Cadmium dichromate toxicity/safetyMay 18, 2012
Q. Hi, I'm going to be using some aircraft bolts in a project in which they will be handled often, and by kids. The coating on the bolts is a gold (and slightly green and pink) color which I believe is a cadmium dichromate coating. I'm concerned about possible cumulative toxicity from handling these parts, especially with kids. The information I've been able to find suggests that cadmium is very dangerous to inhale or ingest but generally safe to handle so long as handling doesn't lead to ingestion. But it seems that may be moot since the dichromate coating goes on over the cadmium. I haven't been able to find information about what type of dichromate is used to create the gold coating (potassium? sodium?). Inhaling or ingesting chrome is highly toxic, but I haven't found information about handling it. Since so many things are chrome plated, I would guess it's fairly safe, but I would like some expert advice on this because I don't want to expose kids to unnecessary danger. Thank you.Paul R
educator - Ridgewood, New York, USA
A. Hi Paul,
Cadmium and dichromates have long since been banned in the UK for use on anything other than safety critical applications. It surprises me that the USA doesn't have the same restrictions.
Anyway, dichromates, whether sodium or potassium or any other one has a whole list of toxic and environmental effects. Classified as a carcinogen and mutagen when inhaled, it is toxic in its own right. Hexavalent chromium compounds are also known to be sensitising both by inhalation and in contact with skin. Dichromates are also environmental toxins, being very toxic to the aquatic environment.
Personally I wouldn't buy these bolts at all for your particular application. Go for zinc plated, trivalent chrome passivated and clear coat varnish sealed. If you already have the bolts send them to a local reputable treatment house and have them stripped and re-plated with zinc, trivalent chrome passivated and clear coat varnished.
aerospace - Yeovil, Somerset, United Kingdom
A. I agree with Brian - avoid using them. Such coatings are generally prohibited in Europe, with the main exceptions being in aerospace and some defence industry applications
R&D practical scientist
The Pheasantries - Chesham, U.K.
A. Thanks Brian and Trevor. I was under the impression that the ban was based on the danger to workers during the coating process, rather than the danger of handling the finished product. Nonetheless, I'd rather not take any chances. Unfortunately these are the only type of bolts available for my application. I've coated them with an appliance epoxy, so that the chromate will not make contact with skin. The epoxy is tough and durable; and it's black, so if it were to wear away, that fact would be visible.Paul R
- Ridgewood, New York, USA