Chromium in Fume

Chromium can be present in fume in different forms. There are two main forms of chromium found in welding, trivalent, Cr3+, and hexavalent, Cr6+. Hexavalent chromium is considered the more hazardous of the two forms, and in welding fume it is a suspected human carcinogen.

Chromium is an element present in the consumables and parent material of stainless steels, heat-resisting steels, some creep-resisting steels, some high nickel alloys, and armour plate. It may also be present in some consumables used for hardfacing.

Chromium is also used as a coating for other materials, such as chrome plating, to give corrosion protection to steel, or to give a pleasing aesthetic appearance.

Chromium, as chromate, may also be found as a constituent of some industrial paints.

Welding or cutting materials containing chromium is likely to give chromium compounds in any particulate fume that is generated by the process. Whether it presents a significant hazard to health depends on the concentration and the duration of exposure.

Chromium Formation in Welding

When arc welding takes place on materials containing chromium, or by using consumables containing chromium, some of the chromium will be volatilised and escape from the protective gases in and around the arc. This metal vapour will be oxidised by the atmosphere to give particulate fume.

Depending on the specific welding process being used chromium can be present in the fume in several different valency states, including trivalent, Cr3+; and hexavalent, Cr6.

Effects of Exposure

The major toxic effects of chromium in industry are concentrated on the nose, the skin and the lungs.

The nose or, more specifically, the mucous membranes of the nasal septum, together with the skin of the hands and forearm, are the areas targeted by chromic acid and its salts.

Control Measures

When welding stainless steels using the MMA process there is a higher level of particulate fume generated than with MIG welding. However, an analysis of the fume generated would show that the MIG fume has a higher percentage of chromium present, typically 10 to 14%, this can be compared to about 6 to 8% for MMA.