Category: Hexavalent Chromium Hazards
Environment, Health & Safety
The valency states of chromium, including trivalent and hexavalent chromium are outlined. The valency, (oxidation state), of chromium, as an alloying constituent of stainless steels, is 0, (zero). The chromium in solid stainless steels should not be regarded as a health hazard, but care should be taken with the fumes from welding stainless steels.
The European ‘ELV’ directive 2000/53/EC should not have a detrimental affect on stainless steels intended for applications in automobiles. Analysis work done so far shows that the levels of lead, mercury and cadmium are well below the levels currently understood to be the limits. Stainless steels do not contain hexavalent chromium and so this requirement is not relevant.
Both flux- and gas-shielded processes for welding stainless steels generate fume. So does plasma arc cutting. Fume consists of both particles and gases, including ozone. Concerns that fume, particularly particles containing hexavalent chromium, is a cause of cancer have not been supported by extensive studies, although there is a slight excess of lung cancers among all welders. Therefore it is sensible to limit contact with welding fume and there are statutory requirements.
The original version of European directive 2002/95/EC effectively out-lawed stainless steels and many other materials as no lead, mercury, cadmium, hexavalent chromium, poly-brominated biphenyls, (PBB), or polybrominated diphenyl ethers, (PBDE), content was to be allowed in materials that would be part of equipment ‘which is dependant on electric current in order to work properly’. This has now been rectified in the Official Journal of the European Union document C(2005) 3143, 2005/618/EC, published on 18th August 2005, allows maximum levels of 0.1% for all these, except cadmium which is 0.01%, which is the same as in the ELV directive. In stainless steels only the restrictions to the elements lead, mercury and cadmium are relevant. Commercially produced stainless steels can be expected to comply with the amended RoHS requirements, without actual values being measured or declared by the steelmaker or supplier.
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