Turbidimetric Spectroscopy for the Evaluation of Metalworking Fluids Stability

Abstract

The stability of oil-in-water (O/W) emulsions used as metalworking fluids is a key factor for the economical and environmental balance of the entire metalworking process because used and broken fluids must be recycled or disposed. In this study, the ability of turbidimetric spectroscopy in the ultraviolet and visible light range to detect metalworking fluids destabilization was evaluated. Destabilization was achieved by adding calcium chloride, thus achieving accelerated aging, which leads to coalescence, creaming, and complete emulsion separation. The stability of the metalworking fluids at 5% volumetric concentration in deionized water was monitored using a spectroscopic turbidimeter composed of an optical probe for in-line measurements. Destabilization was also monitored by measuring the vertical profile of backscattered and transmitted light. The results of this offline measurement system were compared with those from the in-line spectroscopic sensor, indicating that the latter can provide local, real-time information on emulsion destabilization, thus enabling control actions.

KEY WORDS:

• Metalworking Fluids
• Emulsion Stability
• Spectroscopy

ACKNOWLEDGEMENTS

The authors thank the Deutsche Forschungsgemeinschaft DFG and their Brazilian partners Financiadora de Estudos e Projetos FINEP, Conselho Nacional de Desenvolvimento Científico e Tecnológico CNPq, and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior CAPES within the BRAGECRIM program for funding parts of this research.

Review led by David Burris