using nickel acetate solutions, which operate at lower temperature and resist contaminants better than the nearly boiling DI water seal. The nickel is at very trace amounts in the anodize; most of the pore sealing is hydrated aluminum oxide. I've never heard of any allergic reaction as occurs with nickel-containing jewelry.

Dichromate sealing (hexavalent Cr) is mostly done for Type III, Class 1 parts requiring maximum corrosion resistance. It gives a yellowish hue to parts, so unpopular for dyed parts. However, you must specify non-hexavalent chromium sealing, as it is allowed in MIL-A-8625F (available at ASSIST:

http://assist.daps.dla.mil/quicksearch).

Your suggested "Type 2 class 2 (red) using non Cr(VI) processes" should suffice.

Dyestuffs. Most immersion anodize dyes contain chromium. E.g., Bourdeaux R (red) is described as an azo compound containing trivalent chromium. But, perhaps a trace of Cr⁺⁶?. So there is a disclaimer:

"Clariant's products are to be used by knowledgeable and/or sophisticated users. Clariant's product information, notices or instructions as to the handling, use, storage or disposal of any product, including its use alone or in combination with other products, or as to any apparatus or process for the use of any product, are based upon information believed to be reliable; notwithstanding, users must make their own determination that use of the product in the anticipated manner or application is appropriate. When Clariant products are incorporated into a purchaser's product, the purchaser must make its own determination as to what instructions and warranties to provide.
...
In no event shall Clariant be liable for loss of profits or any other indirect, remote or consequential losses or damages."

The above notwithstanding, I prefer Clariant's dyes. They do offer a number of heavy metal-free dyes (often denoted MF in product listings). The Blue A, Blue G, Gold 4N (contains iron) and Green AENX are commonly used. The MF blacks and reds need improvement.

You can find Clariant's 61 immersion dyes listed through a search at

http://pigments.clariant.com/pa/int...d00212d597eab922c1256fe900334aa3?OpenDocument

--- Pick 'Aluminum Anodizing' for Industry, 'Coloration' for Application, 'All' for Color, then Search.
Note: Sanodal dyes are those considered fade-resistant enough for outdoor use.

Another dyeing process, 'two step' or electrolytic dyeing, commonly uses fairly non-hazardous tin salts. Commonly used for architectural bronzes.

 

[kenvlach]

Another anodize dye supplier, U. S. Specialty Color, has an on-line color chart:

http://www.usspecialty.com/

The product listing shows that one Cr-free red dye is available: Deep Red L.

 

[jgrav2]

Thanks kenvlach,

I will keep this info in case my vendors have a question on where to get the non cr6 dyes. I changed my specs to say: "Type 2 Class 2 (red) using non cr6 processes and dyes" This should cover everything.

jgrav2