Insight into the role of amines in Metal Working Fluids

• Main role of amines in oil/water metalworking emulsion was evaluated towards brass.
• The amines were studied both in pure water and in the 5% oil/water emulsion.
• Both the brass specimens and the oil/water emulsions were finely investigated.
• Tertiary amines were found to be less corrosive than primary ones in water.
• Cyclohexyldiethanolamine leads to stable lubricant emulsions limiting corrosion.

The influence of primary/tertiary amines in Oil-in-Water emulsions (as Metal Working Fluids (MWFs) towards brass) is evaluated in both pure water and 5% O/W emulsion. Physical properties, wetting, lubricating and corrosion behaviors are finely investigated. Experimental results show that the number of carbon atoms in amines plays a pivotal role in reducing the brass corrosion. Among the adopted amines, the cyclohexyldiethanolamine (CHDEA) seems to be the optimal one in both media: (i) it adsorbs easily onto the brass limiting corrosion and stain; (ii) it leads to stable emulsions; (iii) it does not affect the emulsion lubricant and wetting performances.

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