Ultrafine particles emitted by thermal spraying of metals

Thermal spraying (TS) is a surface treatment process, which enables different types of material (metals, metal alloys, ceramics and even plastics) to be deposited on various substrates. The coating product, in wire or powder form, is melted by a heat source and then sprayed onto a surface previously prepared by sandblasting.
Bémer et al. (2013) have shown that one specific thermal spraying process (electric arc) was particularly high emissive of ultrafine particles (UFP). In this study, emissions characterisation of TS was extended to the five main TS processes (wire flame, electric arc, powder flame, plasma and High Velocity Oxy-Fuel), and for two different metallic (or alloys) coating materials for each process.
Measurements confirm a significant exposure to UFP with an average of 90% of emitted particles in number classified as UFP, whatever the TS process or the sprayed material tested. The mean number concentration reached is especially high (close to 1014 particles/s).
All the results, added with the recent studies on nanotoxicology, support the fact that safety of the workers and particle rejections into atmosphere must be considered carefully regarding to TS activities