Size-separated particle fractions of stainless steel welding fume particles – A multi-analytical characterization focusing on surface oxide speciation and release of hexavalent chromium

Abstract

Welding fume of stainless steels is potentially health hazardous. The aim of this study was to investigate the manganese (Mn) and chromium (Cr) speciation of welding fume particles and their extent of metal release relevant for an inhalation scenario, as a function of particle size, welding method (manual metal arc welding, metal arc welding using an active shielding gas), different electrodes (solid wires and flux-cored wires) and shielding gases, and base alloy (austenitic AISI 304L and duplex stainless steel LDX2101). Metal release investigations were performed in phosphate buffered saline (PBS), pH 7.3, 37°, 24h. The particles were characterized by means of microscopic, spectroscopic, and electroanalytical methods. Cr was predominantly released from particles of the welding fume when exposed in PBS [3-96% of the total amount of Cr, of which up to 70% as Cr(VI)], followed by Mn, nickel, and iron. Duplex stainless steel welded with a flux-cored wire generated a welding fume that released most Cr(VI). Nano-sized particles released a significantly higher amount of nickel compared with micron-sized particle fractions. The welding fume did not contain any solitary known chromate compounds, but multi-elemental highly oxidized oxide(s) (iron, Cr, and Mn, possibly bismuth and silicon).

High variability in toxicity of welding fume nanoparticles from stainless steel in lung cells and reporter cell lines: the role of particle reactivity and solubility

“…When considering the impact of the base alloy and filler alloy composition (which is selected based on the base alloy) comparing welding fumes generated with FCWs only, our results showed that the UNS S32101 alloy (F3-F4) generated fume particles released more Cr(VI) in PBS, compared to fume particles from 304 L welding under similar conditions (F1-F2). These findings are in accordance with results reported by Mei et al (2018). In line with this, the F3 particles were also more genotoxic compared to F1 (Figure 7).…”

“…The images predominantly show nano-sized primary particles typically sized 20-30 nm in aggregates/ agglomerates. Our previous published (Mei et al 2018) and unpublished SEM and TEM images show similar particle sizes for welding particles generated at various conditions.…”

“…Welders choose welding conditions, such as potential, current, arc mode, melting rate, filler material feed rate, and choice of shielding gas, based on, among others, the base material and its thickness. The vaporized material generated in the welding process oxidizes and results in a fume mainly containing agglomerates of nanometer-sized primary particles of metals and metal oxides (Mei et al 2018). The composition of the fume is largely dependent on whether a stainless steel or mild steel base alloy is welded.…”

“…Cr has been shown to exist as both Cr(III) and Cr(VI) in welding fume particles from stainless steel (Mei et al 2018). Cr(VI) is classified as a human carcinogen by IARC (2012) and has been shown to be more permeable through plasma membranes compared to other chemical forms of chromium.…”

“…There is no welding fume that is representative for all stainless steel grades, but its composition, such as the Cr(VI) concentration, and generation rate have been shown to vary widely when altering common welding processes and parameters (Zimmer and Biswas 2001;Yoon, Paik, and Kim 2003;Keane et al 2009;Antonini et al 2011). Mei et al (2018) further demonstrated an evident effect of the electrode type and conditions related to the base alloy (type of filler material and welding conditions) for the release of metals from the fume particles, in particular Cr(VI) in PBS. It is, however, unclear whether the release of Cr(VI) in PBS correlates with the observed toxicity in lung cells.…”