Controlling exposure to hexavalent chromium in welding fume

Abstract

Classified as an Occupational Hazard, welding fumes pose a threat due to the presence of Cr(VI), a known carcinogen. To effectively address this issue, it's crucial to comprehend the elemental form and mechanism of Cr(VI) formation in welding fumes. In this research, the formation of Cr(VI) in welding fumes was studied to understand the potential health hazards it poses to welders. FTIR was utilized to identify Cr(VI) species by analysing the vibrational peaks of various bonds in the compounds. FTIR proved useful in identifying Cr(VI) compounds by detecting the anti-symmetric vibrations of Cr-O-Cr, the symmetric stretching of CrO4 tetrahedra, and the stretching vibrations of the planar CrO3 structure of chromium trioxide. However, the study in quantifying the amount of Cr(VI) in welding fumes using FTIR and electrochemistry required further refinement and will be part of ongoing research.
As part of another study, in order to understand the mechanism of Cr(VI) formation in welding fumes using shielding gases, the composition of Cr(VI) in welding fumes was found to depend on the type of shielding gas used. The oxidation index of the shielding gas played a crucial role, with the lowest levels of Cr(VI) observed when using argon. Other important factors included the arc stability and ionization potential of the shielding gas. The combination of CO2 and O2 was found to provide the most stable arc and the lowest levels of Cr(VI), despite having the highest oxygen index. It was also observed that fluxes containing Alkali metals (Na, K, in particular) had the highest propensity for forming Cr(VI) fumes; in cases where Cr(VI) concentrations were very less, the K, Na levels were very less in the fumes, but were detected in the welding slag.
The main scope of this study is to enhance the knowledge of Chromium (VI) in welding fumes by addressing the problems in Chromium (VI) analysis, investigating the chemical forms of Chromium (VI) in different welding fumes, identifying factors affecting Chromium (VI) formation in welding fumes, and discussing the mitigation methods of Chromium (VI) in welding fumes.

Date of Award	13 Oct 2023
Original language	English
Awarding Institution	Teesside University
Sponsors	NSIRC & TWI Ltd (Cambridge)
Supervisor	Venkatesan Venkata Krishnan (Supervisor) & Geoff Melton (Supervisor)