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topic 2521

How bad is Chromate?


(1999)

Is there any Federal or State regulation actually ban the use of chromate in metal finishing? or is there regulations that render the use of chromate very expensive? If so, does someone know how much more expensive it is to use chromate as a result of the tightened regulation?

Choung Lai
- Philadelphia, Pennsylvania


(1999)

Mr. Lai,

Our company has not run into any regulations which ban hexavalent chromium based conversion coatings. Additonal expense due to regulations is not an issue either.

Richard Painter
- Cleveland, Ohio


(1999)

I don't know of any such ban in the U. S. and doubt that there will be one unless we run out of places to put chromium-containing sludge, or until replacement technologies exist, where we might not need chromates any more. The regulations which make chromates expensive are those which deal with the disposal of spent chromate solutions.

After seeing the progress (or lack of progress) after my thirty years in industry, I don't believe it will happen for quite some time. Most chromate usage in aluminum finishing is in the aerospace and military areas. I can speak mostly for aluminum finishers, and will let others comment on plating processes. My company, our major competitors, and even our large customers, such as the Boeing Co., have been working for many years on replacing chromates in aluminum finishing lines. (I have a job here at Henkel because of the company's commitment to replace chromium in aluminum finishing.) Let's look at chromate usage in aluminum finishing.

Chromates have been used as inhibitors in alkaline cleaners for aluminum, but other chemistries exist for that purpose, and not too many cleaners with chromates are used any more. Chromates in deoxidizers constitute the largest volume of chromates used in aluminum finishing, primarily in the aerospace industry, because of the nature of the alloys being processed. Chromated deoxidizers are hardly ever used in other aluminum finishing market areas. Several companies have been working for at least thirty years on non-chrome deoxidizers for aerospace alloys, but results have been mixed. Iron-based deoxidizers have been around for most of those thirty years but ferric iron just doesn't have the chemistry to replace chromates for applications requiring consistently passing salt spray tests. We have a few non-chrome, non-iron deoxidizers that are very close to being commercialized, and expect to make strides in the next several years.

Chromates for conversion coating are not as much a problem, in terms of handling chromates, as deoxidizers, because the chromate content is much less, and solution life is usually much longer. Regardless, several companies are looking for replacements. In terms of prepaint treatments, non-chrome conversion coatings have been around for about twenty years, and our latest generation of non-chrome products are superior in some ways to the traditional chrome-phosphate technology. The problem area for replacing chromate conversion coatings is for non-painted parts when bare salt spray requirements of military and aerospace specifications are involved. Again, our company is very close to meeting those requirements, but it will take a long time to commercialize and prove long-term any new technology. Some new technologies appear expensive until one factors in waste treatment costs for spent chromate solutions.

One success, you can find in other letters/discussions at this web site, has been the boric-sulfuric anodizing process, but again it will probably be a long time until it totally replaces chromic acid anodizing, if ever. The BSA process has been around for some 9 years, but some people are just now learning about it.

phil johnson

Phil Johnson
- Madison Heights, Michigan



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