Letter 39839

Alodine Color without Chromium  

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We are looking for an Alodine replacement that is not clear. So far this is all we have found. We are doing Alodine primarily on Aluminum. We like the golden color we get right now. We use it as an identifier that the Alodine has been done as well. Are there any other colors which can be produced from an Alodine replacement with no hexavalent?

Ken Pokigo
electronics - Angola, New York

Hi, Ken. Adding yellow dye can be done with some of the thicker types of hex-free conversion coatings -- but the Mil-C-5541 [link is to spec at TechStreet] approved TCP processes cannot be dyed (the film is too thin); attempts to dye it have all reduced the corrosion resistance.

The characteristic golden color of hexavalent chromium is not a dye; it is the natural color of the toxin, and it's what allows us to instantly recognize that handling the object will release carcinogenic hexavalent chromium.

So this blowhard (me) gets to say it again: Why try to make parts look like they are toxic, carcinogenic, and forbidden by the EU, and possibly face targeting by public interest groups, even though you have invested the time, effort and extra cost to make sure they are actually safe and "green"?

It seems at least possible to me that the EU may decide that testing for hex chrome is so burdensome and expensive for inexpensive fasteners that they may address this via the timesaver of applying the simple preliminary filter that "if it's golden color it must be rejected"

Ted Mooney, P.E.  finishing.com Brick, New Jersey

The non-chromium replacements for MIL-C-5541 chromate conversion coatings I have seen are all clear. A very legitimate question is how does one assure the quality or even the existance of a coating one cannot visually inspect. Historically, the "golden" color is the only quick indication of a quality conversion coating on aluminum. Are there non-chromium replacement products that can be inspected visually or are there other simple quality tests available?

Chris Jurey Luke Engineering & Mfg. Co. Inc. Wadsworth, OH

I've come across a few that have an inherent color (other than gold) - I don't remember which though. And I know that most can be dyed. But, what Ted says makes sense - if you are going to dye it, why dye it to match an older process that is on the way to being fazed out? Why not blue, or green, or anything other than gold?

Jim Gorsich Accurate Anodizing Inc. Compton, CA, USA

The answer to the question of why you would want a RoHS gold Alodine replacement with the same coloration is simple, because your customers like it!

Also, if it turns out to be so simple for the EU to identify and "reject" parts fot the presence of chromiun by, "it looks gold", then so be it. I'll be glad to accept all the gold plated parts they can filter out for me!

Ken Pokigo, again
electronics - Angola, New York

Gold chromate will never be mistaken for gold, Ken :-)

'Product stewardship' was a crucial part of 'mission statement' last decade, But management themes come and go, and I guess responsibility isn't particularly "in" so far this decade. But leadership is always in, and if ever there was a right time for we in the industry to work to get our customers to understand and to think fresh instead of dyeing non-toxic finishes the inherent, characteristic color of the toxin, now would be the time.

The new "TCP / I can't see" replacement technology is colorless and very thin and my understanding is that attempts to dye it yellow or black so far have significantly reduced the corrosion resistance. Pastels are pastel because they lack saturation, so they may be more doable with these very thin coatings. If pastel pink or pale violet or light spring green were a quick and reliable indicator of the presence of a toxin-free TCP coating, we'd have the win-win situation we need :-)

Ted Mooney finishing.com Brick, New Jersey

We have been using TCP for a year now. I can tell you that it is not entirely colorless, but you won't a good gold out of it. When properly applied, TCP should have a very, very, very light tinge of brown. You have to know what your looking for. As to the dye, I've had numerous discussions with the folks at NAVAIR. The problem with dye is that it contaminates the bath to the point that salt spray failure occurs. NAVAIR has been working on this aspect for a few years but to no avail.

Justin Crisp
- Indianapolis, Indiana

In line with what Ted said - While the customer is always right, that doesn't mean that they are always educated or unwilling to be persuaded. Dyeing the parts yellow is just silly - silly from an environmental perspective in that it makes them much harder to tell apart from hex-chrome containing parts when it comes to recyclying and such and silly from a business perspective with it making it impossible to brag about how "my parts are better for the environment - just look at the color! (rather than that old toxic yellow)"

Yeah - the customer may want gold colored parts right now; that is no reason why we shouldn't be encouraging them to change.

Jim Gorsich Accurate Anodizing Inc. Compton, CA, USA

We currently have many parts that have the gold color. I believe a clear is acceptable if we have the ability to verify the plating at the incoming inspection.
Are there any platers out there that have tried to add a flourescent to the process so the parts can be verified under a black light source? This is common use on PC boards to verify the application of clear conformal coat. I do understand this is more of a painting process. thanks

J Dallas Parr
- Santa Rosa, California

Trivalent Tester LLC has recently developed a drop test kit to enable verification of the presence of TYPE II Trivalent Chromium Conversion Coating on an aluminum substrate.

Jim Savoy
Sr Quality Engineer - Columbia, Maryland